Kenco KT Series User manual

DDA Interface Manual
“KT” Series Magnetostrictive
Liquid Level Transmitters
Kenco Engineering Company
10001 East 54th Street
Tulsa, Oklahoma 74146
Phone: [phone]
Fax: [phone]
Website: www.kenco-eng.com
Email: [email protected]
79862
(Rev. #)
[5-2-19]

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DDA Interface Manual
Table of contents
1. Terms and Definitions.................................................................3
2. Introduction.................................................................................5
3. Safety Instructions......................................................................5
4. Quick Start-Up Guide..................................................................5
4.1 Before You Begin .................................................................. 5
4.2 Quick Start-Up Procedure ..................................................... 5
5. Display Menu..............................................................................5
5.1 Operation Modes................................................................... 5
5.1.1 Run Mode ...................................................................... 5
5.1.2 Program Mode............................................................... 5
5.2 Display Diagram.................................................................... 6
5.3 Menu Structure..................................................................... 6
6. Alarms.........................................................................................6
7. Error Codes (Faults)....................................................................7
8. DDA Interface..............................................................................7
9. Hardware and Software Environments.......................................8
10. DDA Command Decoder Examples ..........................................8
11. DDA/Host Computer Communication Protocol.........................9
12. DDA Command Definitions .....................................................13
12.1 Special Control Commands........................................... 13
12.2 Level Commands .......................................................... 13
12.3 Temperature Commands............................................... 14
12.4 Multiple Output Commands .......................................... 14
12.5 High-Level Memory Read Commands .......................... 15
12.6 High-Level Memory Write Commands .......................... 16
12.7 Diagnostic/Special Command Set ................................. 18
12.8 DDA Error Codes........................................................... 18
13. Dashboard, Setup Software ..................................... 19
13.1 Installing Dashboard..................................................... 19
13.2 Home Screen ................................................................ 19
13.3  ................................................................ 20
13.4 Signal Settings............................................................. 20
13.5 Level Settings .............................................................. 20
13.6 Temperature Settings................................................... 21
13.7 Flash Settings .............................................................. 21
13.8 Save Settings ............................................................... 22
13.9 Programming the Display ............................................ 22
13.9.1 Data from Device Tab........................................ 22
13.9.2 Calibration......................................................... 22
13.9.3 Factory.............................................................. 22

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DDA Interface Manual
1. Terms and definitions
6A Heavy Oils
‘Generalized Crude Oils’, Correction of Volume to 60 °F against API
Gravity.
6B Light Oils
‘Generalized Products’, Correction of Volume to
60 °F against API Gravity.
6C Chemical
‘Volume Correction Factors (VCF)’ for individual and special applica-
tions, volume correction to 60 °F against thermal expansion coeffi-
cients.
6C Mod
An adjustable temperature reference for defining VCF.
A
API Gravity
The measure of how heavy or light a petroleum liquid is compared to
water. Allowable values are 0 to 100 degrees API for (6A) and 0 to 85
degrees API for (6B).
D
DDA
‘Direct Digital Access’ – The digital protocol for use in intrinsically safe
areas.
Density
Mass divided by the volume of an object at a specific temperature. The
density value should be entered as lb. / cu. ft..
E
Explosion proof
Type of protection based on enclosure in which the parts which can
ignite an explosive gas atmosphere are placed within, and which can
withstand the pressure developed during an internal explosion of an ex-
plosive mixture, and which prevents the transmission of the explosion
to the explosive gas atmosphere surrounding the enclosure.
F
Flameproof
Type of protection based on enclosure in which the parts which can
ignite an explosive gas atmosphere are placed within and which can
withstand the pressure developed during an internal explosion of an ex-
plosive mixture, and which prevents the transmission of the explosion
to the explosive gas atmosphere surrounding the enclosure.
FOUNDATION™ fieldbus
An all digital, serial, two-way communications system that serves as
the base-level network in a plant or factory automation environment.
Developed and administered by the fieldbus FOUNDATION™.
G
GOVI
‘Gross Observed Volume of the Interface’ – The total volume of the tank
occupied by the interface liquid. The GOVI is only given when mea-
suring two liquids and is calculated by subtracting the volume of the
product from the total volume of liquid in the tank (GOVT – GOVP).
GOVP
‘Gross Observed Volume of the Product’ – The total volume of the tank
occupied by the product liquid. When measuring only one liquid, it is
also the total volume of liquid in the tank (GOVT). When measuring two
liquids it is the total volume of liquid in the tank minus the volume of
the interface liquid (GOVT – GOVI).
GOVT
‘Total Gross Observed Volume’ – The total volume of liquid in the tank.
When measuring only one liquid it is equal to the volume of the product
(GOVP). When measuring two liquids it is equal to the volume of the
product and interface liquids (GOVP + GOVI).
GOVU
‘Gross Observed Volume Ullage’ – the difference in volume between the
working capacity of a tank and the total volume in the tank (Working
Capacity – GOVT).
H
HART®
A Bidirectional communication protocol that provides data access
between intelligent field instruments and host systems.
I
Interface
Noun; The measurement of the level of one liquid when that liquid is
below another liquid.
Interface
Adj.; The Software Graphical User Interface (GUI) that allows the user
to access software protocols (HART, DDA, MODBUS).
Intrinsic safety
‘Intrinsically safe’ - Type of protection based on the restriction of
electrical energy within apparatus of interconnecting wiring exposed to
potentially explosive atmosphere to a level below that which can cause
ignition by either sparking or heating effects.

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DDA Interface Manual
M
Mass
The property of a body that causes it to have weight in a gravitational
field, calculated by density at the reference temperature multiplied by
the volume correction factor (Density * VCF).
MODBUS
A serial communications protocol published by Modicon in 1979 for use
with its programmable logic controllers (PLCs). It has become a de fac-
to standard communications protocol in industry, and is now the most
commonly available means of connecting industrial electronic devices.
N
NEMA Type 4X
A product Enclosure intended for indoor or outdoor use primarily to
provide a degree of protection against corrosion, windblown dust and
rain, splashing water, and hose-directed water; and to be undamaged by
the formation of ice on the enclosure. They are not intended to provide
protection against conditions such as internal condensation or internal
icing.
NPT
U.S. standard defining tapered pipe threads used to join pipes and
fittings.
NSVP
‘Net Standard Volume of the Product’ – The temperature corrected
volume for the product liquid in the tank, requires the transmitter to
be ordered with temperature measurement capabilities. The NSVP is
calculated by multiplying the volume of the product liquid by a volume
correction factor based on temperature (GOVP * VCF).
R
Reference Temperature
The temperature at which the density measurement is given, the allow-
able values are 32 °F to 150 °F (0 °C to 66 °C).
S
Specific Gravity
The density ratio of a liquid to the density of water at the same condi-
tions.
Sphere Radius
The internal radius of the sphere that contains the liquid, the value is
used to calculate the volume along with the Sphere Offset.
Sphere Offset
An offset value that accounts for additional volume in a sphere from
non-uniform sphere geometry, the value is used to calculate the volume
along with the Sphere Radius.
Strap Table
A table of measurement correlating the height of a vessel to the volume
that is contained at that height. The transmitter can contain up to 100
points.
T
TEC
‘Thermal Expansion Coefficient’ - a value correlating the change in tem-
perature for an object with the change in its volume. Allowable values
are 270.0 to 930.0. TEC units are in 10 E-6/Deg F.
Temperature Correction Method
One of five product correction methods used to correct the product
volume in the tank due to changes in temperature from 60 °F including
(6A, 6B, 6C, 6C Mod, and Custom Table.
V
Volume Calculation Mode
One of two methods use to calculate volume measurements from level
measurements, including Sphere and Strap Table.
VCF
‘Volume Correction Factor’ – A table of measurements correlating
temperature points with correction factors for the liquids expansion/
contraction. The transmitter can contain up to 50 points.
W
Working Capacity
The maximum volume of liquid that the user desires for their vessel to
hold, typically 80% of the vessels maximum volume before overfill.

