Sutron AnalogPlus SDI-12 6661-1248-1 Manual

SDI-12 ANALOG PLUS
MODEL6661-1248-1
OPERATIONS&
MAINTENANCEMANUAL
Part No. 8800-1145
Revision - D
15-Oct-2010
Sutron Corporation
22400 Davis Drive
Sterling, Virginia 20164
TEL: [phone]
http://www.sutron.com/

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Table of Contents
1. Introduction..........................................................................................................................1
Features....................................................................................................................................1
2. Quick Start............................................................................................................................2
3. SDI-12 Commands (Overview) ...........................................................................................4
Setting the Address...................................................................................................................4
Verifying the Address and Operation.......................................................................................5
Making a Measurement............................................................................................................6
Selecting a measurement command class...................................................................6
Always supported ........................................................................................6
Multiple long measurement time sensors.....................................................6
Improved data integrity checking ................................................................6
Example: (M command) ............................................................................................6
C, MC and CC commands..........................................................................................7
Other Measurements ..................................................................................................7
Factory Programmed Default Measurements ...........................................................................7
M, C, MC, CC .............................................................................................7
M1, C1, MC1, CC1 .....................................................................................8
M2, C2, MC2, CC2 .....................................................................................8
M3, C3, MC3, CC3 .....................................................................................8
M4, C4, MC4, CC4 .....................................................................................8
M5, C5, MC5, CC5 .....................................................................................8
M6, C6, MC6, CC6 .....................................................................................8
M7, C7, MC7, CC7 .....................................................................................8
M8, C8, MC8, CC8 .....................................................................................8
M9, C9, MC9, CC9 .....................................................................................8
4. Measurements......................................................................................................................9
Setting a Measurement (Quick Set-up With Default Parameters) ............................................9
Voltage Measurement (Single-ended)........................................................................9
Voltage Measurement (Differential) ..........................................................................9
Ratiometric Measurement..........................................................................................9
Tipping-Bucket Measurement....................................................................................10
Counts Measurement..................................................................................................10
Frequency Measurement............................................................................................10
Period Measurement ..................................................................................................10
Quadrature Shaft Encoder Measurement ...................................................................11
Notes on Handar 436 Quadrature Ecoder (any switch closure output encoders) .......11
State of Port ...............................................................................................................12
Setting a Measurement (Specific Set-up With User-Defined Parameters) ...............................13
Voltage Measurement ................................................................................................13
SDI-12 set-up command..............................................................................13
Examples .....................................................................................................14
Verification and Reading current Set-up......................................................14
Ratiometric Measurement..........................................................................................15
SDI-12 set-up command..............................................................................15
Examples .....................................................................................................16
Verification and Reading current Set-up......................................................16
Tipping-Bucket Measurement....................................................................................17
SDI-12 set-up command.............................................................................17

ii
Examples .....................................................................................................17
Verification and Reading current Set-up......................................................18
Count Measurement...................................................................................................18
SDI-12 set-up command..............................................................................18
Examples .....................................................................................................18
Verification and Reading current Set-up......................................................19
Frequency Measurement............................................................................................19
SDI-12 set-up command.............................................................................19
Examples .....................................................................................................19
Verification and Reading current Set-up......................................................20
Period Measurement ..................................................................................................20
SDI-12 set-up command..............................................................................20
Examples .....................................................................................................20
Verification and Reading current Set-up......................................................21
Quadrature Shaft Encoder Measurement ...................................................................21
Offset...........................................................................................................22
Scale-Factor.................................................................................................22
Direction of Rotation...................................................................................22
Average, Minimum and Maximum Value/Measurement-time.....................23
Status Byte...................................................................................................23
Verification and Reading current Set-up......................................................23
State of Port ...............................................................................................................23
Example.......................................................................................................23
Switched Voltage SW‟D ..........................................................................................................24
Resetting to a Factory Default Configuration...........................................................................24
5. Measurement Configuration Recommendations.................................................................25
Analog measurement Parameters .............................................................................................25
Channel, Gain, Buffering...........................................................................................25
Averaging / Filtering..................................................................................................25
Vref warm-up time.....................................................................................................26
Switched voltage and Switched voltage warm-up time..............................................26
Example Setup Tutorials..........................................................................................................26
AT/RH Probe.............................................................................................................26
Continuously Powered.................................................................................26
Powered for measurements only..................................................................27
Air Temperature Sensor.............................................................................................27
4-20mA Output Sensor ..............................................................................................28
6. Troubleshooting and Maintenance......................................................................................29
Troubleshooting .......................................................................................................................29
Maintenance.............................................................................................................................29
7. Specifications for SDI-12 AnalogPlus module.....................................................................30
APPENDIX A -- Command Reference .....................................................................................31
APPENDIX B -- SDI-12 with the Sutron 8200, 8200A, and 8210.............................................37
Entering Extended Commands for Configuration Purposes.....................................................37
From the Front Panel..................................................................................................37
From a PC connected to the RS-232 port...................................................................37
Logging data from the M1 or M2 commands or from addresses above 9 ................................37
Logging data with multiple data recorders ...............................................................................38
Setup two Sutron data recorders with one SDI-12 AnalogPlus module.....................38
Setup two Sutron Data Recorders with two SDI-12 AnalogPlus modules.................38

