Xylem H-4161 User Manual

Model

H-4161

SDI-12 to 4-20mA Interface

Owner's Manual

Version 1.2

75 West 100 South, Logan, Utah 84321 Phone: [phone] Fax: [phone] Web: http://www.waterlog.com E-mail: [e-mail]

D E S I G N A N A L Y S I S A S S O C I A T E S , I N C .

75 West 100 South, Logan, Utah 84321 Phone: [phone] Fax: [phone] Web: http://www.waterlog.com E-mail: [e-mail]

D E S I G N A N A L Y S I S A S S O C I A T E S , I N C .

User Agreement/

W

ATER

1. NATURE OF THE PRODUCT

This agreement accompanies an interface module comprising firmware, circuitry and other electronic
equipment in an enclosed housing, and packaged together with written instructional materials. The
packaged electronic circuitry and instructional materials herein are collectively referred to as the
“PRODUCT.” The PRODUCT is made available from DESIGN ANALYSIS ASSOCIATES, INC., of
75 West 100 South, Logan, Utah 84321 (hereinafter referred to as “DESIGN ANALYSIS”), and contains
information and embodies technology that is confidential and proprietary to DESIGN ANALYSIS, and
the availability and use of the PRODUCT is extended to you, the USER, solely on the basis of the terms
of agreement which follow.

2. ACKNOWLEDGMENTS BY USER

Opening the package which encloses the accompanying PRODUCT indicates your acceptance of the
terms and conditions of this agreement and constitutes an acknowledgment by you of the confidential and
proprietary nature of the rights of DESIGN ANALYSIS in the PRODUCT.

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In consideration for the access to and use of the PRODUCT extended to you by DESIGN ANALYSIS
and to protect the confidential and proprietary information of DESIGN ANALYSIS, USER agrees as
follows:

LOG® Warranty

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safety warnings or notices of proprietary interest placed thereon by DESIGN ANALYSIS.

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(c) USER agrees to treat the PRODUCT with the same degree of care as USER exercises in relation to

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USER may enjoy these rights only as long as their possession of the PRODUCT shall continue to be
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any redemption offer, warranty, or money-back guarantee, or if USER transfers the PRODUCT to
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5. LIMITED WARRANTY
(b) What is Covered

DESIGN ANALYSIS warrants that for a period of twelve months from the time of purchase the
functions to be performed by the PRODUCT will be substantially in compliance with USER
documentation. DESIGN ANALYSIS also warrants that the PRODUCT will be free from
defects in materials and workmanship for a period of ONE YEAR from the date of purchase.

(b) What USER Must Do

If the product fails to satisfy the above warranty, USER must notify DESIGN ANALYSIS in
writing within the applicable period specified above and reasonably cooperate with the directions
they received from DESIGN ANALYSIS.

H-3611

User Agreement/W

ATER

LOG® Warranty W-1

(c) What DESIGN ANALYSIS Will Do

DESIGN ANALYSIS will repair the PRODUCT or will endeavor to provide a replacement of
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W-2 User Agreement/W

ATER

LOG® Warranty

H-4161

Chapter 1

Introduction

1.0 Introduction

The W

ATER

LOG® H-4161 is a SDI-12 to two-wire 4-20mA interface module. The H-4161 can be

programmed to either monitor communications between a data logger and its attached sensors or to
initiate measurements by itself. The measurement data is scaled as needed and output to a precision two­wire 4-20mA current transmitter.

Figure 1 H-4161 SDI-12 to 4-20mA Interface

The “SDI-12 Serial-Digital Interface” is ideal for data logging applications with the following
requirements:



Battery powered operation with minimal current drain



Low system cost

The H-4161 has the following features:

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Precision 16-bit 4-20mA current output

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1000V output isolation from the SDI-12 bus

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Can monitor the SDI-12 bus for a specified sensor address and data parameter

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Can initiate measurements to an attached sensor

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Programmable “Max” and “Min” data set points for automatic data scaling

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Manual “set” of the 4-20mA output using an extended SDI-12 command



Two SDI-12 ports

H-4611

Introduction 1-1

1.1 Description

The H-4161 includes a microprocessor, LCD display, 16-bit digital-to-analog converter, precision voltage
reference and a 4-20mA current transmitter. The SDI-12 and 4-20mA sections are isolated from each
other with a high voltage digital opto-coupler. Data collected from the SDI-12 bus is scaled by the
microprocessor into a 16-bit value and loaded into the digital-to-analog converter. The digital-to-analog
converter directly controls the current transmitter.

The H-4161 has two SDI-12 ports. The primary SDI-12 port provides data monitoring and
communication with the H-4161 device itself. When programmed to initiate measurements, the H-4161
makes measurements and collects the data from a sensor connected to the auxiliary SDI-12 port.

1.2 Display

The H-4161 has a 2-line x 16-character Liquid Crystal Display (LCD) which shows the current
measurement data. Line-1 displays the most recently captured SDI-12 data parameter. If the sensor
buffer is invalid (no data captured or the previous measurement failed) the message “no data” is shown
instead of a number. Line-2 displays the current setting of the 4-20mA output. Note: the mA value is the
desired loop current setting which the microprocessor loads into the digital to analog converter. If the 4­20 mA loop is open, or insufficient loop voltage is present the actual loop current may be zero or may not
match the value on the display.

SDI = xxx.xx ft ­Iout = xx.xx mA

The character on the right hand side of Line-1 is an activity “spinner”. Every time a measurement is
captured or initiated, the spinner changes (rotates). This indicator shows measurements are being made
even if the measurement data is static (not changing).

1.3 Connectors

The H-4161 has a 5-position connector for making +12V and SDI-12 connections. The primary SDI-12
terminal is connected to the data logger and it’s attached sensors. If the H-4161 is to initiate
measurements, the auxSDI-12 terminal is connected to the SDI-12 sensor to be monitored. The 2­position connector is for making connections to the 4-20mA loop.

1-2 Introduction

H-4161

1.4 Monitor SDI-12 Communications (Module Mode = 0)

During normal operation the data recorder sends commands to one or more SDI-12 sensors and
subsequently collects data from the sensors. As a “data monitor”, the H-4161 passively monitors the
communication between the data recorder and its SDI-12 sensors. The H-4161 waits for, and collects a
specified data parameter from a specified sensor. The data is scaled and used to update the H-4161's 4­20mA output. In this mode the H-4161 monitors, but does not transmit data to the SDI-12 bus. The data
recorder must initiate any sensor measurements.