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DDA Interface Manual
2. Introduction
2.1 Purpose and use of this manual
The content of this technical documentation and of its various
annexes is intended to provide information on mounting, installation
and commissioning by qualified service personnel according to
IEC 60079-14 and/or factory trained service technicians and local
regulations.
2.2 Used symbols and warnings
Warnings are intended for your personal safety and for avoidance
of damage to the described product or connected devices. In this
documentation, safety information and warnings to avoid dangers that
might affect the life and health of personnel or cause material damage
are highlighted by the preceding pictogram, which is defined below.
3. Safety instructions
3.1 Intended use
The purpose of this document is to provide detailed information on
the protocol interface. All safety related information is in the product
specific operation manual. Consult the operation manual before
connecting to the level transmitter.
4. Quick start-up guide
4.1 Before you begin
Note:
You must use a RS-485 converter with “Send Data Control” and the
Set-up Software to ensure proper operation.
Example:
B & B Electronics 485BAT3 (815-433-5100 www.bb-elec.com).
FTDI USB-RS485-WE-1800-BT (www.ftdichip.com)
4.2 Quick start-up procedure
1. Connect +24 Vdc to terminals.
2. Connect data lines to terminals.
3. Connect the PC (or other device) to data lines.
(If you are using a PC, use a RS-232 to RS-485 converter. See
Note above for more information.)
4. Turn on power to the transmitter.
5. Start the Dashboard. Select Com Port and Address. Factory
default address is ‘192 ’ for DDA.
Before starting the operation of the equipment read this documentation
thoroughly and follow the safety information.
Symbol Meaning
NOTICE This symbol is used to point to situations
that may lead to material damage and/or personal
injury.
6. Change the address to one that is suitable for the installation
network.
7. Verify proper operation of product and or interface floats and
temperature.
8. Turn off power to the transmitter.
9. Remove data lines.
10. Install the transmitter into the vessel (see Operation Manual).
11. Reconnect power and data lines.
12. Calibrate current tank level using setup software (optional).
13. Verify communications with the host system.
Default communication parameters
DDA: 4800 BAUD 8, E, 1
5. Display Menu
All liquid level transmitters are shipped with a Stylus (Kenco Part #
79857) to be used for manipulating the display. For single and dual
cavity housings, the Stylus is designed to allow for programming of the
unit without removing the housing. When using the Stylus make sure
to align the Stylus with the shape outline around the buttons in the same
orientation. Failure to correctly align the Stylus can cause the display to
not function properly.
Note:
Do not use any device other than the Stylus to operate the display.
Note:
Improper use of the Stylus can cause the display to not function
properly.
5.1 Operation Modes
The level transmitter runs in one of the following modes of operation.
You can use these modes to calibrate and set up various operating
parameters.
5.1.1 Run Mode
Run mode is the primary mode of operation. This mode will perform
measurements, display data, and respond to DDA commands.
5.1.2 Program Mode
Program mode is the primary mode for commissioning and trouble-
shooting the level transmitter. The full menu and available functions are
shown in section 5.3 Menu Structure. To enter program mode use the
Stylus and press the Enter Key as shown in section 5.2 Display Diagram.
Program Mode is protected by a password to keep unwarranted chan-
ges from occurring. The factory default password is 27513. When in
program mode, remote communications are not functional. An automa-
tic timeout feature is provided so that the transmitter does not remain
inadvertently in program mode. The timeout is set for 1 minute before
prompted for additional time. Total timeout is 2 minutes.

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DDA Interface Manual
Note:
Whenever program mode is exited from the display the unit will reset
itself to insure all changes have been accepted. The reset will take
approximately 5 seconds before the level transmitter is able to respond
to commands.
Note:
In program mode, the transmitter will not respond to incoming DDA
commands. A busy error will be sent to the controller to notify the
unit is in program mode. This function will prevent a user at a remote
terminal from programming the unit while a user is accessing program
mode from the display.
5.2 Display Diagram
UP Arrow – Used to move cursor on screen up and to increment num-
ber.
DOWN Arrow – Used to move cursor on screen down and to decrease
number.
SCROLL Arrow – Used to move cursor on screen to the right, cursor will
cycle back.
ENTER Key – Used to Enter Program Mode, select Highlighted Item, and

EXIT Key – Hidden key in the middle of the display that is used to exit
menu at any time.
MEASURED VARIABLE – The process variable that is selected to display.
The display will automatically scroll between selected variables.
MEASUREMENT – The numerical value for the MEASURED VARIABLE
shown on the display.
UNITs – Unit of measurement for the MEASURED VARIABLE shown on
the display.
TEMPERATURE – Average temperature for the product in the tank. Only
shown if the level transmitter was purchased with temperature.
NOTIFICATIONS – Four squares with letters. Top left square will always
be present indicating a D for DDA mode or a M for Modbus mode. Top
right square, A, will only show when there is an alarm. Toggle the UP
Arrow key to view alarms. Bottom right square, F, will only show when
there is a fault. Toggle the DOWN Arrow key to view error codes. Bot-
tom left square, P, will only show when the units is being programmed
remotely.
5.3 Menu Structure
• Data From Device
Display
Units
`Length Units
`Temp Units
Address
Signal Strength
`Prod Trig Lvl
`Int Trig Lvl
• Calibrate
Product Level
`Current Level
`Offset
Interface Level
`Current Level
`Offset
• Factory
Settings
`Gradient
`Serial Number
`HW Revision
`SW Revision
`SARA Blanking
`Magnet Blanking
`Gain
`Min Trig Level
Temp Setup

Auto Threshold
Reset to Factory
6. Alarms
The DDA output is equipped with several alarms that will be shown on
the display. Use the stylus to tap the Up arrow to view alarms. The
DDA output is set to fail high, greater than the order length, if there is an
issue and the level value output cannot be trusted.
Fig. 1: DDA Display

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DDA Interface Manual
101 Missing
Magnet


• Verify Float(s) are not in inactive zone.
• Verify Auto Threshold is enabled.
• Cycle power to sensor. If proper operation
is not restored, Contact Factory.
102 Internal
Fault 1
Cycle power to sensor. If proper operation
is not restored, Contact Factory.
103 Internal
Fault 2
Cycle power to sensor. If proper operation
is not restored, Contact Factory.
104 Internal
Fault 3
Cycle power to sensor. If proper operation
is not restored, Contact Factory.
105 Lobe Fault 1 • Verify Auto Threshold is enabled.
• Cycle power to sensor.
• If proper operation is not restored, Contact
Factory.
106 Lobe Fault 2 • Verify Auto Threshold is enabled.
• Cycle power to sensor.
• If proper operation is not restored,
Contact Factory.
107 Delta Fault Contact Factory to discuss application.
108 Internal
Fault 4
Cycle power to sensor. If proper operation
is not restored, Contact Factory.
109 Peak Fault • Verify Auto Threshold is enabled.
• Cycle power to sensor.
• If proper operation is not restored,
Contact Factory.
110 Hardware
Fault 1
Cycle power to sensor. If proper operation
is not restored, Contact Factory.
111 Power Fault • Cycle power to sensor.
• Verify Power Supply rating.
• Verify wiring.
• If proper operation is not restored,
Contact Factory.
112 Hardware
Fault 2
Cycle power to sensor. If proper operation
is not restored, Contact Factory.
113 Hardware
Fault 3
Cycle power to sensor. If proper operation
is not restored, Contact Factory.
114 Hardware
Fault 4
Cycle power to sensor. If proper operation
is not restored, Contact Factory.
115 Timing
Fault 1
Cycle power to sensor. If proper operation
is not restored, Contact Factory.
116 Timing
Fault 2
Cycle power to sensor. If proper operation
is not restored, Contact Factory.
117 Timing
Fault 3
Cycle power to sensor. If proper operation
is not restored, Contact Factory.
118 DAC Fault 1 Cycle power to sensor. If proper operation
is not restored, Contact Factory.
119 DAC Fault 2 Cycle power to sensor. If proper operation
is not restored, Contact Factory.
120 DAC Fault 3 Cycle power to sensor. If proper operation
is not restored, Contact Factory.
Fault
Code
Description Corrective Action
Fault
Code
Description Corrective Action
121 DAC Fault 4 Cycle power to sensor. If proper operation
is not restored, Contact Factory.
122 SPI Fault 1 Cycle power to sensor. If proper operation
is not restored, Contact Factory.
123 SPI Fault 2 Cycle power to sensor. If proper operation
is not restored, Contact Factory.
124 Setpoint
Fault
The analog setpoints are too close. Mini-
mum distance is 150 mm (6 in.) for analog
and 290 mm (11.5 in.) for SIL. Adjust
programmed setpoints as needed. (Analog
only) If proper operation is not restored,
Contact Factory.
125 Loop 1 Out
of Range
Verify that magnets are positioned within
expected measuring range. Adjust program-
med setpoints as needed. (Analog only) If
proper operation is not restored, Contact
Factory.
126 Loop 2 Out
of Range
Verify that magnets are positioned within
expected measuring range. Adjust program-
med setpoints as needed. (Analog only) If
proper operation is not restored, Contact
Factory.
127 EEPROM
Fault 1
Cycle power to sensor. If proper operation
is not restored, Contact Factory.
128 EEPROM
Fault 2
Cycle power to sensor. If proper operation
is not restored, Contact Factory.
129 Flash Failure Cycle power to sensor. If proper operation
is not restored, Contact Factory.
130 Internal
Error
Cycle power to sensor. If proper operation
is not restored, Contact Factory.
7. Error Codes (Faults)
8. DDA Interface
8.1 Data line termination and biasing
Termination and biasing of RS-485 data lines are as follows:
Biasing
Each transmitter uses a Fail-safe, Slew Rate-Limited RS-458/RS-422
Transceiver. No additional biasing resistors should be present on the
connecting devices (PLC, DCS, PC, Converter).
Termination
Each transmitter uses a Fail-safe, Slew Rate-Limited RS-
458/RS-422 Transceiver. No additional termination resistors are
necessary in the connecting devices (PLC, DCS, PC, Converter).
8.2 Communication parameters
The 2-wire differential communication interface and all data transmissi-
ons must be at half duplex. Only one device (either the master or a
single transmitter) can transmit data at any given time. BAUD rate
limitations are listed below.
DDA: 4800 BAUD 8, N, 1
(Reference) Monitor: DDA RTU Variable BAUD Rate 8, E, 1

