Sutron ACCUBAR 5600-0120-2 Manual

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SUTRON ACCUBAR® BAROMETRIC PRESSURE
MULTIPLE INTERFACE SENSOR
OPERATIONS & MAINTENANCE
MANUAL
MODEL 5600-0120-1,-2
PART NO. 8800-1036
REVISION F

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Table of Contents
1. Introduction....................................................................................................................... 3
2. Quick Start ....................................................................................................................... 4
3. Cabling ............................................................................................................................. 5
Sutron-Supplied Cable.............................................................................................................. 5
Terminal Strip .......................................................................................................................... 5
SDI-12 Wiring .......................................................................................................................... 6
RS-232 Wiring ......................................................................................................................... 6
Analog Wiring .......................................................................................................................... 7
4. Setup and Operation ........................................................................................................ 8
Introduction .............................................................................................................................. 8
Nomenclature ........................................................................................................................... 8
Setting the Address ................................................................................................................... 8
Using Switches to Set the Address ............................................................................. 9
Using a command to Set the Address ......................................................................... 9
Verifying the Address and Operation ....................................................................................... 10
Commands (Overview) ............................................................................................................. 11
Making a Measurement ............................................................................................................ 12
Selecting a measurement command class ................................................................... 12
Always supported ......................................................................................... 12
Multiple long measurement time sensors ..................................................... 12
Improved data integrity checking ................................................................. 12
Making a non-concurrent Measurement (M command) ............................................. 12
Making a Concurrent Measurement (C command) .................................................... 14
Making a non-concurrent Measurement with CRC-16 (MC command)..................... 15
Making a Concurrent Measurement with CRC-16 (CC command) ............................ 16
Other Measurements .................................................................................................. 18
Changing the Units ..................................................................................................... 18
Setting User Units ...................................................................................................... 19
Setting Station Elevation ............................................................................................ 19
Analog Output Range ................................................................................................. 20
Converting Voltage to Pressure .................................................................................. 21
Configuring the Operating Mode and Averaging Time ............................................................ 22
Setting the Operating Mode ....................................................................................... 22
Setting the Averaging Time........................................................................................ 22
Resetting the unit to Factory Default Configuration ................................................................. 23
5. Command Reference ....................................................................................................... 24
Accubar Basic SDI-12 Commands ........................................................................................... 24
Accubar Extended Commands ................................................................................................. 33
Additional commands for Analog output units (-2) .................................................................. 36
6. Installation ........................................................................................................................ 37
7. Calibration ........................................................................................................................ 38
Factory Calibration ................................................................................................................... 38
Metrology Lab Calibration ....................................................................................................... 38
8. Troubleshooting and Maintenance ................................................................................... 40

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Troubleshooting ....................................................................................................................... 40
Additional Troubleshooting commands ..................................................................... 40
Measure Break detect time ........................................................................... 40
Test Analog output ....................................................................................... 41
Maintenance ............................................................................................................................. 41
9. Specifications for 5600-0120 Barometric ACCUBAR® ..................................................... 42
Appendix A -- Introduction to Pressure Measurement ............................................................. 44
Appendix B– Sutron Customer Service Policy ......................................................................... 48
Appendix C– Commercial Warranty ......................................................................................... 49
SUTRON MANUFACTURED EQUIPMENT ........................................................................ 49
NON-SUTRON MANUFACTURED EQUIPMENT .............................................................. 49
REPAIR AND RETURN POLICY .......................................................................................... 49
EXTENDED WARRANTY AND ON-SITE MAINTENANCE ............................................. 49