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APPENDIX C -- Dimensions.....................................................................................................39
APPENDIX D -- Sutron Customer Service Policy.....................................................................40
APPENDIX E -- Commercial Warranty.....................................................................................41
SUTRON MANUFACTURED EQUIPMENT........................................................................41
NON-SUTRON MANUFACTURED EQUIPMENT..............................................................41
REPAIR AND RETURN POLICY..........................................................................................41
EXTENDED WARRANTY AND ON-SITE MAINTENANCE.............................................41

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1. Introduction
The SDI-12 AnalogPlus module has 5 ports to take measurements from vast variety of sensors and transfer
the results to a data recorder. Three of them (AN1, AN2, AN3) are exclusively for analog measurements, one
(DIN) is exclusively for digital measurements, and AN4 can be used for analog as well as logic level driven
digital measurements.
Features
High accuracy & excellent stability
Four Analog inputs with
oCan be configured for Single-ended or Differential voltage measurements
oReference voltage output for ratiometric sensors (bridges and potentiometers)
o24-bit A/D converter
o0-5V input range
oProgrammable gain (1 to 128) user specified or Automatic gain
oSimultaneous 50Hz and 60Hz noise rejection.
One digital input with selectable pull-up (or pull-down) to support switch closure type inputs.
Additional digital input for 0-5 V signals (shared with Analog channel 4).
Frequency measurement : 1 Hz to 8 kHz
Counts measurement
Quadrature Shaft Encoder measurement
Programmable switch de-bounce times to prevent multiple counts on a single event.
Programmable switched 5 volts and 12 volts output
Low power consumption : < 0.5 mA in standby mode
Programmable coefficients for conversion to engineering units such as degrees C.
Supports SDI-12 version 1.3
Configurable measurement commands.
Non-volatile setup
DIN rail mountable with a real spring on the metal clip
Pluggable terminal blocks