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DDA Interface Manual
9. Hardware and software environments
The DDA digital transmitter operates in a networked, intrinsically safe
RS-485 DDA software environment. This environment supports up to
8 multi-dropped transmitters on one communication line. The network
requires a 4-wire bus to provide both power and communications to
each of the transmitters located in the hazardous area. The transmitters
are connected in multi-point configuration (see Figure 2).
The RS-485 network operates in a master/slave mode where the master
(host computer or similar type network controller) interrogates each
slave (DDA transmitter) for a specific type of data. Each slave has a
. . .
2
2
+24 Vdc
power
supply
RS-485
Examples:
PC, PLC, DCS
I.S.B.*
Approved intrinsic
safety barrier
(3 required)
General application
4-wire bus
Intrinsically
safe area
Maximum stub
length = 200 feet
Up to 8
transmitters
(DDA interface)
unique switch programmable hardware address that is issued by the
host computer to activate a particular transmitter. In addition, the DDA
hardware supports a command decoder that supports up to 128 different
commands. The host computer interrogates a transmitter for data by
sending an address byte, followed immediately by a command byte. The
addressed transmitter will ‘wake up’, identify itself by transmitting an
echo of its own local address followed by the received command, and
then perform the requested action. After the requested action has been
completed, the data (if any) will be transmitted back to the host computer
on the RS-485 network. Refer to Section 10 for ‘DDA Command decoder
examples’ and for more information.
10. DDA command decoder examples
10.1 Serial data transmission format
Example 1:
0X X X X X X X X P1
D1 bit Stop bit
Start bit Parity bit
D8 bit
After the DDA address decoder circuitry receives the 11-bit word, an
even parity check is performed across the 8-bit data field. If a parity error
is found, the word is ignored and the decoder circuitry resets for the next
transmission. If the parity check is good, the decoder circuitry checks for
a valid address byte. The address decoder circuitry uses the ‘D8’ bit to
distinguish the difference between address bytes and command bytes.
Address bytes are defined as having the most significant bit ‘D8’ set equal
to one. Valid address byte values include ‘C0’ hex to ‘FD’ hex (192 to
253 decimal). Address byte values from 80 hex to ‘BF’ hex are reserved
for future use, address byte values ‘FE’ and ‘FF’ hex are reserved for test
functions. (see Example 2).
Fig. 2: Typical Electrical Connections - Intrinsically Safe System

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DDA Interface Manual
10.2 Address byte
Example 2:
X X X X X X X 1
D8 bit = 1
(8-bit word - shown as D1 bit)
If the received address byte matches the local DDA address, the DDA
power supply circuitry is activated. If a valid address byte has been
found, the decoder circuitry checks to see if the next received word is a
command byte. Valid command byte values include ‘00’ hex to ‘7F’ hex
(0 to 127 decimal). In addition, all data byte values are restricted to be
within ‘00’ hex and ‘7F’ hex (see Example 3).
10.3 Command byte (and data bytes)
Example 3:
X X X X X X X 0
D8 bit = 1
(8-bit word - shown as D1 bit)
Again, an even parity check is performed on the command byte. If the
parity check is good, the eight bit data word is latched into a command
buffer. This buffer is read by the DDA software to determine which
command to execute. If the parity check fails, the command byte
is rejected and the old command (from the previous interrogation
sequence) will be left in the command buffer. The DDA hardware cannot
determine if the current command was possibly rejected. The host
computer must then verify if the correct command was received by
reading the echo of the address byte and command byte sent by the DDA
transmitter. This is the only guaranteed way to determine that both the
address and command bytes were received properly.
This method also insures proper verification, even if the parity check fails
to detect a multiple bit data error in either the address byte or command
byte. If the host computer determines that either the address byte or
command byte has been corrupted, it must wait the proper time-out
period and ignore the received message from the DDA transmitter that
was improperly interrogated. The time-out period is variable and is based
on the duration of the selected DDA command.
11. DDA/Host computer communication protocol
The DDA/Host computer communication protocol consists of two parts:
the interrogation sequence generated by the host computer and the
data response generated by the interrogated DDA transmitter. The host
interrogation sequence always consists of an address byte followed
immediately by a command byte (see Example 4).
11.1 DDA/Host communication
Example 4:
<address byte><command byte>
00 Hex to 7F Hex (0 to 127 decimal)
C0 Hex to FD Hex (192 to 253 decimal)
The maximum delay between the address byte and the command byte is
5 milliseconds. The DDA transmitter will not receive the new command
byte if this delay period is exceeded (and the old command byte will
be left in the command buffer). See previous section for additional
information on verification of the Address/Command bytes. An example
of an interrogation sequence to access a transmitter programmed for
address ‘F0’ hex (see Example 5).
The transmitter response consists of several components. After a
transmitter has been interrogated, the transmitter first responds by
transmitting its own local address and the command that was received
from the host computer. This re-transmission of the transmitter address
and received command serves two purposes. The first being a simple
identification that the correct transmitter received the correct command
and that it is currently active. The second purpose is to reset the DDA
Address/Command decoder circuitry for the next interrogation sequence.
11.2 Interrogation data sequence
Example 5:
<F0><0A>
Command 0A Hex (10 decimal)
Address F0 Hex (240 decimal)
Note:
If the DDA transmitter does not respond to the first interrogation by
the host, the Address/Command decoder will be left in an intermediate
state. If this occurs, the host will have to reinterrogate the respective
transmitter to reset the Address/Command decoder circuitry and then
interrogate the respective transmitter again to perform a new transmit-
ter measurement. This hardware feature must be considered when writ-
ing software communication drivers to access DDA transmitter data.