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1. Introduction
The 5600-0120 ACCUBAR® Pressure Sensor is a solid-state pressure transducer suitable for data collection and
monitoring applications. The ACCUBAR® sensor has been designed with the following features to operate in a wide
range of applications:
low power
consumption (-1)
standby power is 0.2mA, average power when taking measurements every
15 minutes via SDI-12 is less than 0.25 mA.
high accuracy
0.5 mB (hPa)
full temperature
compensation
the accuracy is maintained over the temperature range of -40 to +60C.
selectable units
the sensor can be configured to output the data in mB, hPa, kPa, "Hg,
mmHg, Atm, and psi.
non-volatile
setup
the setup is stored in EEROM and remains even when power is removed
from the sensor
wide operating
voltage
the sensor operates over the voltage range of 8 to 28 VDC

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2. Quick Start
The ACCUBAR® sensor comes with a cable and setup compatible with a Sutron 8200. If you have an
8200, you are able to operate the ACCUBAR® without making any changes to the wiring or setup. If you
do not have an 8200, you will need to change the wiring to make it connect to your system as described in
Chapter 3.
To use the ACCUBAR® with the 8200 follow these simple steps:
 Connect the sensor to your Sutron 8200 Data Logger SDI-12 port on the front panel of the 8200, using
the factory supplied cable.
 Use the 8200 SYSTEM SETUP\ENABLE SENSOR menu to turn SDI0-1 ON. If you want to see the
units indicator for the measurement also turn SDI0-2 ON. Refer to the Sutron 8200 Data Logger
Operations and Maintenance Manual if you do not know how to ENABLE sensors.
 Use the 8200 VIEW\LIVE READINGS menu and select the SDI0-1 sensor.
The 8200 will now display the pressure readings from the ACCUBAR® sensor in units of milliBars (mB) and
hectoPascals (hPa). Note: These two units of measure are equivalent.

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3. Cabling
Sutron-Supplied Cable
The ACCUBAR® comes with a cable pre-wired to an internal terminal strip which has a DB9M connector
on it. This cable will plug into a Sutron 8200. The wiring of the cable is as follows. Note the two different
possibilities for the colors of the conductors.
Name
Terminal
Color Opt 1
Color Opt 2
DB9M Pin
Ground
1
Blue
Yellow
5
RxD
2
Yellow
Red
3
TxD
3
Orange
Brown
2
Battery
4
Black
Gray
9
Ground
5
Gray
Blue
7
SDI Data
6
Red
Black
1
DTR
7
Green
Orange
4
Analog Out +
8
Purple
Green
6
Analog Out 
9
White
Violet
8
Analog output is only available on -2 versions of the ACCUBAR®.
Terminal Strip
The ACCUBAR® has a terminal strip to which you can connect a cable to interface to the sensor. To access
the terminal strip, use a screwdriver and remove the cover of the sensor. The terminal strip is located on the
PCB. The terminal strip has 9 connections which are as follows:
Name
Terminal
Unit Type
Ground
1
-1 and -2
RxD
2
-1 and -2
TxD
3
-1 and -2
Battery (8 to 28 volts)
4
-1 and -2
Ground
5
-1 and -2
SDI Data
6
-1 and -2
DTR
7
-1 and -2
Analog Out +
8
-2 only
Analog Out 
9
-2 only
Terminal connection 1 is labeled with a 1 on the printed circuit board next to the terminal strip. The analog
output is only available on the -2 unit.