2
2. Quick Start
The SDI-12 AnalogPlus module arrives ready to use for many voltage measuring applications.
The module has four pluggable terminal blocks with three connections each. One block contains the SDI-12
connection to the SDI-12 Data Recorder (+12V power, Ground, and Data). The other three provide
connections for the sensors.
Left Side Top
Right Side Top
Label
Description
Label
Description
SW‟D
Switched Voltage out (+5 or +12)
Vref
Reference Voltage out (2.5V)
D IN
Digital input
GND
Ground
AN4
Analog input 4 / optional digital in
AN1
Analog input 1
Left Side Bottom (SDI-12 connection)
Right Side Bottom
Label
Description
Label
Description
+12
+12V SDI power from recorder
AN2
Analog input 2
GND
Ground connection to recorder
GND
Ground
DATA
SDI-12 data line to recorder
AN3
Analog input 3
The unit comes configured from the factory at SDI-12 address 0 and ready to make analog readings. Just
issue the basic SDI-12 start measurement command “M” to address 0 ( 0M! ) and the unit will initiate a
reading of all four analog inputs. Get the data back with a “D0” command ( 0D0! ) (done automatically by
most data recorders when they are measuring) and the unit will return the four voltage readings (AN1, AN2,
AN3, AN4).
If using with other SDI-12 sensors, then the unit will need to be set to a unique address. This is done with the
change address command ( aAb! ) where “a” is current address and “b” is the new address. The unit needs to
be only SDI-12 module on the bus at address “a” when this command is issued, or you will end up changing
both units to address “b”. For example, to change the address from the factory default of “0” to “2”, issue the
command: 0A2!
All future commands will then need to be sent to address 2.
To query a module as to its address, ensure that it is the only SDI-12 module on the bus and then issue the
address query command: ?!
The unit will respond with its address.
To confirm the SDI-12 communication with a module, the SDI-12 send identification command can be issued
(to address 0 in the example): 0I!
The unit will respond with its identification string. The string from the SDI-12 AnalogPlus module will look
similar to the following: 013 SUTRON 1248-11.0 A1.2
which shows a response from address 0, that the unit supports SDI-12 specification 1.3 (and therefore 1.2,
1.1, and 1.0), that the manufacturer is SUTRON, and that the model is a 1248-1.
Right Bottom
Right Top
Left Bottom
Left Top

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If you need more than a 0-5V single ended voltage reading, then refer to the measurements section of the
manual for further details on configuring the different measurement types.

4
3. SDI-12 Commands (Overview)
The commands to set up and operate the SDI-12 AnalogPlus module are those defined by the SDI-
12 specifications plus some extended commands defined by Sutron. The commands are in ASCII
and all the replies use printable ASCII characters followed by <CR> <LF>. The case of the letters is
important. An “A” is not the same as an “a”.
All commands have three components: the device address, the command body, and the command
termination.
The device address is a single character with values 0 to 9, A to Z, and a to z. It is the first character
of a command. It is usually the number 0 (the default address as shipped from the factory) if data
recorder does not have multiple SDI devices connected to it.
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 that are replaced by actual numbers. Values are entered in the form of a polarity
sign (or ) followed by up to seven digits, including a decimal point.
The command terminator is an exclamation point (!).
NOTE: ALL SDI-12 COMMANDS ARE UPPER CASE.
The SDI-12 AnalogPlus module replies to all SDI-12 commands it supports. If the SDI-12
AnalogPlus module receives a command it does not support, no reply is made. The reply to a
measurement command (M) will have one of two forms:
a0000
Where a is the address and the 0000 indicates that there is no
further message from SDI-12 AnalogPlus module to send
Or
atttn
followed by
a
Where a is the address, ttt is the amount of time, in seconds,
the SDI-12 AnalogPlus module needs to make the
measurement or process the command and n is the number of
values that can be collected. As soon as the measurement is
over, the sensor will also respond with its address (if ttt is not
000). This response is called a service request.
Setting the Address
The default SDI-12 address is 0.
If you are using the SDI-12 AnalogPlus module connected with other SDI-12 devices, you will need
to change the SDI-12 AnalogPlus module 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 SDI-12 AnalogPlus
module supports wildcard addresses of asterisk (*) and question mark (?).
In order to set the address by SDI-12 command, no other SDI-12 devices connected to the system
should be set to address 0 or to the desired SDI-12 AnalogPlus module address.

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Hint: If you do not know the address of a particular SDI-12 AnalogPlus module, use the unknown
address command to have the SDI-12 AnalogPlus module identify itself. There are 3 forms of the
unknown address command:
?!
*!
NOTE: In order for the unknown address command to work, there should be only be one SDI-12
module connected.
The SDI-12 command for setting the SDI-12 AnalogPlus module's address is
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).
The SDI-12 AnalogPlus module will issue a Acknowledge Active response to verify the address set.
If you do not get this message, try the command again
NOTE: The SDI-12 AnalogPlus module will not respond if the command is invalid.
As an example, the following command would set the SDI-12 AnalogPlus module address to 5:
0A5!
Subsequently, the address can be set to a different address, 9 for example, by the command:
5A9!
Verifying the Address and Operation
The SDI-12 AnalogPlus module 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 SDI-12 AnalogPlus module.
The SDI-12 AnalogPlus module will reply with
a13 SUTRON mmmmmm1.0sssssssSvvv , where
a
13
SUTRON
mmmmmm
sssssss
Avvv
SDI-12 address
supports SDI version 1.3 commands
manufacturer SUTRON
model number –will return 1248-1 portion of 6661-1248-1 model number
hardware revision level
reserved space
the software revision
If you do not get a reply, check the address using ?! or *! with no other SDI-12 device connected and
make sure you use the proper address for the sensor.