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DDA Interface Manual
After the DDA transmitter has retransmitted its local address and
received command, it will perform the requested measurement as
defined by the received command. After the requested measurement has
been completed, the data for that measurement will be transmitted to
the host in a predefined format including certain control characters. The
DDA transmitted data format begins with a ‘start of text’ ‘STX’ character
(STX = 02 hex). The ‘STX’ character set is immediately followed by
the requested data and then terminated with an ‘end of text’ ‘ETX’
character set (ETX = 03 hex). Certain commands allow multiple data
fields to be transmitted within one transmitted data sequence. For these
data transmissions, each data field is separated by an ASCII colon ‘:’
character (: = 3A hex), (see Examples 6 and 7).
Single field data transmission
Example 6:
<STX><dddd.ddd><ETX>
Multiple field data transmission
Example 7:
<STX><dddd.ddd:dddd.ddd:dddd.ddd><ETX>
All transmitted data will consist of 7-bit ASCII characters limited to hex
values between ‘00’ hex and ‘7F’ hex (i.e. data bit D8 = 0).
After a DDA transmitter has completed a data transmission, the
host must wait 50 milliseconds before another interrogation can
be performed. This delay is required to enable the previously
interrogated transmitter to go into sleep mode and release the network
communication lines.
All DDA control commands support a checksum calculation function,
Data Error Detection (DED) that allows the host computer (master) to
check the integrity of the transmitted data. The actual checksum value
that is transmitted is the compliment (2’s compliment) of the calculated
value. The checksum scheme is based on a 16-bit summation of the hex
data within the transmitted block (including ‘STX’ and ‘ETX’ character
sets) without regard to overflow. The two byte result of the adding
process is then complimented and appended to the transmitted data
block.
This compliment process makes the final checksum comparison more
efficient in that the checksum result added to its compliment will always
result in a zero sum for uncorrupted data transmissions. Checksum
data (two hex bytes) can range from ‘0000’ hex to ‘FFFF’ hex. Since the
communication network only allows transmitted data values between
‘00’ and ‘7F’ hex, special processing is required on the hex checksum
value before it can be transmitted.
This two byte hex value must first be converted to numeric (decimal)
ASCII characters before transmission. For example, a checksum value
of ‘FFFF’ hex would be transmitted as ASCII 65535. The host computer
would then have to convert ASCII 65535 back to FFFF hex and perform
its own checksum calculation and comparison for the received data
from the DDA transmitter. An example is shown (see Example 8) of a
single field data transmission including checksum data and an sample
checksum calculation.
Example 8:
<STX><dddd.ddd><ETX><ccccc>
Append checksum value
Note:
The appended checksum value will always consist of five decimal (AS-
CII) characters ranging from 00000 to 65535. The checksum function
can be enabled or disabled.
Message transmitted from DDA transmitter (command 12 Hex):
<STX><265.322.109.456><ETX>64760
Hex character equivalent of transmitted data record including <STX>
and <ETX> characters:
02, 32, 36, 35, 2E, 33, 32, 32, 3A, 31, 30, 39, 2E, 34, 35, 36, 03
Two byte Hex summation of data: 0308 Hex
Two’s compliment: FCF8 Hex
Convert to decimal ASCII: 64760
To verify transmitted data from the DDA transmitter, perform the two byte
Hex summation over the data record (including ‘<STX>’ and ‘<ETX>’)
shown in (Example 8). The result in this example is 0308 Hex. Then
convert the decimal ASCII checksum value back to Hex (for example,
64760 to FCF8 Hex). Add the Hex summation value to the Hex checksum
value and the result will be zero (disregarding overflow) for uncorrupted
data. 0308 Hex + FCF8 Hex = 0000 Hex.
Note:
Cyclic Redundancy Check (CRC) error checking will be offered at a
later date. A command switch will be defined that will let the DDA data
be transmitted with CRC error checking instead of checksum error
checking. The checksum calculations will use the CRC-CCITT defined
polynomial with a 16-bit CRC result. This 16-bit CRC value will be
appended to each transmitted message. Since the communication net-
work only allows transmitted data values between 00 and 7F hex, spe-
cial processing is required on the 16-bit hex CRC value before it can be
transmitted. This 16-bit (two byte) hex value must first be converted to
numeric (decimal) ASCII characters before transmission. For example,
a checksum value of ‘FFFF’ hex would be transmitted as ASCII 65535.
Checksum Calculation

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DDA Interface Manual
11.3 Network protocol/timing considerations
The DDA network has several timing constraints that must be considered
when designing and coding communication drivers. The DDA network
follows the RS-485 standard which defines a multi-drop communication
interface that uses differential drivers and receivers operating in half-
duplex mode. When using the RS-485 standard configuration, each
device’s driver and receiver are wired together (see Figure 3).
Each device drive on the network must be disabled (high impedance)
except when the device is ready to transmit data. In order to keep
devices from transmitting data at the same time, one device is selected
as the host (or master). In a DDA network, the host computer (or other
communication interface) is the master, and controls the communication
timing and protocol. The DDA transmitters act as slave devices, only
transmitting data when requested by the host computer device. In this
case, the host computer enables its driver and transmits the ‘Address/
Command’ interrogation sequence.
After the Address/Command has been completely transmitted, the
host disables its driver to allow reception of the data from the DDA
transmitter. The transmitter with the matching address then becomes
active, enables its driver and transmits the Address/Command echo
followed by the requested data.
The transmitter then disables its driver and goes back into sleep mode.
Since all devices operate independently, certain timing constraints are
imposed on the protocol to eliminate multiple devices from transmitting
data simultaneously.
Network protocol timing sequences (interrogation sequences) are
shown in (Figure 4). This time line representation of data transmission
sequences also provides information about host computer control of the
RS-485 communication card and also illustrates driver enabled control
through the RTS control line.
Note:
Many available communication cards (line drivers) for use with the host
computer device use a special control line input to control the enabling
and disabling of the RS-485 driver. Typically this input is connected
to the computers RTS or DTR communication port control line. The
computer can then control the state of the driver by toggling the RTS
or DTR signal lines via software control. An example of this control
method is shown in (Figure 4). Other control methods are also used
depending on the manufacturer of the equipment.
DDA
transmitter
Microprocessor
Host
computer
Enable
control
Data
IN
Data
OUT
(RX/TX+)
(RX/TX-)
To other
DDA transmitters
DDA
transmitter
Microprocessor
Fig. 3: RS-485 Multi-drop example
T1 T5
T2
T3
T4
T6 T7
T8
T9
T10
T12
T11
DataCommandAddress
Command
Address
T0
RTS control
of host driver
Data
transmitted
by host
device
Data
transmitted
by DDA
transmitter
Fig. 4: Network protocol timing information
The following steps provide an interrogation sequence example:
1. The start of the sequence begins when the host enables its
RS-485 driver to transmit the Address/Command bytes
(see time line ‘T0’ in Figure 4).
2. After the driver is enabled, the host performs a small time
delay ‘T1’. In this example, the host enables the driver
by raising the RTS control line of the computer to the active
(enabled) state. This typically requires no more than 1 milli-
second. If the communication lines are extremely long,
additional time may be required due to the additional
capacitance of the wires.
3. The host then transmits the address byte followed immediately by the
command byte. For 4800 Baud transmission
rates, the time to transmit one byte (11-bit word size) is
fixed at 2.3 milliseconds. Then time delays ‘T2’ and ‘T4’ are
fixed at 2.3 milliseconds. Time delay ‘T3’ is the interbyte
transmission time. Normally this is at least one bit time
(0.21 milliseconds @ 4800 Baud) which is controlled by
the computer communication hardware. Sometimes
software overhead can extend this delay. The maximum
permissible delay for period ‘T3’ is 5 milliseconds. Then the
total maximum delay for periods ‘T2, T3, T4’ is 9.6 milliseconds.
4. After the host transmits the address and command bytes, the
host disables its driver to allow the transmitter to transmit the

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DDA Interface Manual
Address/Command echo and the requested data.
Before the driver is disabled, the software must insure that
the command byte has been completely transmitted. This can
be done by observing control flags from ‘UART’ of the
communication port, such as Transmit Register Empty (TRE)
and Transmit Holding Register Empty (if the UART is double
buffered). Software delay methods based on maximum
character transmission times for 4800 Baud rates can also be
used but are less reliable. Once it has been verified that the
command byte ‘0’ has been completely transmitted, an
additional delay should be added before the driver is disabled.
This delay ‘T5’ will insure that data has propagated the
network wiring before the driver goes to the high impedance
(disabled) state. A delay period of ‘T5’ = 1 millisecond is
adequate for most long cable runs. The maximum delay
allowed for ‘T5’ is based on the fact that time period ‘T6’ is
fixed in the DDA hardware to be 22 (+/-2) milliseconds. The
host driver should be disabled well before (at least 5
milliseconds) the DDA transmitter enables its driver and
begins transmission of the Address/Command echo.
Assuming the maximum delay of 5 milliseconds for period
‘T3’, and 2.3 milliseconds for ‘T4’, and that the host driver
should be disabled for 5 milliseconds before the transmitter
begins transmitting data, the maximum delay for ‘T5’ then is
7.7 milliseconds.
Note:
If ‘T3’ is less than 5 milliseconds, then the maximum delay for ‘T5’ can
be extended by the difference (5 milliseconds - T3 actual).
5. The transmitter will begin to transmit the Address/Command
echo in 22 (+/- 2) milliseconds after the address byte is
received from the host computer. This is defined as period
‘T6’ and is fixed by the DDA hardware. Based on a Baud rate
of 4800, the address echo is transmitted in 2.3 milliseconds
(period ‘T7’). The interbyte delay period ‘T8’ for the DDA
transmitter is fixed at 0.1 milliseconds and the command
echo is transmitted 2.3 milliseconds (period ‘T9’).
6. Period ‘T10’ is the time required for the DDA electronics
to perform the requested command. This is a variable
delay based on the command requested. The typical
transmitter response time for each command is listed in
section ‘12 DDA command definitions’.
7. Period ‘T11’ is the time required for the DDA electronics to
transmit the data for the requested command. This is a
variable delay based on the command requested. The
typical data transmission time for each command is listed
in section ‘12 DDA command definitions’.
8. After the transmitter has completed the data transmission
for the requested command, it will disable its driver and
go back to inactive mode. The transmitter electronics
require 50 milliseconds to transition from active mode to
inactive mode. Another transmitter (or the same transmitter)
cannot be interrogated until time period ‘T12’ = 50 milli-
seconds has elapsed.
9. Repeat the sequence for the next transmitter. Sequences also
provide information about host computer control of the RS-485
communication card and also illustrates driver enabled control
through the RTS control line.
Other protocol considerations
1. The transmitted ASCII data from the DDA transmitter may
contain data fields with ‘Exxx’ error codes. All DDA error codes
are preceded by ASCII ‘E’ (45 hex, 69 decimal). Communica-
tion interface drivers must parse and handle DDA error codes
properly or data processing errors could result. For additional
information about DDA error codes, (see section 12.8 ).
2. Use the DDA ‘Data Error Detection’ function to verify the
integrity of the data transmitted from the transmitter.
3. Certain RS-485 communication cards and (RS-232 to RS-485
converter cards) allow user control of the receiver function.
This feature must be considered when developing com-
munication drivers. Due to the half-duplex RS-485 loopback
wire connections, all data that is transmitted by the host
computer device will be ‘echoed’ into the receiver inputs.
If the receiver function is enabled, then the host transmitted
data along with the DDA transmitted data will be
received into the computer receive buffer.