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SDI-12 Wiring
The SDI interface conforms to SDI-12 standard version 1.0 through 1.3. Only three wires are needed to use
the ACCUBAR® SDI-12 interface. The following table contains pin descriptions for the J5 terminal block
inside the ACCUBAR®:
Description
J5 Terminal
Data Recorder Connection
Battery
4
Connect to Battery or data recorder supplied
voltage
Ground
5
Connect to Ground
SDI Data
6
Connect to data recorder SDI Data line
RS-232 Wiring
The default communications parameters for RS-232 are:
 1200 baud
 7 data bits with even parity added as an eighth bit
 One stop bit
The following table contains pin descriptions for the J5 terminal block inside the ACCUBAR®, with the
corresponding RS-232 cable connections to PC.
Description
J5
Terminal
IBM AT Connection
(DB-9F cable)
IBM PC or any DTE
Connection (DB-25-F
cable)
Ground
1
5
7
Receive Data
2
3
2
Transmit Data
3
2
3
Battery
4
Supply Voltage
Supply Voltage
Ground
5
Supply Ground
Supply Ground
SDI Data
6
DTR
7
4
20
When Data Terminal Ready (DTR) is off, the ACCUBAR® enters a low-power standby mode and the RS-
232 drivers are turned off. When DTR is raised, the unit resumes normal operation.
NOTE: The unit can be powered off of the DTR pin but a typical RS-232 connector will not supply enough
current to power the unit and an external supply will be required. Supply Voltage and Supply Ground are
where the supply voltage for the ACCUBAR® is applied, if necessary.
Even though the unit can be powered off of the DTR pin, the DTR and Battery pins (4 and 7) are NOT
interchangeable. The DTR line must be high for the ACCUBAR® to acknowledge an RS-232 connection.
Pins 1 and 5 are connected internally and are interchangeable. The two connections are provided as a
convenience to the RS-232 user.

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Analog Wiring
The analog output is a 0 to 5V output with setable range. The following table contains pin descriptions
for the J5 terminal block inside the ACCUBAR®.
Description
J5 terminal
Connection
Battery
4
Connect to Battery + or data recorder supplied voltage
Ground
5
Connect to Battery - or data recorder ground
Analog out +
8
Connect to Analog + input
Analog out -
9
Connect to Analog - input
NOTE: Analog out - is connected internally to ground. The analog out - pin is provided to allow the unit
to be connected to a differential input and eliminate errors due to the voltage drop in the ground connection
on long cable runs.

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4. Setup and Operation
Introduction
This section will familiarize you with the steps and commands needed to alter the setup of the ACCUBAR®.
If you will use the ACCUBAR® sensor at address 0 (the factory default) and can accept the output in units
of mB (hPa), you will not need to use these commands. Typically, you will need to issue some of the
commands, so we recommend you learn how to do so. Learning to issue commands also helps if you need
to troubleshoot a sensor.
Users of the analog version (5600-0120-2) of the ACCUBAR® will not need to use these commands if the
output range of 600 to 1100 mB is acceptable. Users of the analog version will, however, probably wish to
customize the output range to suit their application. To customize the output range, analog users will need
to know how to issue commands.
To issue commands to the ACCUBAR® via SDI-12, you will need to connect it to a data recorder, such as a
Sutron 8210, 8310, 9210, or Xpert which is capable of issuing standard and extended SDI-12 commands.
Follow the instructions in Sections 2 and 3 in order to make these connections.
To issue commands to the ACCUBAR® via RS-232, you will need to connect it to an RS-232 terminal or to
a computer running terminal emulation (communications) software. Follow the instructions in Section 3 in
order to make these connections
Nomenclature
All commands have three components: the device address, the command body, and the command
termination.
The device address is a single character and is the first character of a command. In the examples that
follow, it is usually the number 0 (the default address as shipped from the factory).
The command body and the responses are shown as a combination of upper and lower case letters. The
upper case letters are the fixed portions of the command and the lower case letters are the variables or
values. In the specific examples, you will see that the lower case letters are replaced with actual numbers.
All commands are shown with an exclamation point (!) as the command terminator. This command
terminator works with both the SDI-12 and RS-232 interfaces. With RS-232, you have the additional
option of terminating the command with a carriage return <CR> and/or line feed <LF> in place of the
exclamation point.
Setting the Address
If you are using the ACCUBAR® connected with other SDI-12 devices, you will need to change the
ACCUBAR® address. Otherwise, skip this section. The address simply lets multiple devices share the
same wiring. When the data recorder needs data from a particular sensor, it requests data using an address.
Only the device with the matching address will reply. For convenience in setting up the unit when only one
sensor is connected, the ACCUBAR® supports wildcard addresses of asterisk (*) and question mark (?).
The default address is 0. There are two ways to set the address: switches and command.