The data recorder can also communicate with the H-4161 directly as a normal SDI-12 “sensor”. Using
extended SDI-12 commands, the data recorder/user can manually set the 4-20mA output, observe the last
data collected or configure the H-4161.

Figure 2 The H-4161 monitors the SDI-12 bus for a selected

parameter

H-4611

Introduction 1-3

1.3 Initiate Measurements (Module Mode = 1)

Applications often arise where is it desired to connect a SDI-12 sensor directly to a 4-20mA input device
such as a PLC without the use of a data logger. When programmed to initiate measurements, the H-4161
sends 0M! (or 0M1 to 0M9) commands to the sensor attached to the auxSDI-12 port and collects the
measurement data. The data is scaled and used to update the H-4161's 4-20mA output.

The Initiate Measurement mode also provides support for a hybrid architecture employing both a data
logger and PLC. Both the primary and auxSDI-12 ports can be used. For example, the following
illustration shows a dam equipped with sixteen SDI-12 gate position sensors (inclinometers). Each gate
is equipped with a H-4161 module which initiates measurements and sends 4-20mA data to the PLC. All
16 channels make simultaneous measurements. The radial architecture provides near real-time gate
position data to the PLC. The system also has a data logger which periodically collects the gate position
and other data on a timed schedule. The data logger sends “aM!” measurement commands to each H­4161 and collects the resulting data, channel-by-channel. The measurement data collected in response to
the “aM!” command will be the data from the most recent measurement made by the H-4161 to the
sensor on the auxSDI-12 port (no actual “measurement” is made). The H-4161 supports simultaneous
SDI-12 commands/responses on both the primary and auxSDI-12 ports. The data logger can collect gate
position data without disturbing any measurements currently in progress with the gate position sensors.

Figure 3 Example architecture with sixteen 4-20mA channels and a data logger

..

1-4 Introduction

H-4161

Chapter 2

Installation And Maintenance

2.1 General Installation Recommendations

The enclosure and connectors are not weather tight. The H-4161 must be installed in a protected location
or a weather tight enclosure. The enclosure has a 5-terminal connector for making power and SDI-12
connections and a 2-terminal connector for connecting the 4-20mA output connections. The connectors
can be detached while making the connections.

Caution: Remove all power from the unit before making any connections.

Before beginning the installation take a minute to plan out your station grounding and wiring scheme.

2.2 Making Power and SDI-12 connections

Connect the +12V and GND terminals to a 12V power source. If the H-4161 is to be used to Monitor,
connect the primary SDI-12 data terminal to the SDI-12 bus between your data logger and its sensors. If
the H-4161 is to be used to Initiate, connect the auxSDI-12 terminal to the sensor to be monitored. The
sensor address of the sensor connected to the auxSDI-12 terminal must be “0" (this cannot be changed in
the H-4161). The sensor address must be set before connecting the sensor to the H-4161.

2.3 Making the 4-20mA connections

The H-4161 has a 2-wire “self powered” current loop transmitter. Current loop sensors output a current
rather than a voltage. The 4-20mA output will drive standard industrial telemetry and process control
instrumentation. Use shielded twisted-pair cable and take precautions to protect the wiring from noise
and interference. Your loop power source, loop receiver and the H-4161's output should all be connected
in series. The loop power supply must be sufficient to maintain 5.5V to 35V across the H-4161s output
terminals, in addition to whatever voltage is needed to maintain 20mA across the loop receiver and
interconnect wiring. The gauge station +12.0V SDI-12 power source will work if the resistance of your
loop receiver and wiring is less than 250 ohms.

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Make certain their is 5.5 to 35V across the 4-20mA output terminals.



Make certain the H-4161 is receiving +12V power from the SDI-12 data bus.



Use shielded, twisted-pair cables for the 4-20mA connections in noisy environments.

H-4161

Installation And Maintenance 2-1

Note:

The SDI-12 logic and the 4-20mA interface are isolated from each other by digital optical isolators. The
SDI-12 logic is powered from the +12V input terminal, the 4-20mA circuitry is self-powered from the 4­20mA loop. When the H-4161 is first powered up, the output current is set to 4.0mA. It remains at

4.0mA until the first successful data collection sequence. If the loop power is disconnected or is applied

after the SDI-12 side is powered up, the data in the digital-to-analog converter will be undefined. When
the loop power is restored, the 4-20mA output will be at an unknown value. Once a fresh SDI-12 data
collection is made the digital-to-analog converter will be loaded with new valid data.

2.4 Programming the H-4161

The H-4161 comes from the factory with the following settings:

H-4161 device address 0
Max setpoint: 20.00
Min setpoint: 4.00
Monitored Address: Z
Monitored Parameter: 1
AutoScan Command: 0 (0M!)
Module Mode: 0 (monitor)
Measurement Rate: 0 (seconds)

These setups are stored in Flash memory within the H-4161 and will not be lost if the power is removed.
The extended commands for changing these settings are described in detail in Chapter 3.

2.5 Programming the Sensor Address

The H-4161 comes from the factory with its sensor address set to “0". If more than one sensor is to be
connected to the SDI-12 bus, make certain each sensor has a unique sensor address, including any H­4161 modules. The H-4161 is not a traditional sensor and does not ‘make measurements”. However, to
facilitate programming the H-4161 it must have a unique address.

2.6 Programming the Max and Min data setpoints

Captured SDI-12 data is scaled into 4-20mA units using the programmable Max and Min data setpoints.
This feature makes it easy to setup the H-4161 for your application. For example, if you are monitoring
stream stage which could be up to 10 feet, program the Max setpoint to 10.00. Perhaps the stream never
falls below 5 feet and you would like to narrow the dynamic range of the 4-20mA output for more
resolution. In this case program the Min setpoint to 5.00. A captured SDI-12 data value of 5.00 will
produce a 4.0 mA output and data value of 10.00 will produce 20.0mA. Note if the stage rises above

10.0 feet the output will clamp at 20mA or if the stage falls below 5 feet the output will clamp at 4.0mA.

The extended commands to examine or change the Min and Max values are explained in Chapter 3.