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DDA Interface Manual
12. DDA Command definitions
12.1 Special control commands
Command 00 Hex (0 Dec) - Transmitter disable command
This command can be used to disable an active transmitter (force
transmitter back to sleep mode). This command does not need to
be preceded by an address byte and can only be issued when DDA
transmitters are not transmitting data. This ‘disabled’ command is
typically used with other commands that could leave the transmitter
in active mode, i.e. certain memory transfer commands, test mode
commands, etc.
Note:
During normal mode operation, a DDA transmitter will force itself back
into sleep mode if any data is transmitted on the network by any other
device. This is a safety feature added to the firmware to avoid data
collisions on the network.
Command 01 Hex (1 Dec): Module identification command
Data format: <STX><DDA><ETX><ccccc>
• Fixed length record containing 3 ASCII characters ‘<DDA>’
• Five (5) character checksum appended after ‘<ETX>’ character set
Command 02 Hex (2 Dec): Change address
Data format: <SOH><ddd><EOT>
• Fixed length record with three (3) characters
• The data field is the new address
• The data range is the new address
• The data range is from 192 - 253
• ‘<SOH>’ is ASCII 01 Hex
• ‘<EOT>’ is ASCII 04 Hex
• Default Address is ‘192’
Command 03 Hex - Command Hex 09 - Not Defined
12.2 Level commands
Command 0A Hex (10 Dec): Output level 1 (product) at 0.1 inch
resolution (with checksum)
Data format: <STX><dddd.d><ETX><ccccc>
• Variable length record with one (1) to four (4) characters to the left
of decimal character
• Fixed at one (1) character to the right of decimal character
• Five (5) character checksum appended after the ‘<ETX>’ character
set
Note:
<ccccc> Checksum characters are only appended if the Data Error
Detection (DED) function is enabled.
Command 0B Hex (11 Dec): Output level 1 (product) at 0.01 inch
resolution (with checksum)
Data format: <STX><dddd.dd><ETX><ccccc>
• Variable length record with one (1) to four (4) characters to the left
of decimal character
• Fixed at two (2) characters to the right of decimal character
• Five (5) character checksum appended after the ‘<ETX>’ character
set
Command 0C Hex (12 Dec): Output level 1 (product) at
0.001 inch resolution (with checksum)
Data format: <STX><dddd.ddd><ETX><ccccc>
• Variable length record with one (1) to four (4) characters to the left
of decimal character
• Fixed at three (3) characters to the right of decimal character
• Five (5) character checksum appended after ‘<ETX’> character set
Command 0D Hex (13 Dec): Output level 2 (interface) at 0.1 inch
resolution (with checksum)
Data format: Same as Command 0A
Command 0E Hex (14 Dec): Output level 2 (interface) at 0.01 inch
resolution (with checksum)
Data format: Same as Command 0B
Command 0F Hex (15 Dec): Output level 2 (interface) at 0.001 inch
resolution (with checksum)
Data format: Same as Command 0C
Command 10 Hex (16 Dec): Output level 1 (product) and level 2
interface at 0.1 inch resolution
(with checksum)
Data format: <STX><dddd.d:dddd.d><ETX><ccccc>
• Variable length record with one (1) to four (4) characters to the left
of each decimal character in each data field
• Fixed at one (1) character to the right of each decimal character in
each data field
• Level 1, level 2 data fields separated by ASCII colon (:) character
• Five (5) character checksum appended after the ‘<ETX>’ character
set
Command 11 Hex (17 Dec): Output level 1 (product) and level 2
(interface) at 0.01 inch resolution
(with checksum)
Data format: <STX><dddd.dd:dddd.dd><ETX><ccccc>
• Variable length record with one (1) to four (4) characters to the left
of each decimal character in each data field
• Fixed at two (2) characters to the right of each decimal character in
each data field.
• Level 1, level 2 data fields separated by ASCII colon (:) character
• Five (5) character checksum appended after the ‘<ETX>’ character
set
Command 12 Hex (18 Dec): Output level 1 (product) and level 2
(interface) at 0.001 inch resolution
(with checksum)
Data characters can include the following:
• 0 through 9
• (-) minus sign
• (.) decimal point
• (E) ASCII 45 Hex precedes all error codes
• (:) ASCII 3A Hex is used as a data field separator for multiple data
field transmissions
• (space) ASCII 20 Hex space character

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DDA Interface Manual
Data format: <STX><dddd.ddd:dddd.ddd><ETX><c-
cccc>
• Variable length record with one (1) to four (4) characters to the left
of each decimal character in each data field
• Fixed at three (3) characters to the right of each decimal character in
each data field
• Level 1, level 2 data fields separated by ASCII colon (:) character
• Five (5) character checksum appended after the ‘<ETX>’ character
set
Command 13 Hex - Command 18 Hex - Not Defined
12.3 Temperature commands
Command 19 Hex (25 Dec): Average Temperature at 1.0 °F resolution
(with checksum)
Data format: <STX><dddd><ETX><ccccc>
• Variable length record with one (1) to four (4) characters
• Five (5) character checksum appended after the ‘<ETX>’ character
set
Note:
Average temperature is the average temperature reading from all DTs sub-
merged by approximately 1.5 inches of product.
Command 1A Hex (26 Dec): Average temperature at 0.2 °F resolution
(with checksum)
Data format: <STX><dddd.d><ETX><ccccc>
• Variable length record with one (1) to four (4) characters to the left
of decimal character
• Fixed at one (1) character to the right of decimal character
• Five (5) character checksum appended after the ‘<ETX>’ character
set
Command 1B Hex (27 Dec): Average temperature at 0.02 °F resolution
(with checksum)
Data format: <STX><dddd.dd><ETX><ccccc>
• Variable length record with one (1) to four (4) characters to the left
of decimal character
• Fixed at two (2) characters to the right of decimal character
Five (5) character checksum appended after the ‘<ETX>’ character set
Command 1C Hex (28 Dec):
Individual DT temperature at 1.0 °F resolution (with checksum)
Data format:
<STX><dddd:dddd:dddd:dddd:dddd><ETX><ccccc>
• Variable length record with one (1) to four (4) characters in each
data field
• Variable number of data fields (up to 5) separated by ASCII colon
(:) characters. Number of data fields is based on the number of DTs
programmed in DDA transmitter memory
• First data field is always DT #1, second data field is DT #2, etc
• Five (5) character checksum appended after the ‘<ETX>’ character
set
Command 1D Hex (29 Dec):
Individual DT temperature at 0.2 °F resolution (with checksum)
Data format:
<STX><dddd.d:dddd.d:dddd.d:dddd.d:dddd.d><ETX><ccccc>
• Variable length record with one (1) to four (4) characters to the left
of decimal character in each data field
• Fixed at one (1) character to the right of each decimal character in
each data field
• Variable number of data fields (up to 5) separated by ASCII colon
(:) characters. Number of data fields is based on the number of DTs
programmed in DDA transmitter memory
• First data field is always DT #1, second data field is DT #2,...etc
• Five (5) character checksum appended after the ‘<ETX>’ character
set
Command 1E Hex (30 Dec):
Individual DT temperature at 0.02 °F resolution (with checksum)
Data format:
<STX><dddd.dd:dddd.dd:dddd.dd:dddd.dd:dddd.dd><ETX><c-
cccc>
• Variable length record with one (1) to four (4) characters to the left
of decimal character in each data field
• Fixed at two (2) characters to the right of each decimal character in
each data field
• Variable number of data fields (up to 5) separated by ASCII colon
(:) characters. Number of data fields is based on the number of DTs
programmed in DDA transmitter memory
• First data field is always DT#1, second data field is DT #2,...etc
• Five (5) character checksum appended after the ‘<ETX>’ character
set
Command 1F Hex (31 Dec):
Average and individual DT temperature at 1.0 °F resolution
(with checksum)
Data format:
<STX><dddd:dddd:dddd:dddd:dddd:dddd><ETX><ccccc>
• Variable length record with one (1) to four (4) characters in each
data field
• Variable number of data fields (up to 6) separated by ASCII colon (:)
characters. The number of data fields is based on the number of DTs
programmed in DDA transmitter memory (number of DTs + 1)
• The first data field is always the average of the individual DTs
submerged by at least 1.5 inches of product
• The second data field is always DT #1, third data field is DT #2, ...
etc
• Five (5) character checksum appended after the ‘<ETX>’ character
set
12.4 Multiple Output Commands (Level and Temperature)
Command 28 Hex (40 Dec): Level 1 (product) at 0.1 inch resolution,
and average temperature at 1.0 °F
resolution (with checksum)
Data format: <STX><dddd.d:dddd><ETX><ccccc>
• Variable length record with one (1) to four (4) characters to the left
of decimal character in first data field
• Fixed at one (1) character to the right of decimal character in first
data field
• Variable length record with one (1) to four (4) characters in second
data field
• Level 1 temperature data fields separated by ASCII colon (:)
character
• Five (5) character checksum appended after the ‘<ETX>’ character
set