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Using Switches to Set the Address
NOTE: It is usually easier to set the address via a software command, as described in the next section.
Remove the cover for the sensor and set the switches to one of the settings as follows:
Address
Switch 4
Switch 3
Switch 2
Switch 1
0
off
Off
off
off
1
off
Off
off
ON
2
off
Off
ON
off
3
off
Off
ON
ON
4
off
ON
off
off
5
off
ON
off
ON
6
off
ON
ON
off
7
off
ON
ON
ON
8
ON
Off
off
off
9
ON
Off
off
ON
A
ON
Off
ON
off
B
ON
Off
ON
ON
C
ON
ON
off
off
D
ON
ON
off
ON
E
ON
ON
ON
off
F
ON
ON
ON
ON
Note: all other switches in the ACCUBAR® need to be OFF. The factory default for all switches is OFF
(address 0). The ACCUBAR® will not operate properly if any of the switches (5 to 8) are set ON.
Using a command to Set the Address
In order to set the address by SDI-12 command or RS-232 command, the DIP switch address must be set to
0 (Switches 1,2,3,4 OFF). This is the factory setting for the switches. Also, no other SDI-12 devices
connected to the system should be set to address 0 or to the desired ACCUBAR® address. Hint: if you do
not know the address of a particular ACCUBAR®, use the unknown address command to have the
ACCUBAR® identify itself.
NOTE: There can only be one ACCUBAR® connected in order for the unknown address command to
work. The syntax for the unknown address command is
*X?!
The ACCUBAR® also supports an alternate version of the unknown address command which is a command
acknowledge to a wildcard address. The syntax for this version is:
*!
Beginning with version 1.2 of the SDI-12 specification there is an address query command defined.
Therefore another version of the request unknown address or address query command is:
?!
The SDI-12 command for setting the ACCUBAR®'s address is the XAD command

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0XADnAn!
where a is the current address of the device, n is the new SDI-12 address
and n is the same address repeated (0 to 9, :;<=>?,A to Z,a to z).
Note that the command follows the SDI-12 standard beginning with the address and ending with "!".
The ACCUBAR® will issue a reply message in response to the command if the command was recognized.
The message will be 00011 which is explained in the Command Reference. If you do not get this message,
try the command again and check the switches (Unit must be set to address 0 since that is the address this
command trying to change from). Note: The ACCUBAR® will not respond if the command is invalid, i.e.,
there is a typing mistake in the command or the two copies of the new address do not match.
As an example, the following command would set the ACCUBAR® address to 5:
0XAD5A5!
Subsequently, the address can be set to a different address, 9 for example, by the command:
5XAD9A9!
The ACCUBAR® also supports an alternate version of the set Address command as specified in SDI-12
standard version 1.2.
0An!
where 0 is the current address of the device, n is the new SDI-12 address
(0 to 9, A to Z, a to z).
As an example, the following command would set the ACCUBAR® address to 5:
0A5!
The ACCUBAR® will respond with the new address which is 5.
Subsequently, the address can be set to a different address, 9 for example, by the command:
5A9!
Verifying the Address and Operation
The ACCUBAR® will respond with an identifying message when it receives the send identification
command, I. The format of the command is:
aI!
Where a is the address for the ACCUBAR®.
The ACCUBAR® will reply with