2-2 Installation And Maintenance

H-4161

2.7 Programming the Module Mode setting

The H-4161 can either “monitor” SDI-12 communication between a data logger and its sensors, or
“initiate” measurements to a dedicated sensor connected to the auxSDI-12 terminal. The H-4161 comes
from the factory with Module Mode = 0 (monitor). The extended commands to examine or change the
Module Mode are explained in Chapter 3.

2.8 Programming the Monitored Address setting

As a data monitor, the H-4161 passively monitors communication between the data recorder and its SDI­12 sensors. The H-4161 waits for, and collects data from a specified sensor. The data recorder must
initiate any sensor measurements. The H-4161 comes from the factory with the Monitored Address = Z.
If you wish to monitor data from another sensor you must change the monitored address to the desired
value. This setting is not used if Module Mode = 1 (initiate). The extended commands to examine or
change the Monitored Address are explained in Chapter 3.

2.9 Programming the Monitored Parameter setting

Each SDI-12 sensor can make up to nine separate measurements or “parameters”. The data recorder
collects the measurement data using “aD0!” - “aD9!” commands. The Monitored Parameter setting
controls which of the nine data parameters is to be monitored by the H-4161. The H-4161 also monitors
the data sent in response to the new concurrent SDI-12 V1.2 “aR0" data collection commands. The H­4161 comes from the factory with Monitored Parameter = 1. This setting should work with most
sensors. The extended commands to examine or change the Monitored Parameter are explained in
Chapter 3.

2.10 Programming the AutoScan Command setting

When the Module Mode =1 (initiate), the H-4161 actively initiates measurements and collects the
response from the sensor attached to the auxSDI port. The H-4161 normally issues an “0M!” command
to the auxSDI port. If desired, the H-4161 can be programmed to issue other commands such as “0M1!”
(“0M1" to “0M9!”). The extended commands to examine or change the AutoScan Command are
explained in Chapter 3.

2.11 Programming the Measure Rate setting

When Module Mode = 1 (initiate), the H-4161 initiates measurements to the sensor attached to the
auxSDI port. The measurement interval is controlled by the Measure Rate setting. If the Measure Rate
is set to a value less than the time it take to make the actual measurement, measurements will be made
back-to-back, as fast as possible. The H-4161 comes from the factory with Measure Rate = 0 (seconds).
This setting is not used if Module Mode = 0 (monitor).

H-4161

Installation And Maintenance 2-3

2.12 Testing with Module Mode = 0 (monitor)

Use the following procedure to verify your H-4161 is working properly. These tests will also help you
understand how the H-4161 works.

1. Make the connections to the SDI-12 input and the 4-20mA output. Connect the sensor to be monitored

to your data logger. Your loop power source, loop receiver and the H-4161's output should all be
connected in series. In addition, temporarily connect a current meter in series with the 4-20mA loop.



Make certain there is 5.5 to 35V across the 4-20mA output terminals.



Make certain the H-4161 is receiving +12V power from the SDI-12 data bus.

2-4 Installation And Maintenance

H-4161

Use the Transparent SDI-12 mode of your data recorder to issue and monitor the following SDI-12
commands

2. Check to see if you can communicate with the H-4161.
Issue a “0I!” Identify command.
The H-4161 should respond with: “012 DAAH-4161001S#000000V10<CR><LF>”

3. Check to see if the H-4161's self-test is ok.
Issue a “0V!” Verify command.
The H-4161 should respond with: 00011<CR><LF>
Issue a “0D0" command to collect the data.
The H-4161 should respond with: 0+1<CR><LF>

4. Check to see if the H-4161's 4-20mA output is working by using the “Set Milliamp” command.
Issue a “0XSM10.0!” command.
The H-4161 should respond with: I-Out=10.0<CR><LF>
This sets the H-4161s output to 10.0mA .
Check to see if the current meter you installed in Step 1 shows 10.0 mA flowing in the loop.
Experiment with different current settings using the XSMnnn command. Make certain your loop
works at the 4.0 and 20.0 mA endpoints.

Next, check to see if the H-4161 can successfully capture sensor data from your SDI-12 sensor and scale
it into 4-20mA.

5. Program the Max and Min setpoint as needed for your application, set the Monitored Address setting

as needed. In these examples the address of the sensor to be monitored is “Z”. Experiment with the
“aXSCSddd” command to make certain your Max and Min settings are correct.

6. Issue a “ZM!” measurement command to cause your SDI-12 sensor to make a measurement.

Your sensor should respond with Ztttnn<CR><LF>

where: a is the SDI-12 sensor address

ttt is a three digit integer specifying the maximum time, in seconds

the sensor will take to complete the command and have data
available in its buffer
n is a single digit integer specifying the number of values that will be
placed in the data buffer

H-4161

Installation And Maintenance 2-5

7. Issue an “ZD0!” command to collect data from your SDI-12 sensor. The H-4161 monitors and
captures the response. Your SDI-12 sensor should respond with “Z+nnn.n<CR><LF>” or similar.

8. Issue a “0M!” command to “measure” the data value collected by the H-4161. The H-4161 should
respond with: 00001<CR><LF>

9. Issue a “0D0!" command to collect the captured data value from the H-4161. The H-4161 should
respond with: 0+nnn.nn<CR><LF>

+nnn.nn is the data value captured from your sensor by the H-4161, this value should match the data
value measured by your sensor in Step 7. The value must be between the Min and Max set point settings
of the H-4161 or the output will be clamped at either 4.0mA or 20mA respectively.

Use the following equation to calculate the current which should be output by the H-4161. Compare this
value with the reading displayed by the current meter installed in Step 1. Note, if the loop power is
removed or applied after the data collection sequence of Step 7 was completed, the output of the H-4161
will be a random current value until a new measurement sequence is performed.

where: Xdata = nnn.nn as measured by your sensor

MAX = the Max setpoint of the H-4161
MIN = the Min setpoint of the H-416

1

2.13 Testing with Module Mode = 1 (initiate)

Use the following procedure to verify your H-4161 is working properly. These tests will also
help you understand how the H-4161 works.

1. Make the connections to the +12V power and the 4-20mA output. Connect the sensor to be
monitored to the auxSDI-12 port. Make certain the address of this sensor is “0". If you wish to
experiment with the measure rate or other settings, connect a data logger to the primary SDI-12
data port. Your loop power source, loop receiver and the H-4161's output should all be connected
in series. In addition, temporarily connect a current meter in series with the 4-20mA loop.