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DDA Interface Manual
12.4 Multiple Output Commands (continued)
Command 29 Hex (41 Dec): Level 1 (product) at 0.01 inch resolution,
and average temperature at 0.2 °F
resolution (with checksum)
Data format: <STX><dddd.dd:dddd.d><ETX><ccccc>
• Variable length record with one (1) to four (4) characters to the left
of decimal character in first data field
• Fixed at two (2) characters to the right of decimal character in first
data field
• Variable length record with one (1) to four (4) characters to the left
of decimal character in second data field
• Fixed at one (1) character to the right of decimal character in second
data field
• Level 1, temperature data fields separated by ASCII colon (:)
character
• Five (5) character checksum appended after the ‘<ETX>’ character
set
Command 2A Hex (42 Dec): Level 1 (product) at 0.001 inch resolution,
and average temperature at 0.02 °F
resolution (with checksum)
Data format: <STX><dddd.ddd:dddd.dd><ETX><ccccc>
• Variable length record with one (1) to four (4) characters to the left
of decimal character in first data field
• Fixed at three (3) characters to the right of decimal character in first
data field
• Variable length record with one (1) to four (4) characters to the left
of decimal character in second data field
• Fixed at two (2) characters to the right of decimal character in
second data field
• Level 1, temperature data fields separated by ASCII colon (:)
character
• Five (5) character checksum appended after the ‘<ETX>’ character
set
Command 2B Hex (43 Dec):
Level 1 (product), level 2 (interface) at 0.1 inch
resolution, and average temperature at 1.0 °F
resolution (with checksum)
Data format: <STX><dddd.d:dddd.d:dddd><ETX><ccccc>
• Variable length record with one (1) to four (4) characters to the left
of decimal character in first data field
• Fixed at one (1) character to the right of decimal character in first
data field
• Variable length record with one (1) to four (4) characters to the left
of decimal character in second data field
• Fixed at one (1) character to the right of decimal character in second
data field
• Variable length record with one (1) to four (4) characters in third
data field
• Level 1, level 2, temperature data fields separated by ASCII colon (:)
character
• Five (5) character checksum appended after the ‘<ETX>’ character
set
Command 2C Hex (44 Dec):
Level 1 (product), level 2 (interface) at 0.01 inch
resolution, and average temperature at 0.2 °F
resolution (with checksum)
Data format: <STX><dddd.dd:dddd.dd:dddd.d><ETX><ccccc>
• Variable length record with one (1) to four (4) characters to the left
of decimal character in first data field
• Fixed at two (2) characters to the right of decimal character in first
data field
• Variable length record with one (1) to four (4) characters to the left
of decimal character in second data field
• Fixed at two (2) characters to the right of decimal character in
second data field
• Variable length record with one (1) to four (4) characters to the left
of decimal character in third data field.
• Fixed at one (1) character to the right of decimal character in third
data field
• Level 1, level 2, temperature data fields separated by ASCII colon (:)
character
• Five (5) character checksum appended after the ‘<ETX>’ character
set
Command 2D Hex (45 Dec): Level 1 (product), level 2 (interface) at 0.001
inch resolution, and average temperature at 0.02 °F resolution (with
checksum)
Data format: <STX><dddd.ddd:dddd.ddd:dddd.dd><ETX><ccccc>
• Variable length record with one (1) to four (4) characters to the left
of decimal character in first data field
• Fixed at three (3) characters to the right of decimal character in first
data field
• Variable length record with one (1) to four (4) characters to the left
of decimal character in second data field
• Fixed at three (3) characters to the right of decimal character in
second data field
• Variable length record with one (1) to four (4) characters to the left
of decimal character in third data field
• Fixed at two (2) characters to the right of the decimal character in
third data field
• Level 1, level 2, temperature data fields separated by ASCII colon (:)
character
• Five (5) character checksum appended after the ‘<ETX>’ character
set
Command 2E Hex - Command 30 Hex - Not Defined
Command 31 Hex - Command 40 Hex - Reserved for factory use
12.5 High-level memory read commands
Command 4B Hex (75 Dec): Read ‘number of floats and number of DTs’
control variables
Data format: <STX><d:d><ETX><ccccc>
• Fixed length record with one (1) character in each field
• The first data field is the number of floats, second data field is the
number of DTs
• Five (5) character checksum appended after the ‘<ETX>’ character
set
Command 4C Hex (76 Dec): Read ‘gradient’ control variable
Data format: <STX><d.ddddd><ETX><ccccc>
• Fixed length record with seven (7) characters (including decimal
point)
• Five (5) character checksum appended after the ‘<ETX>’ character
set

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DDA Interface Manual
Command 4D Hex (77 Dec): Read float zero position data
(float #1 and #2)
Data format: <STX><dddd.ddd:dddd.ddd><ETX><ccccc>
Command 4D Hex (77 Dec) (continued):
• Variable length record with one (1) to four (4) characters to the left
of decimal character in first data field. The data may include an ASCII
(-) negative sign character (2D Hex) in the first character position
• Fixed at three (3) characters to the right of decimal character in first
data field
• Variable length record with one (1) to four (4) characters to the
left of decimal character in second data field. The data may include
an ASCII(-) negative sign character (2D Hex) in the first character
position
• Fixed at three (3) characters to the right of decimal character in
second data field
• Float #1, float #2 data fields separated by ASCII colon (:) character
• Five (5) character checksum appended after the ‘<ETX>’ character
set
Command 4E Hex (78 Dec):
Read DT position data (DTs 1 - 5)
Data format:
<STX><dddd.d:dddd.d:dddd.d:dddd.d:dddd.d><ETX><ccccc>
• Variable length record with one (1) to four (4) characters to the left
of decimal character in each data field
• Fixed at one (1) character to the right of decimal character in each
data field
• Variable number of data fields (up to 5) separated by ASCII colon
(:) characters. The number of data fields is based on the ‘number of
DTs’ control variable. (see command 4B Hex)
• The first data field is always DT #1, second field is always DT #2,...
etc.
• Five (5) character checksum appended after the ‘<ETX>’ character
set
Note:
DT position data is referenced from the mounting flange of the transmitter
housing. DT #1 is the DT closest to the tip of the transmitter.
Command 4F Hex (79 Dec):
Read factory serial number data and software version number
Data format:
<STX><ddddd....ddddd:Vd.ddd><ETX><ccccc>
• Fixed length record of 50 characters to the left of the colon character
and 6 characters to the right of the colon character (57 total)
• Five character checksum appended after the ‘<ETX>’ character set
Command 50 Hex (80 Dec):
Read firmware control code #1
Data format:
<STX><d:d:d:d:d:d><ETX><ccccc>
• Fixed length record with one (1) character in each data field
• First data field is the control variable for the data error detection
(DED) mode
• The second data field is the control variable for the communication
time-out timer (CTT)
• The third data field is the control variable for temperature data units
• The fourth data field is the control variable for linearization enable/
disable
• The fifth data field is the control variable for innage/ullage level
output
• The sixth data field is reserved for future use; the output value for
this field is ASCII ‘0’
• See write command (5A Hex) for field value assignments
• Five (5) character checksum appended after the ‘<ETX>’ character
set
Command 51 Hex (81 Dec): Read hardware control code #1
Data format: <STX><dddddd><ETX><ccccc>
• Fixed length record with six (6) characters
• The hardware control code controls various functions in the DDA
electronic hardware
• The hardware control code must match the hardware control code
stamped on the transmitter label; the control code on the label is
preceded by ‘CC’ (for example, CC001122)
• Five (5) character checksum appended after the ‘<ETX>’ character
set
• For additional information about the hardware control code, (see
section 4, Quick Start-up Guide Modbus and DDA)
Command 52 Hex (82 Dec): Not defined
Command 53 Hex (83 Dec): Reserved for factory use
Command 54 Hex (84 Dec): Not defined
12.6 High-level memory write commands
Command 55 Hex (85 Dec): Write ‘number of floats and number of
DTs’
control variables
Host Issued Command (Part 1)
Data format: <addr><commands>
• ‘<addr>’ is the DDA transmitter address
• ‘<command>’ is DDA command 55
• After the address and command byte have been transmitted by the
host, the respective DDA transmitter will ‘wake up’ and retransmit
(echo) the local DDA address and received command. The DDA
transmitter will remain active, waiting for the second part of the
memory write command to be issued by the host. If the second
part of the memory write command is not received within 1.0
seconds (see note below), or the command is not received in the
proper format, the DDA transmitter will cancel the current command
sequence and go back to sleep mode.
Note:
The time-out timer function can be enabled or disabled.
Host Issued Command (Part 2)
Data format: <SOH><d:d><EOT>
• Fixed length record with two (2) data fields
• ‘<SOH>’ is ASCII 01 Hex
• The first data field contains the ‘number of floats’ value to be written
to the ‘number of floats’ control variable. This variable is limited to a
value of 1 or 2 (ASCII)
• The second data field contains the ‘number of DTs’ value to be
written to the ‘number of DTs’ control variable. This variable is
limited to a value between 0 and 5 (ASCII)

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DDA Interface Manual
• ASCII colon (:) is the ‘number of floats/number of DTs’ field
separator
• ‘<EOT>’ is ASCII 04 Hex
DDA Transmitter Response (verification sequence)
Data format: <STX><d:d><ETX><ccccc>
• Fixed length record with two (2) data fields
• ‘<STX>’ is ASCII 02 Hex
• The first data field contains the ‘number of floats’ value to be written
to the ‘number of floats’ control variable. This variable is limited to a
value of 1 or 2 (ASCII)
• The second data field contains the ‘number of DTs’ value to be
written to the ‘number of DTs’ control variable. This variable is
limited to a value between 0 and 5 (ASCII)
• ASCII colon (:) is the ‘number of floats/number of DTs’ field
separator
• ‘<ETX>’ is ASCII 03 Hex
• ‘<ccccc>’ is a five (5) character checksum appended after the
‘<ETX>’ character set
Host Issued Command (Part 3)
Data format: <ENQ>
• ‘<ENQ>’ is ASCII 05 Hex. This character set is sent by the host
to initiate the EEPROM write cycle. After the EEPROM memory
locations have been successfully written to, the DDA transmitter
will respond back to the host with a ‘ACK’ character set signifying
the memory write cycle was successful, or with a ‘NAK’ character
signifying the memory write cycle was unsuccessful. See DDA
transmitter response below
• EEPROM write time is 10 milliseconds per byte. The ‘ACK/NAK’
response will not be transmitted by the DDA transmitter until the
memory bytes have been written and verified or a memory write
error has caused the DDA transmitter to time-out
Note:
EEPROM write time is 10 milliseconds per byte. The ACK/NAK response
will not be transmitted by the DDA transmitter until the memory bytes
have been written and verified or a memory write error has caused the
DDA transmitter to time-out.
DDA Transmitter Response:
Data format: <ACK>
• ‘<ACK>’ is ASCII 06 Hex. This character set is sent by the DDA
transmitter to confirm to the host that the EEPROM memory write
cycle was completed successfully
Data format: <NAK><Exxx><ETX><ccccc>
• ‘<NAK>’ is ASCII 15 Hex. This character set is sent by the DDA
transmitter to confirm to the host that the EEPROM memory write
cycle was not completed successfully
• ‘<Exxx>’ is an error code defining the memory write error that
occurred during the EEPROM write cycle. ‘E’ is ASCII 45 Hex and
‘xxx’ is the numeric ASCII error code ranging from 000 to 999. For
additional information about DDA error codes, (see section 12.8).
• ‘<ETX>’ is ASCII 03 Hex
• ‘<ccccc>’ is a five character checksum appended after the ‘<ETX>’
character set
• Value can range from 00000 to 65535.
All high level memory write commands adhere to
the communication sequence as described above,
and consist of the following six components:
1. Host issued command (Part 1): <address><command>
2. DDA transmitter response: <address><command> echo
3. Host issued command (Part 2):
data to be written (including necessary control characters)
4. DDA transmitter response: verification sequence
5. Host issued command (Part 3): <ENQ>
6. DDA transmitter response: <ACK> or <NAK>
Descriptions for other high level memory write commands will include
only the Data format for Part 2 of each host issued command.
Command 56 Hex (86 Dec): Write ‘gradient’ control variable
Data format: <SOH><d.ddddd><EOT>
• Fixed length record with one data field
• ‘<SOH>’ is ASCII 01 Hex
• The fixed length data field contains the ‘gradient’ value to be written
to the ‘gradient’ control variable. This variable is limited to a value
between 7.00000 and 9.99999 (ASCII)
• ‘<EOT>’ is ASCII 04 Hex
Command 57 Hex (87 Dec): Write float zero position data
(float #1 or #2)
Data format: <SOH><c:dddd.ddd><EOT>
• Variable length record with two (2) data fields
• The first data field contains one character that controls which zero
position memory location is written to (i.e., float #1 or float #2). This
control character is limited to a value of 1 or 2 (ASCII)
• The second data field contains the ‘zero position’ data value to be
written to the ‘zero position’ memory location. This is a variable
length data field with one (1) to four (4) characters to the left of the
decimal character and fixed at three (3) characters to the right of the
decimal character. The data may include the ASCII (-) negative sign
character (2D Hex) in the first position. The zero position data is
limited to a value between -999.999 and 9999.999 (ASCII)
• ‘<EOT>’ is ASCII 04 Hex
Note:
Zero position is referenced from the mounting flange of the transmitter
housing.
Command 58 Hex (88 Dec): Write float zero position data
(float #1 or #2) using DDA calibrate mode.
Data format: <SOH><c:dddd.ddd><EOT>
• Variable length record with two (2) data fields
• The first data field contains one character that controls which zero
position memory location is written to (i.e., float #1 or float #2). This
control character is limited to a value of 1 or 2 (ASCII)
• The second data field contains the ‘current float position’ data value
to be used to calculate the ‘zero position’ value that is to be written
to the ‘zero position’ memory location. This is a variable length data
field with one (1) to four (4) characters to the left of the decimal
character and fixed at three (3) characters to the right of the decimal
character. The data may include the ASCII (-) negative sign character
(2D Hex) in the first position. The ‘current float position’ data is
limited to a value between -999.999 and 9999.999 (ASCII)
• ‘<EOT>’ is ASCII 04 Hex
Command 59 Hex (89 Dec): Write DT position data (DT1-5).
Data format: <SOH><c:dddd.d><EOT
• Variable length record with two (2) data fields