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a13 SUTRON 0120-11.0sssssssVvvv
a
13
SUTRON
0120-1
1.0
sssssss
Vvvv
Where:
SDI-12 address
supports SDI version 1.3 commands
manufacturer SUTRON
Sutron model number
hardware revision level
sensor serial number
the software revision
If you do not get a reply, check the address setting for the ACCUBAR® and make sure you use the proper address for
the sensor.
Commands (Overview)
The commands to set up and operate the ACCUBAR® are those defined by the SDI specifications 1.0 plus
some extended commands defined by Sutron. All commands start with a single-character address and end
in an exclamation point. The address is a single character with values 0 to 9, :;<=> ?, A to Z, and a to z.
Values are entered in the form of a polarity (+ or -) sign followed by up to seven digits, including a decimal
point. The commands are in ASCII and all the replies use printable ASCII characters followed by <CR>
<LF>.
The ACCUBAR® replies to all SDI commands it supports. If the ACCUBAR® receives a command it does
not support, no reply is made. The reply will have one of two forms:
a0000
where a is the address and the 0000 indicates that there is no
further message to send
or
atttn
and
a
where a is the address, ttt is the amount of time, in seconds,
the ACCUBAR® needs to make the measurement or process
the command and n is the number of values that can be
collected. In this form the sensor will also respond with its
address when the data is ready to collect. This response is
called a service request.
If you issued the change address command or the identify command described in the previous sections, you
already have some experience with using ACCUBAR® commands. There are other commands available to
make measurements, set the type of output units for the measurements, perform special scaling of the
measurements, etc. The following sections describe the commands by function.

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Making a Measurement
There are four classes of measurement commands which will be referred to as M commands (Measurement
Commands), C commands (Concurrent Measurement Commands), MC commands (Measurement
commands with CRC-16), and CC commands (Concurrent Measurement Commands with CRC-16).
Concurrent measurement commands are new to version 1.2 of the SDI-12 specification. The commands
with CRC-16 are new to version 1.3 of the SDI-12 specification. In the original class of “M” measurement
commands, the data recorder issued the measurement command and then waited for the sensor to complete
the measurement before continuing the data collection cycle. Only one sensor could be accessed at a time
and a maximum of nine parameters could be returned. With version 1.2 of the specification, concurrent
measurements were defined. With a concurrent measurement, the data recorder can request the sensor to
take a measurement, determine how long it will be until the sensor has a reading, and then continue on
making requests to other sensors on the SDI-12 bus. This way multiple sensors are taking measurements
concurrent with each other. Once the measurement time for a sensor has expired the data recorder polls the
sensor for the data. The CRC-16 commands that were added in version 1.3 of the specification add a 16 bit
cyclic redundancy check (CRC-16) to the returned data values. This provides an additional means for the
data recorder to ensure that the collected data has not been corrupted. Software support for SDI-12 version
1.3 was added in software revision V2.0. Version V1.9 and before only support the M commands.
Selecting a measurement command class
Always supported
The first requirement is that the data recorder support the command. All SDI-12 data recorders support the
non-concurrent measurement M command. With the M command the data recorder collects data from the
sensors one at a time.
Multiple long measurement time sensors
When collecting data from several SDI-12 sensors that have long measurement times, the complete data
collection cycle can be shortened by utilizing concurrent commands. The data recorder can initiate the
measurement on all the sensors and when each finishes, then collect the data from all of them. Since the
measurement times overlap, the complete data collection cycle is shorter. There is no advantage to the
concurrent measurement C command when there is only one sensor.
Improved data integrity checking
The measurement command classes with CRC-16 (MC and CC) offer additional data integrity checking
over the non CRC-16 commands (M and C). The non CRC-16 commands offer data integrity checking in
the form of parity and the SDI-12 command structure. The CRC-16 commands offer some additional data
integrity through the addition of a CRC-16. Since the CRC-16 commands are brand new in SDI-12 version
1.3, not as many data recorders support them. In most applications, lack of this support on the part of the
data recorder will not be missed since non CRC-16 SDI-12 commands still offer significant data integrity
checking. If the data recorder supports CRC-16 commands, then it is recommended to use them when
collecting data from this sensor in order to benefit from the increased noise immunity.
Making a non-concurrent Measurement (M command)
The command to tell the ACCUBAR® to make a measurement with the original measurement command is:
aM!
where a is the address character, and M is the command to
make a measurement