6
Making a Measurement
There are four classes of measurement commands:
M commands (Measurement Commands - SDI-12 V1.0 and later),
C commands (Concurrent Measurement Commands –SDI-12 V1.2 and later),
MC commands (Measurement commands with CRC-16 –SDI-12 V1.3 and later) and
CC commands (Concurrent Measurement Commands with CRC-16 –SDI-12 V1.3 and later).
Selecting a measurement command class
Always supported
The first requirement is that the data recorder supports 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, utilizing
concurrent commands can shorten the complete data collection cycle. 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.
Example: (M command)
The format of the M command to the SDI-12 AnalogPlus module is:
aM!
a is the address character and
M is the command to make a measurement
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 SDI-12 AnalogPlus module will respond with
attt4
indicating that after ttt seconds are allowed for the
measurement, 4 values can be collected.
When the measurement is complete, the SDI-12 AnalogPlus module responds with a service request
a
where a is the address character

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Note that you still do not have any data from the SDI-12 AnalogPlus module. To request the data
after a measurement,
aD0!
a is the address character and
D0 is the command to retrieve measured data.
Note: the number zero follows D, not the letter O.
C, MC and CC commands
The C command is used to make a concurrent measurement. It operates identical to the M command
except that the SDI-12 AnalogPlus module does not issue a service request when the measurement is
complete.
The MC command is identical to the M command except that the SDI-12 AnalogPlus module adds a
CRC to the end of the data.
The CC command is identical to the C command except that the SDI-12 AnalogPlus module adds a
CRC to the end of the data.
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.
Remember to issue the aD0! Command after the measurement is complete in order to retrieve the
data.
Factory Programmed Default Measurements
From the factory, the following commands will make the defined measurement. Issuing an aXEFD! will also
restore these factory defaults.
All of the measurements, except M, C, MC or CC, can be configured to do other types of measurements or
can have user specific parameters as explained in following sections. The M, C, MC or CC will always return
the analog readings on AN1 - AN4 and cannot be reprogrammed. The Analog measurements assume these
default values:
Averaging Time: 0.067 seconds
Vref Warm-up Time: 10 milli-seconds
Switched Voltage: OFF except in measurement number 6 & 7
Switched Voltage Warm-up time: 100 milli-seconds
Input: Un-Buffered
Gain: Auto-gain
This means that, even though an aM3! from the factory does a frequency measurement, the aM3! command
can be re-programmed to perform any other type of measurement.
M, C, MC, CC
Measure Voltage on channel AN1 through AN4 with respect to ground. 0-5V scale.

8
M1, C1, MC1, CC1
Perform a differential voltage measurement on channel AN2 with respect to channel AN3. +2.5V, but the
voltage on both AN2 and AN3 must be between 0 and 5V.
M2, C2, MC2, CC2
Measure ratio of AN1 voltage to Vref. ( AN1 / Vref)
M3, C3, MC3, CC3
Measure Frequency on channel DIN on a time-scale of 1 second.
M4, C4, MC4, CC4
Perform a differential voltage measurement on channel AN1 with respect to channel AN4. +2.5V, but the
voltage on both AN1 and AN4 must be between 0 and 5V.
M5, C5, MC5, CC5
Measure ratio of AN2 voltage to Vref
M6, C6, MC6, CC6
Measure Voltage on channel AN4. Turn On SW-12volts 100milli-seconds before measurement
M7, C7, MC7, CC7
Measure Voltage on channel AN4. Turn On SW-5volts 100milli-seconds before measurement
M8, C8, MC8, CC8
Measure Period of a signal on channel DIN with maximum Period of three seconds
M9, C9, MC9, CC9
Measure logic level of channel AN4. A low returns 0, and a high returns 1.