Make certain there is 5.5 to 35V across the 4-20mA output terminals.



Make certain the H-4161 is receiving +12V power from the SDI-12 data bus.

2-6 Installation And Maintenance

H-4161

Use the Transparent SDI-12 mode of your data recorder to issue and monitor the following SDI­12 commands

1. Set Module Mode = 1 (See chapter 3).

2. Program the Max and Min setpoint as needed for your application, set the Monitored
Parameter setting as needed.

3. Check to see if the H-4161's 4-20mA output is working by using the “Set Milliamp”
command.
Issue a “0XSM10.0!” command.

The H-4161 should respond with: I-out=10.0<CR><LF>
This sets the H-4161s output to 10.0mA . Check to see if the current meter you
installed in Step 1 shows 10.0 mA flowing in the loop.
Note: your setting will soon be overwritten when the next initiated measurement is made.

Experiment with different current settings using the XSMnnn command. Make certain
your loop works at the 4.0 and 20.0 mA endpoints. Experiment with the “aXSCSddd”
command to make certain your Max and Min settings are correct.

4. The H-4161 should be making measurements to the sensor attached to the auxSDI-12 port in a
tight loop. Check the 4-20mA output for the expected response.

5. Change the Measure Rate as needed. Check for the expected response with an oscilloscope or
other means to detect when a measurement is initiated.

2.14 Transparent Mode

When the Module Mode = 1 (Initiate), the H-4161 actively initiates measurements and collects
the response from the sensor attached to the auxSDI port. During setup and testing it may be
useful for the user to access the sensor attached to the auxSDI port without changing the wiring
or connectors. When activated (see Chapter 3), the Transparent mode causes the H-4161 to stop
making measurements on the auxSDI port and to make a virtual connection between the primary
and auxSDI ports. While the Transparent Mode is active, all communication to/from the H­4161's address is passed thru to the auxSDI port. The “aM!”, “aD0!” and other internal
commands of the H-4161 are disabled and the H-4161 is essentially replaced by the sensor
attached to the auxSDI port.. The Transparent Mode is automatically deactivated when the H­4161 detects an access to any sensor address other than its own. Note: the sensor address
character of each command is forced to “0" by the H-4161 before being forwarded to the auxSDI
port.

H-4161

Installation And Maintenance 2-7

2-8 Installation And Maintenance

H-4161

Chapter 3

SDI-12 Command and Response Protocol

3.0 SDI-12 Command and Response Protocol

This is a brief description of the Serial Digital Interface (SDI-12) Command and Response
Protocol used by the W
commands and data format supported by the H-4161.

Refer to the document "A SERIAL DIGITAL INTERFACE STANDARD FOR HYDROLOGIC
AND ENVIRONMENTAL SENSORS.” Version 1.2 April 12, 1996 Coordinated by the SDI-12
Support Group, 135 East Center, Logan, Utah.

During normal communication, the data recorder sends an address together with a command to
the H-4161 SDI-12 interface. The H-4161 then replies with a "response." In the following
descriptions, SDI-12 commands and responses are enclosed in quotes. The SDI-12 address and
the command/response terminators are defined as follows:

"a" Is the sensor address. The following ASCII Characters are valid addresses:

ATER

LOG® Series Model H-4161 sensor. Included is a description of the

"0-9", "A-Z", "a-z", "*", "?". Sensors will be initially programmed at the

factory with the address of "0" for use in single sensor systems. Addresses

"1 to 9" and "A to Z" or "a to z" can be used for additional sensors

connected to the same SDI-12 bus. Address "*" and "?" are "wild card"

addresses which select any sensor, regardless of its actual address.

Notes:

"!" Is the last character of a command block.

"<cr><lf>" Are carriage return (0D) hex and line feed (0A) hex characters. They are

the last two characters of a response block.

• All commands/responses are upper-case printable ASCII characters.

• Commands must be terminated with a "!" character.

• Responses are terminated with <cr><lf> characters.

• The command string must be transmitted in a contiguous block with no gaps of more
than 1.66 milliseconds between characters.

H-4161

SDI-12 Command and Response Protocol 3-1

3.1 Command Summary

The H-4161 supports the following SDI-12 commands:

Standard Commands:

aM! Make measurement
aM1! Make special measurement
aD0! Send Data
aV! Verify
aI! Send Identification
a! Send Acknowledge
aAn! Change Address

Extended Commands:

aXTEST! Displays the current module settings
aXHELP! Displays the supported commands
aXRMM! Read Module Mode (0=Monitor, 1=Initiate)
aXWMMn! Write Module Mode (0=Monitor, 1=Initiate)
aXRMA! Read Monitored Address (0-9, A-Z, a-z)
aXWMAn! Write Monitored Address (0-9, A-Z, a-z)
aXRMP! Read Monitored Parameter (1 to 9)
aXWMPn! Write Monitored Parameter (1 to 9)
aXRAC! Read AutoScan command setting (0 to 9)
aXWACn! Write AutoScan command setting (0 to 9)
aXRMR! Read Measure Rate (seconds)
aXWMRdd! Write Measure Rate (seconds)
aXSTM! Set Transparent Mode

aXRIH! Read High (max) data value for 20.0mA
aXWIHdd! Write High (max) data value for 20.0mA
aXRIL! Read Low (min) data value for 4.0mA
aXWILdd! Write Low (min) data value for 4.0mA
aXSCSdd! Set Current Stage (for testing 4-20mA)
aXSMdd! Set Milliamp output (for testing 4-20mA)

Factory use only:

aXSDACdd! Set the DAC to dd counts (for testing 4-20mA)
aXSCL! Set Calibration Low (DAC=500)
aXSCH! Set Calibration High (DAC=65000)
aXRCL! Read DAC Calibration Low
aXWCLdd! Write DAC Calibration Low
aXRCH! Read DAC Calibration High
aXWCHdd! Write DAC Calibration High

3-2 SDI-12 Command and Response Protocol

H-4161

3.2 Measure Command

The H-4161 is not a normal SDI-12 sensor and does not make sensor “measurements”. Instead,
the Measure command copies the most recently captured SDI-12 data parameter. If the module
mode is “Monitor”, the aM! can be used to read the most recent data the H-4161 has captured. If
the module mode is “Initiate”, the aM! command reads the most recent measurement made on the
auxSDI port.