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Most data recorders will issue this command and automatically handle the reply to collect data. You can
also issue the command yourself. In reply, the ACCUBAR® will respond with
attt2
acknowledging it is address a and indicating that after ttt
seconds are allowed for the measurement, 2 values can be
collected.
When the measurement is complete, the ACCUBAR® responds with a service request
A
where a is the address character
Note that you still don't have any data from the ACCUBAR®. To request the data after a measurement,
aD0!
where a is the address character and D0 is the command to
retrieve measured data. (Note: 0 is zero, not the letter O)
In this case the ACCUBAR® will reply with two values in the format:
avu
where a is the address, v is the data value and u indicates the
units. Both v and u have the format of a polarity (+ or -) sign
followed by up to seven digits, including a decimal point. One
example of a response would be
0+1013.25+0
The u indicates the units of the measurement. When u is 0, the value has units of mB(hPa). When u is 1,
the units are inches of mercury ("Hg). When u is 9, the units depend on a user entered slope and offset. u
can also take on additional values if a station elevation offset has been entered The following table
summarizes all the values of u.
0 units are mB (hPa)
1 units are "Hg
2 units are kPa
3 units are mmHg
4 units are Atm
5 units are psia
9 units depend on user-entered scale and offset.
If the station elevation offset is non-zero, then one of the
following values of u will be returned:
10 units are mB + station elevation offset
11 units are "Hg + station elevation offset
12 units are kPa + station elevation offset
13 units are mmHg + station elevation offset
14 units are Atm + station elevation offset
15 units are psia + station elevation offset
19 user units with non-zero station elevation offset
(mB + elevation offset)  user scale + user offset
set by XE or XS Set by XUU

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In most cases, you will not set up the recorder to store this units identifier. It is provided in response to the
standard measure command to eliminate confusion as to the computation used to come up with the final
value.
Making a Concurrent Measurement (C command)
The command to tell an ACCUBAR® to make a concurrent measurement is:
aC!
where a is the address character, and C is the command to
make a concurrent measurement
The concurrent measurement command was first defined in version 1.2 of the SDI-12 specification.
Therefore the data recorder will have to be SDI-12 version 1.2 or higher compliant before it can be
expected to issue this command and automatically handle the reply to collect data. You can also issue the
command yourself. In reply, the sensor will respond with
attt02
Acknowledging it is address a and indicating that after ttt
seconds are allowed for the measurement, 2 values can be
collected.
When the measurement is complete, the sensor does NOT issue a service request Note: this is different
from the M command.
To request the data after a measurement,
aD0!
where a is the address character and D0 is the command to
retrieve measured data. Note: the number zero follows D,
not the letter O.
In this case, the ACCUBAR® will reply with two values in the format:
avu
where a is the address, v is the data value and u indicates the
units. Both v and u have the format of a polarity sign ( or )
followed by up to seven digits, including a decimal point.
The u indicates the units of the measurement. When u is 0, the value has units of mB(hPa). When u is 1,
the units are inches of mercury ("Hg). When u is 9, the units depend on a user entered slope and offset. u
can also take on additional values if a station elevation offset has been entered The following table
summarizes all the values of u.

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0 units are mB (hPa)
1 units are "Hg
2 units are kPa
3 units are mmHg
4 units are Atm
5 units are psia
9 units depend on user-entered scale and offset.
If the station elevation offset is non-zero, then one of the
following values of u will be returned:
10 units are mB + station elevation offset
11 units are "Hg + station elevation offset
12 units are kPa + station elevation offset
13 units are mmHg + station elevation offset
14 units are Atm + station elevation offset
15 units are psia + station elevation offset
19 user units with non-zero station elevation offset
(mB + elevation offset)  user scale + user offset
set by XE or XS Set by XUU
In most cases, you will not set up the recorder to store this units identifier. It is provided in response to the
standard measure command to eliminate confusion as to the computation used to come up with the final
value.
Making a non-concurrent Measurement with CRC-16 (MC command)
The command to tell the ACCUBAR® to make a non-concurrent measurement with a CRC-16 check on the
data is:
aMC!
where a is the address character, and MC is the command to
make a non-concurrent measurement with a CRC-16
The non-concurrent measurement with CRC-16 command was first defined in version 1.3 of the SDI-12
specification. Therefore the data recorder will have to be SDI-12 version 1.3 or higher compliant before it
can be expected to issue this command and automatically handle the reply to collect data. You can also
issue the command yourself. In reply, the ACCUBAR® will respond with
attt2
acknowledging it is address a and indicating that after ttt
seconds are allowed for the measurement, 2 values can be
collected.
When the measurement is complete, the sensor responds with a service request
a
where a is the address character
Note that you still do not have any data from the ACCUBAR®. To request the data after a measurement,
aD0!
where a is the address character and D0 is the command to
retrieve measured data. Note: the number zero follows D,
not the letter O.