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4. Measurements
Setting a Measurement (Quick Set-up With Default Parameters)
When re-programming a measurement command to perform a different type of measurement, it is best to start
with the factory defaults for that measurement type. This makes sure that the measurement has a know good
starting point. NOTE: In all of the following cases, the m (measurement number), is the number that
would follow the issued command, e.g. if setting up the measurement number 1, then to use the re-
programmed measurement, issue an aM1! (or aC1!, aMC1! or aCC1! for concurrent/CRC ). The data
is still retrieved via an aD0!.
Voltage Measurement (Single-ended)
To set-up a voltage measurement on any of the 4 Analog channels, issue the SDI command
aXVm+p+FD!
where,
a: SDI-address of module
m: Measurement number (M command number : 1…9)
p: Measurement channel (1:AN1, 2:AN2, 3:AN3 4:AN4 and V:Vref)
For example, 1XV3+2+FD! will make M3 command in module number 1 to return a single ended voltage
measurement on channel AN2 and with the factory defaults for slope=1.00, offset=0, Averaging-
time=0.067seconds, Vref-warm-up-time=0.010 seconds, no switched voltage, un-buffered input and auto-
gain.
Voltage Measurement (Differential)
To set-up a differential voltage measurement on any of the 2 out of 4 Analog channels, issue the SDI
command aXVm+p+n!
where,
a: SDI-address of module
m: Measurement number (M command number : 1…9)
p: Measurement channel (1:AN1, 2:AN2, 3:AN3 4:AN4 and V:Vref)
n: Reference channel. (1:AN1, 2:AN2, 3:AN3 4:AN4, V:Vref and G:ground)
For example, 1XV3+2+3! will configure the M3 command of the module at SDI-12 address “1” to measure
the voltage on channel AN2 with respect to voltage on channel AN3. The other parameters (slope, offset,
Vref warm-up time, SW‟D voltage, input type and gain) will be left as they were last configured. If it is being
assumed that the values are at the factory defaults, then issue an aXVm+p+FD! command prior to
aXVm+p+n! command to ensure this is true. The factory default values are: slope=1.00, offset=0, Averaging-
time=0.067seconds, Vref-warm-up-time=0.010 seconds, no switched voltage, un-buffered input and auto-
gain.
Ratiometric Measurement
To set-up a ratiometric measurement on any of the 2 out of 4 Analog channels, issue the SDI command
aXRm+p+n!
where,
a: SDI-address of module

10
m: Measurement number (M command number : 1…9)
p: Measurement channel (1:AN1, 2:AN2, 3:AN3 4:AN4 and V:Vref)
n: Reference channel. (1:AN1, 2:AN2, 3:AN3 4:AN4, V:Vref and G:ground)
For example, 1XR3+2+3! will configure the M3 command for the module at SDI-12 address “1” to measure
the ratio of voltage AN2 with respect to AN3. If AN3 is 4Volts and AN2 is 3Volts, then the returned value
will be 0.75 since AN2 is ¾ of AN3. The other parameters (slope, offset, Vref warm-up time, SW‟D voltage,
input type and gain) will be left unchanged.
Tipping-Bucket Measurement
To measure rain-fall, connect tipping bucket between channels DIN (pulled-up) and ground, and issue SDI
command aXBm+FD!
where,
a: SDI-address of module
m: Measurement number (M command number : 1…9)
For example, 1XB4+FD! will configure the M4 command in the module at SDI-12 address “1” measure
rainfall with the factory defaults which are: slope=0.01, offset=0, channel DIN with internal pull-up, initial-
count=0, de-bounce-time=20mS. Note: This takes the module out of a strictly standby mode in that it is
continuously accumulating tips. Measurements return the current accumulation total.
Counts Measurement
To measure Counts on channel D, issue the SDI-12 command
aXCm+FD!
where,
a: SDI-12 address of module
m: Measurement number (M command number : 1…9)
For example, 1XC4+FD! will configure the M4 command in the module at SDI-12 address “1” to measure
the number of counts with the factory defaults which are: slope=1.00, offset=0, channel DIN without a pull-
up or pull-down, initial-count=0, de-bounce-time=0mS. Note: This takes the module out of a strictly standby
mode in that it is continuously accumulating counts. Measurements return the current accumulation total.
Frequency Measurement
To measure Frequency on channel D, issue the SDI-12 command
aXFm+FD!
Where,
a: SDI-address of module
m: Measurement number (M command number : 1…9)
For example, 1XF4+FD! will configure the M4 command in the module at SDI-12 address “1” to measure the
frequency of signal on DIN channel with factory defaults for slope=1.00, offset=0 without any pull-up or pull-
down on the input, de-bounce-time=0mS, no switched voltage on SWD port.
Period Measurement
To measure period of the signal on channel D, issue the SDI-12 command

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aXPm+FD!
Where,
a: SDI-address of module
m: Measurement number (M command number : 1…9)
For example, 1XP4+FD! will configure the M4 command in the module at SDI-12 address “1” to measure the
period of the signal on the DIN channel with the factory defaults of: slope=1.00, offset=0 , without any pull-
up or pull-down, de-bounce-time=0mS, no switched voltage on SWD port.
Quadrature Shaft Encoder Measurement
To set up a Quadrature Shaft Encoder measurement on channel DIN and AN4, issue the following SDI-12
command: aXQm+FD!
Where,
a: SDI-12 -address of module
m: Measurement number (M command number : 1…9)
For example, 1XQ9+FD! will configure the M9 command in the module at SDI-12 address “1” to measure a
Quadrature Shaft Encoder with the factory defaults of feet (assuming a wheel with a 1-foot circumference and
100 counts per rotation) and to set the current-level as the reference(zero). Issuing a 1M9! followed by a 1D0!
will then return two values, the first one will be current level in feet and the second value will be a status byte
that will be one of the following:
0: Okay
64: Level has never been Set
128: Shaft Over-speed detected
192: Level has never been set and Shaft Over-speed has been detected
Notes on Handar 436 Quadrature Ecoder (any switch closure output encoders)
The Handar 436 encoder has open collector / switch closure outputs. Since it does not drive its
outputs high, an external pull-up resistor is required. While the DIN port in the module provides an
internal pull-up for tipping buckets, the shared AN4 input can not have any pull-ups when used for
analog readings.
To configure the module to read the encoder, follow these steps:
1. Configure a measurement command as described above.
2. Connect two 10 K ohm (20%, 1/4 watt or better) resistors between the {sw'd} voltage
and {DIN} and {AN4}.
3. Set the sw'd voltage to a constant +5 volts, using the aXW+5! command.
4. Connect the encoder outputs to the {DIN} and {AN4} inputs.
5. Connect the encoder power to to SDI-12 {+12} and {GND} connections.
To test that the module can now read the encoder, issue the measurement command (to what ever
command number above was used), and then issue the aD0! command to read the current level. Then
rotate the encoder and measure the encoder again to see that the reading changed (i.e for a 1 foot
wheel, verify one rotation returns 1 foot of change).

12
State of Port
The module supports reading the state of any of the 5 inputs. The SDI-12 command to configure this
measurement is aXSm+p+t!
where,
m: Measurement number (M command number : 1…9)
p : Measurement channel
t : Threshold voltage (0.5Vmin, 4.5V max) for state determination. Default is 1.25V
For example, for the module at SDI-12 address “1”, if you want the M6 measurement to return 1 if voltage
on AN3 is greater than or equal to 1.9 volts and 0 if less than 1.9 volts, use 1XS6+3+1.9!

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Setting a Measurement (Specific Set-up With User-Defined Parameters)
Voltage Measurement
The module has four analog ports to take analog voltage measurements. The voltage can be measured single-
ended (with respect to ground) or differential (between 2 channels or between a channel and Vref). The
measurement is done using a high precision delta-sigma, Analog-to-Digital (A/D) converter, which can be
programmed for following parameters:
Input Channels
Digital Filter for different data-output rate (averaging time) to get different line rejection frequencies
Buffered or Non-Buffered input
Input Gain of 1, 2, 4, 8, 16, 32, 64, or 128
In addition to this, you can specify
Slope: A multiplier to convert voltage reading to a different engineering unit
Offset: A constant value to be added to the result after adjusting it with Slope
Vref Warm-up Time: Time Vref should be turned on before taking a measurement
Switched Voltage: This can be set to 5volts or 12volts if sensor requires an external excitation
voltage
Switched Voltage Warm-up time: Time switched voltage should be present before taking a
measurement.
SDI-12 set-up command
To set-up a voltage measurement or change a parameter (other than default), you can use the SDI command
aXVm+p+n+s+o+t+v+w+x+i+g!
where,
a: SDI-address of module
m: Measurement number (M command number : 1…9)
p: Measurement channel (1:AN1, 2:AN2, 3:AN3 4:AN4 and V:Vref)
n: Reference channel. Default is ground
s: Slope. Default is 1.00
o: Offset. Default is 0.00
t: Averaging time (less than 0.09 for 15Hz, greater than 0.09 and less than 0.19 for 7.5Hz, greater than 0.19
for 3.75Hz). Default is 0.067.
v: Vref warm-up time. Default is 0.010,i.e. 10mS
w: Switched voltage during measurement ( = 0, 5 or 12). Default is 0
x: Switched voltage warm-up time in sec. Default is 0.1, i.e.100mS
i: U=Unbuffered, B=Buffered. Default is U
g: Gain = 0, 1, 2, 4, 8, 16, 32, 64, 128. Default is 0, which means auto-gain
You can do a quick set up by selecting channels only. For the omitted parameters, the module will retain the
previously specified value. To ensure that unspecified parameters are at factory defaults, suffix the
measurement channel with “+FD”.

14
Examples
To set M3 to measure voltage on AN2 with all other parameters set to factory default, use
1XV3+2+FD!
Which will configure the M3 command in the module at SDI-12 address “1” to measure voltage on
channel AN2 with the factory defaults of: slope=1.00, offset=0, Averaging-time=0.067seconds,
Vref-warm-up-time=0.010 seconds, no switched voltage, un-buffered input and auto-gain.
If M3 is currently set to measure something other than voltage, then
1XV3+2! is equivalent to 1XV3+2+FD!
Note: An „FD‟ except in place of reference channel is invalid, i.e.
1XV3+FD! or
1XV3+2+3+FD! or
1XV3+2+3+2.0+FD!
are all invalid commands
To set M3 to measure the voltage on AN2 with a switched voltage of 5volts and all other parameters
set to factory default, first use
1XV3+2+FD! and then
1XV3+X+X+X+X+X+X+5!
All the X‟s in the example except the 2nd „X‟ means “leave the parameter unchanged” (factory
default in this example).
Note: Using 1XV3+2+X+X+X+X+X+5! instead of sequence of two commands, in above example, will
also do the same but the parameters substituted by „X‟ may or may not be factory defaults. They
depend on what M3 was configured for prior to this set-up. If M3 is set for something other than
voltage, then parameters substituted by „X‟ will be default voltage-measurement parameters.
If M3 is set to measure voltage and you need to change just few parameters, say Vref-warm-up time
to 30 milli-seconds, use
1XV3+X+X+X+X+X+0.03!
Verification and Reading current Set-up
There are 3 options to read set-up
1. aD0 command after XV command
2. aXVm command (1XV3! in our examples)
3. aXGm and aXGm+2 commands (1XG3! And 1XG3+2! in our examples)
All of the different kinds of set-up commands return
10027<CR><LF> (it may be 3 instead of 1 depending on SDI-12 AnalogPlus module address)
which means it will return 7 parameters on a successive D0 command after 2 seconds. The response
to D0 is
1+s+o+t+v+w+x+g<CR><LF> (the alphabetic characters in lower-case have the same meaning as
mentioned above).
You won‟t see channel information and input type because SDI-12 command D0 can not return an
alphabetic character. To determine the channel set-up of the voltage measurement on M3, you may
use the
1XV3!
Command which returns
1+p+n+s+o+t+v+i+g<CR><LF> or
1+NC<CR><LF> if M3 is not configured to measure voltage.