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DDA Interface Manual
• The first data field contains one (1) character that controls which ‘DT
position’ memory location is written to (i.e. DT position #1, 2, 3, 4
or 5)
• This control character is limited to a value between 1 and 5 (ASCII)
• The second data field contains the ‘DT position’ data value to be
written to the respective ‘DT position’ memory location. This is a
variable length data field with one (1) to four (4) characters to the
left of the decimal character and fixed at one (1) character to the
right of the decimal character. The DT position data is limited to a
value between 0.0 and 9999.9 (ASCII)
• ‘<EOT>’ is ASCII 04 Hex
Command 5A Hex (90 Dec): Write firmware control code #1
Data format: <SOH><d:d:d:d:d:d><EOT>
• Fixed length record with one character in each data field
• ‘<SOH>’ is ASCII 01 Hex
• The first data field is the control variable for the data error detection
(DED) function. This variable can have a value of 0, 1, or 2. A value
of 0 enables the DED function, using a 16-bit checksum calculation.
A value of 1 enables the DED function, using a 16-bit CRC calcula-
tion. A value of 2 disables the DED function
• The second field is the control variable for the communication
time-out timer (CTT) function. This variable can have a value of 0 or
1. A value of 0 enables the CTT function, and a value of 1 disables
the CTT function
• The third data field is the control variable for temperature data
units This variable can have a value of 0 or 1. A value of 0 enables
Fahrenheit temperature units. A value of 1 enables Celsius tempera-
ture units
• The fourth data field is the control variable for linearization control.
This variable can have a value of 0 or 1. A value of 0 disables
linearization of the level data. A value of 1 enables linearization
• The fifth data field is the control variable for innage/ullage level
output. This variable can have a value of 0,1 or 2. A value of 0
enables normal innage level output. A value of 1 enables ullage level
output and a value of 2 enables ullage level output with reversed
DT submersion processing. Mode 2 is used for inverted transmitter
applications where the transmitter is installed from the bottom of the
tank
• The sixth data field is reserved for future use. The data value for this
field must be ‘0’ (ASCII 30 Hex)
• ‘<EOT>’ is ASCII 04 Hex
Command 5B Hex (91 Dec): Write hardware control code #1
Data format: <SOH><dddddd><EOT>
• Fixed length record with six (6) characters
• ‘<SOH>’ is ASCII 01 Hex
• The hardware control code controls various functions in the DDA
electronic hardware
• The hardware control code must match the hardware control code
stamped on the transmitter label. The control code on the label is
preceded by ‘CC’ (i.e. CC001122)
• ‘<EOT>’ is ASCII 04 Hex
Command 5C Hex (92 Dec): Not Defined
Command 5D Hex (93 Dec): Reserved for factory use
Command 5F Hex - 7F Hex - Reserved for future use
12.7 Diagnostic/Special command set
enum alarmStatusBits
INTERFACE_ALARM_HIGH = 0x0001
INTERFACE_ALARM_LOW = 0x0002
PRODUCT_ALARM_HIGH = 0x0004
PRODUCT_ALARM_LOW = 0x0008
ROOF_ALARM_HIGH = 0x0010
ROOF_ALARM_LOW = 0x0020
AVG_TEMP_ALARM_HIGH = 0x0040
AVG_TEMP_ALARM_LOW = 0x0080
MAGNET_IS_MISSING = 0x0100
DIG_TEMP0_ERROR = 0x0200
DIG_TEMP1_ERROR = 0x0400
DIG_TEMP2_ERROR = 0x0800
DIG_TEMP3_ERROR = 0x1000
DIG_TEMP7_ERROR = 0x2000
DIG_AVG_TEMP_ERROR = 0x4000
DELIVERY_IN_PROGRESS = 0x8000
TRIGGER_LEVEL_ERROR = 0x10000
EEPROM_ERROR = 0x20000
12.8 DDA Error codes
All error codes are preceded by a capital letter ‘E’ ASCII (45 hex) and are
in the form of ‘Exxx’ where ‘xxx’ can be any number from ‘000’ to ‘999’.
Error codes can be embedded in any data field within a transmitted
record. Certain DDA commands can generate multiple error codes. Refer
to the following examples:
Command 0A Hex:
<STX><Exxx><ETX><ccccc>
Command 2D Hex:
<STX><Exxx:Exxx:ddd.dd><ETX><ccccc>
Command 1E Hex:
<STX><E203:dddd.dd:dddd.dd:E207:dddd.dd><ETX><ccccc>
E102: Missing Float(s) (Level 1 or Level 2)
The number of floats measured by the hardware is less than the ‘number
of floats’ control variable
E201: No DTs Programmed
A request for temperature data has been made with the ‘number of DTs’
control variable set to equal zero (0) or all programmed DTs are set
inactive (for example, DT position data is set equal to zero (0.000))
E212: DT Communication Error
The indicated DT is not active (for example, DT position data is set equal
to zero (0) or is not responding)

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DDA Interface Manual
13. Dashboard, setup software
Adjustments to the calibration and set up parameters of the transmitter
can be performed using the Dashboard package. The software can be run
from any PC using a RS-485 to RS-232 converter.
Note:
You must use a RS-485 converter with ‘Send Data Control’ when
using the Dashboard to ensure proper operation.
13.1 Installing Dashboard
Adjustments to the setup and calibration of the DDA Interface can be
performed using the Dashboard. The Dashboard can be run from any
Windows 7 or newer OS using a RS485 to USB converter.
Perform the following steps to install the Dashboard and establish
communication:
1. Install Dashboard from the USB stick that came with the level
transmitter or go to factory website to download the
latest version.
2. Connect level transmitter to RS485 to USB converter, connect
24 Vdc power to the level transmitter, and connect the RS485 to
USB converter to the PC. Example setup shown below.
Fig. 5: Example setup
3. Open Dashboard and select DDA protocol from drop down
menu.
4. Select COM Port. Software will show active COM ports. Make sure
converter is connected before starting Dashboard or COM port
will not show.
5. The default address for the level transmitters from the factory is
192. Select address 192. If you do not know the address you can
use the Search function at the bottom of the address range or the
display menu.
Fig. 6: Initial screen
13.2 Home screen
Fig. 7: Home screen
The Dashboard Home Screen will look different based on whether or
not temperature has been ordered. If the level transmitter includes
temperature measurement then the Home Screen will look as shown. If
the level transmitter does not include temperature measurement then the
Home Screen will not show the bottom panel for temperature. The Home
Screen can be accessed by pressing the three white bars on the top left.
The level panel on top shows the level measurement for the Product

!!"
level and the graph is a time lapse of the graphical representation of the
numbers. The red line is the approximate maximum level based off of the
order length of the level transmitter. The numbers on the right of the level
panel are the Trigger Level for the Product Float on top and the Interface
Float on bottom. These are a representation of how strong of a return
signal the level transmitter is experiencing.
The temperature panel will only show if temperature measurement
was ordered and turned on. The left side shows the numerical value of
the average temperature of all temperature sensors below the product
level. The bar graph in the middle of the panel shows each individual
temperature measurement point. Temperature 1 is always the lowest
temperature closest to the bottom of the pipe or hose.

20
DDA Interface Manual
13.2 Home screen (Cont.)
Across the bottom of the Home Screen is the visual indication of the fault
codes from section 7. Green indicates no fault and red indicates fault.
$%!!

Fig. 8: Configuration
"!

Factory Set:
Auto Threshold: Default setting is ON and should not be turned off.
This feature allows the unit to automatically adjust the threshold for
optimal performance.
Product Float: Default setting of ON for all applications.
Interface Float: Default setting of ON if ordering 2 Loops. Default
&'*

the level transmitter will go into Fault.
Serial Number: Serial Number assigned by factory at the time of
manufacture. The serial number is used for tracking and replacement
parts. Do not change.
Temperature: Default setting of OFF if ordered without temperature.
Default setting of ON if ordered with temperature. Turning temperature
ON when the level transmitter was not ordered with temperature will
not cause temperature to work and will force the level transmitter into
Fault.
Display Enable: Default setting of ON. Display can be turned off by
changing to OFF and cycling power.

Reverse Measure: Allows the end user to change the direction in
which the level transmitter counts. The default setting is OFF and the
level transmitter will reference the tip of the pipe/hose and count up
from the tip. The ON setting will reference the head of the level trans-
mitter and count up as it moves towards the tip.
Device Address: "++;
Default address is 192. The default address should not be used in a
network.
13.4 Signal settings
Fig.9: Signal settings
Factory Set:
Gradient: Is the speed at which the magnetostrictive signals travel
along the sensing element. Typical range is from 8.9 to 9.2. Do not
change unless replacing the sensing element. Changing this number
will directly affect accuracy.
Signal Gain: Is the strength of the interrogation pulse. Factory uses
the same electronics for all lengths and adjusts the signal based on the
order length. Do not change unless instructed to do so by the Factory.
13.5 Level settings
Fig. 10: Level settings