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In this case, the sensor will reply with two values in the format:
avuC
where a is the address, v is the data value, u indicates the units,
and C is the CRC-16 encoded into 3 ASCII characters. Both v
and u have the format of a polarity sign ( or ) followed by up
to seven digits, including a decimal point. The CRC-16 is
always the last three characters which are never a numeric digit.
The u indicates the units of the measurement. When u is 0, the value has units of mB(hPa). When u is 1,
the units are inches of mercury ("Hg). When u is 9, the units depend on a user entered slope and offset. u
can also take on additional values if a station elevation offset has been entered The following table
summarizes all the values of u.
0 units are mB (hPa)
1 units are "Hg
2 units are kPa
3 units are mmHg
4 units are Atm
5 units are psia
9 units depend on user-entered scale and offset.
If the station elevation offset is non-zero, then one of the
following values of u will be returned:
10 units are mB + station elevation offset
11 units are "Hg + station elevation offset
12 units are kPa + station elevation offset
13 units are mmHg + station elevation offset
14 units are Atm + station elevation offset
15 units are psia + station elevation offset
19 user units with non-zero station elevation offset
(mB + elevation offset)  user scale + user offset
set by XE or XS Set by XUU
In most cases, you will not set up the recorder to store this units identifier. It is provided in response to the
standard measure command to eliminate confusion as to the computation used to come up with the final
value.
Making a Concurrent Measurement with CRC-16 (CC command)
The command to tell the ACCUBAR® to make a concurrent measurement with CRC-16 check on the data
is:
aCC!
where a is the address character, and CC is the command to
make a concurrent measurement with a CRC-16 check on the
returned data
The concurrent measurement with CRC-16 command was first defined in version 1.3 of the SDI-12
specification. Therefore the data recorder will have to be SDI-12 version 1.3 or higher compliant before it
can be expected to issue this command and automatically handle the reply to collect data. You can also
issue the command yourself. In reply, the ACCUBAR® will respond with

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attt02
acknowledging it is address a and indicating that after ttt
seconds are allowed for the measurement, 2 values can be
collected.
When the measurement is complete, the sensor does NOT issue a service request Note: this is different
from the M and MC commands.
To request the data after a measurement,
aD0!
where a is the address character and D0 is the command to
retrieve measured data. Note: the number zero follows D,
not the letter O.
In this case, the sensor will reply with two values in the format:
avuC
where a is the address, v is the data value, u indicates the units
the value is expressed in, and C is the CRC-16 encoded into 3
ASCII characters. Both v and u have the format of a polarity
sign ( or ) followed by up to seven digits, including a decimal
point. The CRC-16 is always the last three characters which are
never a numeric digit.
The u indicates the units of the measurement. When u is 0, the value has units of mB(hPa). When u is 1,
the units are inches of mercury ("Hg). When u is 9, the units depend on a user entered slope and offset. u
can also take on additional values if a station elevation offset has been entered The following table
summarizes all the values of u.
0 units are mB (hPa)
1 units are "Hg
2 units are kPa
3 units are mmHg
4 units are Atm
5 units are psia
9 units depend on user-entered scale and offset.
If the station elevation offset is non-zero, then one of the
following values of u will be returned:
10 units are mB + station elevation offset
11 units are "Hg + station elevation offset
12 units are kPa + station elevation offset
13 units are mmHg + station elevation offset
14 units are Atm + station elevation offset
15 units are psia + station elevation offset
19 user units with non-zero station elevation offset
(mB + elevation offset)  user scale + user offset
set by XE or XS Set by XUU
In most cases, you will not set up the recorder to store this units identifier. It is provided in response to the
standard measure command to eliminate confusion as to the computation used to come up with the final
value.