Data values generated in response to this command are stored in the sensor's buffer for subsequent
collection using "D" commands. The data will be retained in the sensor until another "M", " C",
or "V" command is executed.

Command Response Description
"aM!" "atttn<cr><lf>" Initiate measurement

Where:

a is the sensor address ("0-9", "A-Z", "a-z", "*", "?").

M is an upper-case ASCII character

ttt is a three digit integer (000-999) specifying the maximum time, in seconds, the

sensor will take to complete the command and have measurement data available in
its buffer.

n is a single digit integer (0-9) specifying the number of values that will be

placed in the data buffer. If "n" is zero (0), no data will be available using
subsequent "D" commands.

Upon completion of the measurement, a service request "a<cr><lf>" may be sent to the data
recorder indicating the sensor data is ready. The data recorder may wake the sensor with a break
and collect the data any time after the service request is received or the specified processing time
has elapsed.

The aM! command takes 0 seconds to complete and places 1 value in the sensor buffer, no service
request is sent.

Example of a H-4161 "aM!" command:

Command Response Time Values Description
"aM!" "a0001<cr><lf>" 0 sec 1 Make measurement

Subsequent Command Response
"aD0" a+AA.AAA<cr><lf>

where: AA.AAA = Most recent measurement (feet, inches, meters etc.)

H-4161

SDI-12 Command and Response Protocol 3-3

The “aM1!” command is similar to the “aM!” command, however it places additional information
in the sensor buffer. If a data parameter has not been captured, the message “no data” is placed in
the sensor buffer.

During debug and testing this feature is useful for determining if the H-4161 is properly and
reliably capturing the monitored parameter. The recommended test procedure is to configure the
data logger to make a H-4161 “aM1!” measurement at the completion of the sensor scan.
Configure the data logger to record both the captured measurement and the calculated (desired)
mA parameters. During the sensor scan the data logger first initiates a measurement and collects
measurement data from the sensor being monitored. The H-4161 independently captures and
processes the monitored parameter. At the completion of the sensor scan the data logger issues an
“aM1!” command to the H-4161 and collects the response. The captured parameter value should
always match the data value the data logger previously collected from the sensor. Examine the
logged data to make certain the data is being captured and processed into the proper mA setting.

Example of a H-4161 "aM1!" command:

Command Response Time Values Description
"aM!" "a0014<cr><lf>" 1 sec 4 Make measurement

Subsequent Command Response
"aD0" a+AA.AAA+BB.BBB+CC.CC+DD.DD<cr><lf>

where: AA.AAA = Most recent measurement (feet, inches, meters etc.)

BB.BBB = Calculated (desired) mA setting for this measurement
CC.CC = Current Min (low) data setting (see “aXRIL!” command)
DD.DD = Current Max (high) data setting (see “aXRIH!” command)

3-4 SDI-12 Command and Response Protocol

H-4161

3.3 Concurrent Measurement Command

This is a new command for the Version 1.2 SDI-12 Specification. A concurrent measurement is
one which occurs while other SDI-12 sensors on the bus are also taking measurements. This
command is similar to the “aM!” command, however, the nn field has an extra digit and the
sensor does not issue a service request when it has completed the measurement. Communicating
with other sensors will NOT abort a concurrent measurement. Data values generated in response
to this command are stored in the sensor's buffer for subsequent collection using "D" commands.
The data will be retained in the sensor until another "M", "C", or "V" command is executed.

Command Response Description
"aC!" "atttnn<cr><lf>" Initiate measurement

Where:

a is the sensor address ("0-9", "A-Z", "a-z", "*", "?").
C is an upper-case ASCII character
ttt is a three digit integer (000-999) specifying the maximum time, in seconds, the

sensor will take to complete the command and have measurement data available in
its buffer.

nn is a two digit integer (00-99) specifying the number of values that will be

placed in the data buffer. If "n" is zero (0), no data will be available using
subsequent "D" commands.

The data recorder may wake the sensor with a break and collect the data anytime after the
specified processing time has elapsed.

H-4161

SDI-12 Command and Response Protocol 3-5

3.4 Send Data Command

The Send Data command returns sensor data generated as the result of previous "aM!", "aC!", or
"aV!" commands. Values returned will be sent in 33 characters or less. The sensor's data buffer
will not be altered by this command.

Command Response
"aD0!" "apd.d<cr><lf>"

Where:

a is the sensor address ("0-9", "A-Z", "a-z", "*", "?").

D0 are upper-case ASCII characters.

p Is a polarity sign (+ or -)

d.d represents numeric digits before and/or after the decimal. A decimal may be used

in any position in the value after the polarity sign. If a decimal is not used, it will
be assumed to be after the last digit.

For example: +3.29 +23.5 -25.45 +300

If the "aD0!" returns no data (“a<cr><lf>” only), it means that no measurement data is available
(or the measurement was aborted) and a new "M" command must be sent. If the module mode is
“MONITOR”, an “a<cr><lf>” response indicates no measurement has been captured. If the
module mode is “INITIATE”, an “a<cr><lf>” response indicates the most recent measurement on
the AuxSDI port has failed.

Example of a H-4161 "aD0!" command:

Previous Command Response

"aM!" "a0001<cr><lf>"

Subsequent Command Response

"aD0" a+AA.AAA<cr><lf>

Where:

AA.AAA = Most recent measurement (feet, inches, meters etc.)

3-6 SDI-12 Command and Response Protocol

H-4161

3.5 Send Acknowledge Command

The Send Acknowledge Command returns a simple status response which includes the address of the
sensor. Any measurement data in the sensor's buffer is not disturbed.

Command Response
"a!" "a<cr><lf>"

Where: a Is the sensor address ("0-9", "A-Z", "a-z", "*", "?").

3.6 Initiate Verify Command

The Verify Command causes a verify sequence to be performed. The result of this command is similar to
the "aM!" command except that the values generated are fixed test data and the results of diagnostic
checksum tests. The data generated in response to this command is placed in the sensor's buffer for
subsequent collection using "D" commands. The data will be retained in the sensor until another "M",
"C", or "V" command is executed.

Command Response Description
"aV!" "atttn<cr><lf>" Initiate verify sequence

Where:

a is the sensor address ("0-9", "A-Z", "a-z", "*", "?").

V is an upper-case ASCII character.

ttt is a three digit integer (000-999) specifying the maximum time, in seconds, the sensor will

take to complete the command and have data available in its buffer.

n is a single digit integer (0-9) specifying the number of values that will be

placed in the data buffer. If "n" is zero (0), no data will be available using
subsequent "D" commands

Example of a "aV!" command:

Command Response Time Values Description
"aV!" "a0014<cr><lf>" 1 sec 4 Return fixed data and diagnostic data for testing

purposes.

Subsequent Command Response
"aD0" a+123.456+78.9+x+y<cr><lf>

Key Description Units
+123.456 Fixed test data
+78.9 Fixed test data
x Memory checksum 0-65535
y ROM checksum test 0 = Failed, 1 = Passed

H-4161

SDI-12 Command and Response Protocol 3-7

3.7 Send Identification Command

The Send Identification Command responds with sensor vendor, model, and version data. Any
measurement data in the sensor's buffer is not disturbed.

Command Response
"aI!" "allccccccccmmmmmmvvvxx...xx<cr><lf>"

Where:

a is the sensor address ("0-9", "A-Z", "a-z", "*", "?").

I is an upper-case ASCII character.

ll is the SDI-12 version compatibility level, e.g. version 1.2 is represented as

"12".

cccccccc is an 8 character vendor identification to be specified by the vendor and

usually in the form of a company name or its abbreviation.

mmmmmm is a 6 character field specifying the sensor model number.

vvv is a 3 character field specifying the sensor version number.

xx...xx is an optional field of up to a maximum of 13 characters to be used for

serial number or other specific sensor information not relevant to operation
of the data recorder.

Example of a "aI!" command:

"a12 DAA H-4161vvvS#nnnnnnVkkk<cr><lf>"

H-4161 implementation of the optional 13 character field:

S#nnnnnnVkkk

Where:

"nnnnnn is a six character sensor serial number
"kkk" is a three digit sensor firmware revision level

(12 bytes total)

3-8 SDI-12 Command and Response Protocol

H-4161

3.8 Change Sensor Address Command

The Change Sensor Address Command allows the sensor address to be changed. The address is
stored in non-volatile Flash memory within the sensor. The H-4161 will not respond if the
command was invalid, the address was out of range, or the Flash programming operation failed.

Command Response Description
"aAn! "n<cr><lf>" Change sensor address

Where:

a is the current (old) sensor address ("0-9", "A-Z", "a-z", "*", "?"). An ASCII "*"

may be used as a "wild card" address if the current address is unknown and only
one sensor is connected to the bus.

A is an upper-case ASCII character.

n is the new sensor address to be programmed ("0-9", "A-Z").

NOTE: To verify the new address use the "Identify Command."

Example of a "Change Sensor Address" command:

Command Response Description

"aA2!" "2<cr><lf>"

Change sensor address to "2"

H-4161

SDI-12 Command and Response Protocol 3-9

3.9 Extended Set_Current_Stage Command (for testing the 4-20mA output)

During installation and testing it is convenient to force set the H-4161's output to a particular
value. The “aXSCSddd” command allows the user to force the current measurement data (Stage)
to a particular setting. The H-4161 processes the ddd value using the current Max and Min
settings and updates the 4-10mA output. Both the Stage and mA output values are printed on the
LCD display. The H-4161 comes from the factory with the Max set to 20.00 and the Min to 4.00.
With these settings the value ddd is conveniently the same as what the output current (in
milliamps) will be. For example, if an “aXSCS10.0!” is issued, the output current will be

10.0mA. The data value must be between the current Max and Min settings or the output will be
clamped at 4.00mA or 20.0mA

This command is useful for testing the max and min settings over the dynamic range of your
SDI-12 sensor. For example: if Max=10.0 and Min=0.0, an “aXSCS5.0 will set the output
current to 12.0mA.

Note: if the module mode is INITIATE, the output setting will be overwritten when the H-4161
initiates a measurement on the auxSDI port.

Example of a H-4161 Extended "Set Current Stage" command:

Command Response Description

"aXSCS2.3!" "Stage_F = 2.3<cr><lf>"

Set the Stage to 2.3

3.10 Extended Set_Milliamp Command (for testing the 4-20mA output)

During installation and testing it is often convenient to force set the H-4161's output to a
particular value. The “aXSMddd” command allows the user to force the output to a particular
milliamp setting. The value is not processed with the module’s Max and Min settings. For
example: “aXSCS5.0" will set the output current to 5.0mA, regardless of the Max or Min
settings

Note: if the module mode is INITIATE, the output setting will be overwritten when the H-4161
initiates a measurement on the auxSDI port.

Example of a H-4161 Extended "Set Milliamp" command:

Command Response Description

"aXSM5.6!" "I-Out = 5.6mA<cr><lf>"

Set the output to 5.6 milliamps

3-10 SDI-12 Command and Response Protocol

H-4161

3.11 Extended Read/Write Max (High) and Read/Write Min (Low)

The H-4161 processes the captured SDI-12 data with a linear mx+b equation to scale the data
into values between 4.0 and 20.00 suitable for the 4-20mA output. The slope(m) and offset(b)
terms are automatically computed using user programmable Max and Min settings. This makes it
easy to scale the measurement data into the proper 4-20mA output. These four commands allow
the user to read or write the current Max or Min settings. The settings are stored in non-volatile
Flash memory. Once the new Max or Min value is written to the Flash memory, a copy is sent to
the sensor data buffer for verification. This data can be viewed by using a subsequent "D"
command. To verify these settings any other time, use the "XRIH" or “XRIL” commands. This
command takes 1 second to complete and places 1 value in the data buffer.

Command Response Description
"aXRIH!" “a0011<cr><lf>" Read current max (high) data setting
"aXRIL!" “a0011<cr><lf>" Read current min (low) data setting
"aXWIHddd!" “a0011<cr><lf>" Write max (high) data setting
"aXWILddd!" “a0011<cr><lf>" Write min (low) data setting

Where: a is the sensor address ("0-9", "A-Z", "a-z", "*", "?").

XRIH are upper case characters.
XRIL are upper case characters.
XWIH are upper case characters.
XWIL are upper case characters.
ddd is the new max or min value (For example: 20.0, 195)

Example of a H-4161 Extended Read High (max) command:

Command Response Time Values Description
"aXRIH!" "a0011<cr><lf>" 1 sec 1 Read Max

Command Response Description
"aD0!" "a+50.0<cr><lf>" Max is 50.0

Example of a H-4161 Extended Write High (max) command:

Command Response Time Values Description
"aXWIH1.234!" "a0011<cr><lf>" 1 sec 1 Write Max

Command Response Description
"aD0!" "a+1.234<cr><lf>" Max is 1.234

H-4161

SDI-12 Command and Response Protocol 3-11

3.12 Extended Read/Write Module Mode command

The H-4161 operates in one of two modes: MONITOR or INITIATE. When the Module Mode =
0 (monitor), the H-4161 passively monitors the communication between the data recorder and
it’s SDI-12 sensors. The H-4161 waits for, and collects a specified data parameter from a
specified sensor. The data is scaled and used to set the H-4161's 4-20mA output. When the
Module Mode =1 (initiate), the H-4161 actively initiates measurements and collects the response
from the sensor attached to the auxSDI port. The specified data parameter is scaled and used to
set the H-4161's 4-20mA output.

These two commands allow the user to examine or change the Module Mode. The H-4161 comes
from the factory with Module Mode = 0 (monitor). The Module Mode stored in non-volatile
Flash memory. Once a new value is written to the Flash memory, a copy is sent to the sensor
data buffer for verification. This setting can be viewed by using a subsequent "D" command. To
verify this setting any other time, use the "XRMM" command. This command takes 1 second to
complete and places 1 value in the data buffer.

Command Response Description
"aXRMM!" “a0011<cr><lf>" Read current module mode
"aXWMMn!" “a0011<cr><lf>" Write the module mode

Where: a is the sensor address ("0-9", "A-Z", "a-z", "*", "?").

XRMM are upper case characters.
XWMM are upper case characters.
n 0 = MONITOR, 1=INITIATE

Example of a H-4161 Extended Read Module Mode command:

Command Response Time Values Description
"aXRMM!" "a0011<cr><lf>" 1 sec 1 Read module mode

Command Response Description
"aD0!" "a+0<cr><lf>" Module Mode is MONITOR

Example of a H-4161 Extended Write Module Mode command:

Command Response Time Values Description
"aXWMM1!" "a0011<cr><lf>" 1 sec 1 Write module mode

Command Response Description
"aD0!" "a+1<cr><lf>" Module Mode is INITIATE

3-12 SDI-12 Command and Response Protocol

H-4161

3.13 Extended Set Transparent Mode command

When the Module Mode = 1 (Initiate), the H-4161 actively initiates measurements and collects
the response from the sensor attached to the auxSDI port. During setup and testing it may be
useful for the user to access the sensor attached to the auxSDI port without changing the wiring
or connectors. When activated, the Transparent mode causes the H-4161 to stop making
measurements on the auxSDI port and to make a virtual connection between the primary and
auxSDI ports. While the Transparent Mode is active, all communication to/from the H-4161's
address is passed thru to the auxSDI port. The “aM!”, “aD0!” and other internal commands of
the H-4161 are disabled and the H-4161 is essentially replaced by the sensor attached to the
auxSDI port.. The Transparent Mode is automatically deactivated when the H-4161 detects an
access to any sensor address other than its own. Note: the sensor address character of each
command is forced to “0" by the H-4161 before being forwarded to the auxSDI port.

Example of the H-4161 Extended Set Transparent Mode command:

Command Response Description
"aXSTM!" "aTransparent mode ON<cr><lf>" Transparent mode is active

H-4161

SDI-12 Command and Response Protocol 3-13

3.14 Extended Read/Write Monitored Address and Read/Write Monitored Parameter

As a data monitor, the H-4161 passively monitors the communication between the data recorder
and it’s SDI-12 sensors. The H-4161 waits for, and collects a specified data parameter from a
specified sensor. The data is scaled and used to set the H-4161's 4-20mA output. These four
commands allow the user to examine or set the sensor address and the sensor data parameter to
be monitored. At the factory the monitored address is set to “Z” and the monitored parameter is
set to “1". For example: with these settings if a data recorder collects data from sensor “Z” with
a “ZD0" command and the sensor transmits Z+123.4+24.3<cr><lf>, the value 123.4 will be
captured by the H-4161. Note: the monitored address setting is not used if Module Mode = 1
(initiate).

Do not set the Monitored Address to the same address as the H-4161's address. The address and
parameter settings are stored in non-volatile Flash memory. Once a new value is written to the
Flash memory, a copy is sent to the sensor data buffer for verification. This setting can be
viewed by using a subsequent "D" command. To verify these settings any other time, use the
"XRMA" or “XRMP” commands. This command takes 1 second to complete and places 1 value
in the data buffer.

Command Response Description
"aXRMA!" “a0011<cr><lf>" Read current monitored address
"aXRMP!" “a0011<cr><lf>" Read current monitored parameter
"aXWMAn!" “a0011<cr><lf>" Write current monitored address
"aXWMPn!" “a0011<cr><lf>" Write current monitored parameter

Where: a is the sensor address ("0-9", "A-Z", "a-z", "*", "?").

XRMA are upper case characters.
XRMP are upper case characters.
XWMA are upper case characters.
XWMP are upper case characters.
n is the new address or parameter

Example of a H-4161 Extended Read Monitored Address command:

Command Response Time Values Description
"aXRMA!" "a0011<cr><lf>" 1 sec 1 Read monitored address
Command Response Description
"aD0!" "a+Z<cr><lf>" Monitored address = Z

Example of a H-4161 Extended Write Monitored Address command:

Command Response Time Values Description
"aXWMA5!" "a0011<cr><lf>" 1 sec 1 Write monitored address
Command Response Description
"aD0!" "a+5<cr><lf>" Monitored address = 5

3-14 SDI-12 Command and Response Protocol

H-4161

3.15 Extended Read/Write AutoScan Command

When the Module Mode =1 (initiate), the H-4161 actively initiates measurements and collects the
response from the sensor attached to the auxSDI port. These two commands allow the user to
select which “M” command is sent by the H-4161 when it initiates a measurement ( “0M!”,
“0M1!”, “0M2!" etc.) . The H-4161 comes from the factory with this setting set to “0" (“0M!”).
Only the settings “0" to “9" are valid:

0 = 0M! (default)
1 = 0M1!
2 = 0M2!
3 = 0M3!
4 = 0M4!
5 = 0M5!
6 = 0M6!
7 = 0M7!
8 = 0M8!
9 = 0M9!

This setting stored in non-volatile Flash memory. Once a new value is written to the Flash
memory, a copy is sent to the sensor data buffer for verification. This setting can be viewed by
using a subsequent "D" command. To verify this setting any other time, use the "XRMC"
command. This command takes 1 second to complete and places 1 value in the data buffer.

Command Response Description
"aXRAC!" “a0011<cr><lf>" Read current AutoScan command setting
"aXWACn!" “a0011<cr><lf>" Write current AutoScan command

setting

Where: a is the sensor address ("0-9", "A-Z", "a-z", "*", "?").

XRAC are upper case characters.
XWAC are upper case characters.
n is the new parameter

Example of a H-4161 Extended Read Monitored Command command:

Command Response Time Values Description
"aXRAC!" "a0011<cr><lf>" 1 sec 1 Read AutoScan setting
Command Response Description
"aD0!" "a+0<cr><lf>" Command will be “0M!”

Example of a H-4161 Extended Write Monitored Command command:

Command Response Time Values Description
"aXWAC2!" "a0011<cr><lf>" 1 sec 1 Write AutoScan setting
Command Response Description
"aD0!" "a+2<cr><lf>" Command will be “0M2!”

H-4161

SDI-12 Command and Response Protocol 3-15

3.16 Extended Read/Write Measure Rate commands

When Module Mode = 1 (initiate), the H-4161 initiates measurements to the sensor attached to
the auxSDI port. The measurement interval is controlled by the Measure Rate setting. These
two command allows the user to examine or change the Measure Rate setting. If the Measure
Rate is set to a value less than the time it takes to make the actual measurement, measurements
will be made back-to-back, as fast as possible. At the factory the Measure Rate is set to zero.
(seconds).

The Measure Rate setting is stored in non-volatile Flash memory. Once a new value is written to
the Flash memory, a copy is sent to the sensor data buffer for verification. This setting can be
viewed by using a subsequent "D" command. To verify this setting any other time, use the
"XRMR" command. This command takes 1 second to complete and places 1 value in the data
buffer.

Command Response Description
"aXRMR!" “a0011<cr><lf>" Read current measurement rate (seconds)
"aXWMRnn!" “a0011<cr><lf>" Write measurement rate (seconds)

Where: a is the sensor address ("0-9", "A-Z", "a-z", "*", "?").

XRMR are upper case characters.
XWMR are upper case characters..
nn is the new measurement rate (seconds)

Example of a H-4161 Extended Read Measure Rate command:

Command Response Time Values Description
"aXRMR!" "a0011<cr><lf>" 1 sec 1 Read Measure Rate

Command Response Description
"aD0!" "a+0.<cr><lf>" Measure Rate =

0 seconds

Example of a H-4161 Extended Write Measure Rate command:

Command Response Time Values Description
"aXWMR5!" "a0011<cr><lf>" 1 sec 1 Write Measure Rate

Command Response Description
"aD0!" "a+5<cr><lf>" Measure Rate = 5

.0 seconds

3-16 SDI-12 Command and Response Protocol

H-4161

3.17 Extended “XTEST”

This command is used for installation and testing and requires the use of a H-4191 Sidekick
interface and a PC. This command causes the H-4161 to display a listing of the H-4161's current
settings. This is not compliant with the SDI-12 specification and is not used with data loggers.

An example of an “XTEST” printout is shown below:

H-4611 Settings:
Module Mode = MONITOR
Monitored Address = Z
Monitored Parameter = 1
AutoScan Command = 0
Measure Rate (sec)= 0
Max data (@20mA) = 20.0
Min data (@4mA) = 4.0

3.18 Extended “XHELP”

This command is used for installation and testing and requires the use of a H-4191 Sidekick
interface and a PC. This command causes the H-4161 to display a listing of the supported SDI­12 commands. This is not compliant with the SDI-12 specification and is not used with data
loggers.

H-4161

SDI-12 Command and Response Protocol 3-17

3-18 SDI-12 Command and Response Protocol

H-4161

4-20mA Current Transmitter

Type: 2-wire, loop powered
Isolation: 1000V r.m.s min
Loop Voltage: 5.5V min, 35V max
Resolution: 16-bits
Non-linearity: ±0.01% of FS max
Offset drift: ±25ppm of FS/  C max

Power Requirements

Voltage Input: 9 to 16 Volts DC
Surge Protection: Built in, 1.5 KVA
Supply Current:

Sleep mode 2.1 mA typ
Active 8.0mA typ

Appendix A

Specifications

Environmental

Operating Temperature: -20 C to +50 C
Storage Temperature: -20 C to +60 C
Hu;midity: Non condensing

Mechanical

Material: ABS plastic
Size 3.75" Long x 2.65" Wide x 1.25" Deep

Connections

+12V, SDI-12, AuxSDI: 5-position plug-in terminal strip,

Phoenix Combicon™ (provided)

SDI-12 Ports
Baud Rate: 1200
Protocol: SDI-12, 7-bit even parity, 1 stop bit
Output Voltage Levels:
Minimum high level: 3.5 volts
Maximum low level: 0.8 volts

Response Time

SDI-12 measurement sequence:

aM!: 0-seconds, 1-parameter
all other: 1, second, 1-parameter

LCD Display

Type: 2-line x 16-character, reflective
Operating Temperature: -0 C to +50 C
Storage Temperature: -20 C to +60 C

Operating Modes

Monitor: Monitor the SDI-12 port for “aD0!”

commands, update the 4-20mA output.

Initiate: Initiate measurements on the AuxSDI

port, update the 4-20ma output,
data is available via “aM!” on the
primary SDI-12 port

Transparent: SDI-12 and AuxSDI ports are connected

together

4-20mA: 2-position plug-in terminal strip,

Phoenix Combicon™ (provided)

The W

ATER

LOG® H-4161 is warranted against defects in

materials and workmanship for one year from date of shipment.

Notes

Specifications subject to change without prior notice due to
ongoing commitment to product testing and improvement.

H-4161

Specifications A-1

3-2 SDI-12 Command and Response Protocol

H-4161