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Other Measurements
The SDI-12 standard allows for other measurement commands such as M1, M2 etc., other current
measurement commands such as C1, C2, etc., other non-concurrent measurements with CRC-16 such as
MC1, MC2, etc, and other concurrent measurement with CRC-16 such as CC1, CC2, etc. This unit
maintains symmetry across all four classes of commands, that is, it returns the same information to a C1 as
it does to a M1 or a MC1 or a CC1. The ACCUBAR® supports the following optional measurement
commands:
aM1!
aC1!
aMC1!
aCC1!
measure mB (hPa) using factory calibration. Do not apply any
user scaling, station elevation or offsets. This returns 1 value
and the units are fixed to mB (hPa).
aM2!
aC2!
aMC2!
aCC2!
measure temperature (Celsuis or Farenheit). This returns two
values: the temperature and the units. The units will be 0 for
Celsius and 1 for Farenheit.
aM3!
aC3!
aMC3!
aCC3!
measure user scale, user offset, elevation offset. Use this if
you want to view the user-entered values that can affect the
value returned by the M command.
aM4!
aC4!
aMC4!
aCC4!
measure calibration lab scale and offset. Use this if you want
to view the calibration lab values that can affect the value
returned by the M, C, MC, and CC commands.
(Version 2.0
and higher.)
aM6!
aC6!
aMC6!
aCC6!
Measure temperature and pressure. The output is the
concatenation of the M2 and M commands. Temperature,
temperature units, Pressure, Pressure units.
(Version 2.0
and higher.)
aM7!
aC7!
aMC7!
aCC7!
Measure mB and degrees C using factory calibration. Do not
apply any user scaling, field calibration or offsets. This
returns two values and the units are fixed to mB and degrees
C.
Remember to issue the aD0! command after the measurement is complete in order to retrieve the data.
Changing the Units
As noted above, the aM! command can return the pressure in several different units. The selection of the
units is made using the XUPcommand:

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aXUP+n+d!
where n is one of the selections from the following table and d
is the number of digits to the right of the decimal point.
N
Type Units
Comments
0
mB (hPa)
1
inches of
mercury
2
kPa
3
mmHg
4
Atm
5
psia
9
user units
the value has units that depend on the
values entered using the XUU command.
For example, the command
aXUP+0+2!
will specify the output to be in the default units (mB) with a resolution of 2 decimal places. The second
parameter (2 in the example) is optional. If omitted, the resolution is not changed.
Setting User Units
If you want the sensor to read out in units other than the factory-programmed units, you will need to use the
XUP command to set the units to 9, user units. When user units are selected, the software will use the
equation:
output = mB * scale + offset
where scale and offset are values you can enter into the system.
The XUU command is used to enter the user scale and offset. The format of the command is:
aXUUso!
where s is the signed scale and o is the signed offset.
For example, the following command will set the scale to 70.32 and the offset to 0.0:
aXUU+70.32+0
Similarly, the slope and offset can be set to any values that will produce the desired units.
NOTE: Remember that both a XUU and a XUP command are required for the ACCUBAR®to
report in user-defined units.
Setting Station Elevation
The ACCUBAR® will usually be installed at an elevation other than sea level. To have the ACCUBAR®
report the atmospheric pressure at sea level, the sensor's elevation offset from sea level must be entered.
The ACCUBAR® has two commands that can be used to enter this elevation offset. The XE command
allows direct setting of an elevation offset which will be added to the measurement to compute atmospheric
pressure at sea level: