Xylem H-424MS User Manual

Model

H-424MS

Spread Spectrum

SDI-12 Radio Bridge

Owner's Manual

Version 1.1

(for system revision “C” or higher)

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.

3. DUTIES OF YOU, THE USER

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

(a) USER agrees that they will not remove from the exterior of the housing of the PRODUCT any

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

(b) USER agrees that they shall not disassemble or otherwise reverse engineer the PRODUCT.

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

their own confidential and proprietary information.

4. TERM

USER may enjoy these rights only as long as their possession of the PRODUCT shall continue to be
rightful. These rights will cease if the PRODUCT is returned to DESIGN ANALYSIS under the terms of
any redemption offer, warranty, or money-back guarantee, or if USER transfers the PRODUCT to
another party on terms inconsistent with this agreement.

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-4271

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
same within a reasonable period of time. In the event that DESIGN ANALYSIS is unable to
make the necessary repairs or replacement within a reasonable period of time, the original
purchase price will be refunded upon the return of the PRODUCT to DESIGN ANALYSIS.

(d) Limitations

(i) THE ENTIRE REMEDY FOR BREACH OF THIS LIMITED WARRANTY SHALL

BE LIMITED TO REPLACEMENT OF THE DEFECTIVE PRODUCT OR
REFUNDING OF THE PURCHASE PRICE, AS SET FORTH ABOVE. IN NO
EVENT WILL THE LIABILITY OF DESIGN ANALYSIS TO USER OR TO ANY
OTHER PARTY EXCEED THE ORIGINAL PURCHASE PRICE OF THE PRODUCT,
REGARDLESS OF THE FORM OF THE CLAIM.

(ii) EXCEPT FOR THE EXPRESS WARRANTIES ABOVE, DESIGN ANALYSIS

SPECIFICALLY DISCLAIMS ALL OTHER WARRANTIES, INCLUDING,
WITHOUT LIMITATION, ALL IMPLIED WARRANTIES OF MERCHANTABILITY
AND FITNESS FOR A PARTICULAR PURPOSE.

(iii) UNDER NO CIRCUMSTANCES WILL DESIGN ANALYSIS BE LIABLE FOR

SPECIAL, INCIDENTAL, CONSEQUENTIAL, INDIRECT, OR ANY OTHER
DAMAGES OR CLAIMS ARISING FROM THE USE OF THIS PRODUCT, THIS
INCLUDES LOSS OF PROFITS OR ANY OTHER COMMERCIAL DAMAGES,
EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. IN NO EVENT
WILL DESIGN ANALYSIS BE LIABLE FOR ANY CLAIMS, LIABILITY, OR
DAMAGES ARISING FROM MODIFICATION MADE THEREIN, OTHER THAN
BY DESIGN ANALYSIS.

(iv) THIS LIMITED WARRANTY GIVES USER SPECIFIC LEGAL RIGHTS. USER

MAY ALSO HAVE OTHER RIGHTS WHICH VARY FROM STATE TO STATE.
SOME STATES DO NOT ALLOW LIMITATIONS ON HOW LONG AN IMPLIED
WARRANTY LASTS OR THE EXCLUSION OF INCIDENTAL OR
CONSEQUENTIAL DAMAGES, SO THOSE LIMITATIONS OR EXCLUSIONS
MAY NOT APPLY.

6. GOVERNING LAW

This Agreement and its validity and interpretation shall be governed by the laws of the State of Utah,
notwithstanding any choice of law rules of Utah or any other state or jurisdiction.

W-2 User Agreement/W

ATER

LOG® Warranty

H-4271

1.1 Introduction

Chapter 1

Operation

The W
use and works with any SDI-12 data recorder. The radio link provides transparent, SDI-12
compliant communication between your data recorder and one or more remote sites. All SDI-12
commands are supported, including manufacturer specific extended commands.

Two or more H-424MS modules are required; one connected to the data recorder (master) and
one located at each remote site (slaves). Each remote site can have multiple SDI-12 sensors.
The master and slave H-424MS modules are identical, a user accessible circuit board jumper
determines whether the H-424MS operates as a master or slave.

The radio link uses modern frequency hopping spread spectrum telemetry radios. Spread
spectrum technology is highly secure and has good interference immunity. The radio operates in
the license-free, 900 Mhz ISM Band eliminating the need for any FCC licensing.

The radio system has an optional power-save feature which allows operation with less than 2mA
of average standby battery current.

1.2 Operation

Each H-424MS contains a small microprocessor and a spread spectrum telemetry radio. The
microprocessor buffers commands and data between the SDI-12 port and the radio. All SDI-12
compliant commands will work, including manufacturer specific extended commands. Note
however, your data logger must support SDI-12 compliant “retries” to work with the H-424MS.
Most data loggers support retries while logging but certain models do not provide retries for
transparent commands. Transparent SDI-12 commands will not work with these data loggers.

ATER

LOG® H-424MS is a spread spectrum SDI-12 radio bridge. The radio link is easy to

A circuit board jumper selects either full power or power-save operation. When jumpered for
full power operation, each H-424MS draws approximately 100mA continuous. The full power
mode has the advantage of providing completely transparent SDI-12 communication with no
waiting for the remote sites to power-up.

Unfortunately, for power save operation the SDI-12 protocol has no handshake mechanism for
delaying the timing of the sensor response. This makes it difficult to implement a radio link
which has remote stations operating in a low power sleep mode. When operated in the power
save mode, the H-424MS radio link uses the wakeup scheme described in the next section.

H-424MS

Operation 1-1

Normally the H-424MS operates as a transparent SDI-12 to SDI-12 bridge. However, in order to
wake the remote end of the link from sleep the master H-424MS can be addressed itself as a
“sensor”. The H-424MS comes from the factory with its address set to “0". When the master H­424MS detects address 0 it responds as a SDI-12 sensor and does not pass the command to the
remote site(s). Issuing the “0M!” command causes the H-424MS to perform a wakeup sequence
to the remote sites. The timing is controlled by two timers; a Wakeup and an Inactivity timer.
The settings of these programable timers is stored in EEPROM within the H-424MS;

Power Save Operating Sequence

1. The data recorder first issues a “0M!” command to the master H-424MS module.

2. The master H-424MS responds to the command as a pseudo “sensor”, and reports the
measurement will take a fixed period of time to complete. The reported time is
determined by the Wakeup Interval time setting + 1 seconds.

3. The master H-424MS transmits wakeup nulls every 40usec during the “measurement”.

4. Remote H-424MS modules periodically wake up and check for inbound messages. The
wake up is initiated by a low power circuit controlled by the Wakeup Interval setting.

5. If an inbound message is detected while awake, the remote module remains awake for a
period set by the Inactivity Timer.

6. At the completion of the “0M!” command, both the master and slave H-424MS modules
are awake and can service a SDI-12 command. At this point the data logger issues
measurement or other commands to the actual remote sensors.

7. If no additional commands are sent by the data logger, both master and remote modules
resume their low power sleep mode after their respective Inactivity Timers run down.

1.3 Setting the Jumpers

The H-424MS circuit board has three push-on jumpers which must be properly set. Each jumper
is a 3-pin stake-pin header with two possible positions. The jumpers can be accessed by opening
the front cover of the enclosure.

Jumper Function Options Description

J2 Mode Master/Slave Selects either Master or Slave operation
J3 Power Save On/Off Enables or disables the power save feature
J6 Loopback Test On/Off Enables or disables the loopback test mode

All H-424MS's in the installation MUST have the same power-save jumper selection. Leave the
Loopback Test jumper in the OFF position for normal operation.

1-2 Operation

H-424MS

1.4 Programming Your Data Recorder

You must prepare your data recorder to receive and record SDI-12 data from the sensors
attached to the data recorder. Since data recorders differ widely, refer to your recorder
manufacturer's directions.

If you are not using the H-424MS power save feature (power save jumpers are set to OFF), no
additional programming of the data recorder is needed. The SDI-12 radio link will operate
transparent to the data recorder’s operation. Do not set the address of any remote sensor to “0".

If you are using the H-424MS power save feature (power save jumpers set to ON), you will need
to program your data recorder to collect one data value from the local H-424MS with a “0M!”
command. The H-424MS's address can be changed if necessary (see Chapter 2). The dummy data
value collected can be discarded. The data recorder must make this “measurement” BEFORE
attempting to access any sensor located on the remote end of the radio bridge. The purpose of this
pseudo measurement is to allow built-in time to wake the remote sites from sleep. The H-424MS
will send a normal service request at the completion of the “measurement”.

Your data logger allows you to select which SDI-12 addresses which will be logged, but certain
models do not allow the address sequence to be specified. Often the logger will start at the lowest
selected address and automatically sequence to increasing addresses. You must change the
address of your sensors or of the H-424MS such that the H-424MS's “pseudo” sensor is always
accessed first. The H-424MS comes from the factory with its address set to “0" which will work
for most installations.

1.5 Programming the H-424MS Power Save Settings

When the power save option is not selected, the radios are continually powered, normally in a
receive mode drawing 135mA. In order to reduce the power draw use the power save mode. If
the power save option is selected, the radios are normally turned off, reducing the standby power
draw to 0.5mA. Periodically the slave H-424MS wakes up from the low power mode, turns the
radio on and listens for messages from the master. The Wake Interval value determines how
often this occurs. The default Wake Interval is 15 seconds. The slave listens for 170ms, if no
messages are found it returns to the sleep condition. The Wake Interval setting determines the
average current draw, for this example the slave draws 0.5mA for 15 seconds and 135mA for
170ms. A shorter Wake Interval setting allows faster completion of the “0M!” command at the
cost of higher average current drain.

The master H-424MS remains in the 0.5mA low power mode until the data logger issues a break.
After receiving the “0M!” command the radio is turned on, requiring 135mA. If no SDI-12
activity is detected over a period of time controlled by the Inactivity Timer setting, the radio is
turned off and the master resumes it’s 0.5mA low power mode. The default Inactivity Timer is 30
seconds.

H-424MS

Operation 1-3

The H-424MS modules comes from the factory with the following settings:

SDI Address: 0
Wakeup Interval: 15 Seconds
Inactivity Timer: 30 Seconds

These settings should work for most applications, these values provide a good compromise
between low power operation and system responsiveness. Both Master and Slave H-424MS
modules must be programmed with the SAME timer settings. The programmed timer settings of
the Master module can be observed or changed with extended commands addressed to sensor “0"
(see Chapter 2 for details). The settings of the remote (slave) module cannot be accessed
remotely. To observe or change the timer settings of a remote module the module must be
temporarily removed from service, jumpered as a master, and connected directly to the data
recorder as a local “sensor”. After programming, the module must be jumpered as a slave again
and returned to service at the remote site.

1.6 Connecting The Antenna

The H-424MS may be used with a 50-ohm, 900 Mhz antenna providing the effective radiated
power is 6dB or less. The antenna connector is a reverse type-TNC connector which is required
to meet FCC part 15.203 regulations. A simple vertical whip antenna will work up to 2 or 3
miles. Longer distances require a directional antenna with gain. A 6dB or 9dB YAGI will work
fine, do not use a 12dB model. At 900 MHz, RG58 type coaxial antenna feed lines have
excessive loss (1.8dB/10 feet). Consider using newer low loss RF cable such as Times
Microwave LMR-400 or similar (0.8dB/10 feet). The LMR-400 requires special RG8
connectors.

The H-424MS is packaged in a weather tight enclosure and is best mounted as close to the
antenna as possible. The H-424MS has a ground lug which should be connected to a good earth
ground with a heavy copper wire. The ground helps provides lightning protection for the radio,
your sensors and the data logger.

The H-424MS radios all operate at the same frequency. If multiple data logger sites are deployed,
make certain the radios of each separate logging site cannot “hear” each other. The radios can be
ordered with alternate frequencies, please contact the factory for further information.

1-4 Operation

H-424MS

1.7 Making SDI-12 Connections

The H-424MS enclosure has a 4-pin SDI-12 connector. The power for the H-424MS and the
radio is supplied by the SDI-12 +12V input. Table 1 shows the proper connections. Refer to the
wiring diagram printed on the H-424MS's product label for the connector pinout.

SDI-12 Connector

Pin Name Wire Color

1
2
3
4

Words of caution:

! Even though the H-424MS operates in a low power mode, the transmitter requires 800mA

for short bursts. Make certain your wiring and battery is capable of supplying sufficient
current .

! Keep the lead wires as short as possible.
! Use shielded cables in noisy environments.
! Connect the ground post to a good earth ground.

1.8 Troubleshooting

The H-424MS circuit board has a red LED indicator which is lighted when the radio is powered.
After installing the H-424MS's, antennas and wiring; make the following tests:

1.8.1 Testing With Power Save Jumpers = OFF:

+12Volt DC
SDI-12 Data
Ground
Ground

Red
White
Black
Shield

The LED indicators in both master and slave should be continually illuminated. Using the
transparent mode of your data logger issue a “0I!" command. The master H-424MS should
respond with a SDI-12 identification string. Issue a command to your remote SDI-12 sensor.
Check for the correct response.

1.8.2 Testing With Power Save Jumpers = ON:

The LED indicator in the slave should blink every 15 seconds. If you have changed the Wake
Interval setting, the LED should blink at your chosen interval. The LED indicator in the master
should be OFF. Using the transparent mode of your data logger, issue a “0I!" command. The
master H-424MS should respond with a SDI-12 identification string. Issue a “0M!” command,
the H-424MS should respond with “00161<cr><lf>” and the LED in the master should light.
The next time the slave powers up its radio, the slave should detect inbound messages and

H-424MS

Operation 1-5

remain on for 30 seconds. Before the 30 second inactivity time elapses, issue a “aM!” or other
command to your sensor and check for proper response. After 30 seconds of inactivity, the LED
indicators on both master and slave modules should go out indicating the inactivity timers have
powered down the radios.

1.8.3 Troubleshooting The Radios:

If the above tests fail, the problem may be in the radio or antenna system. The radios are difficult
to field test when operating with the SDI-12 protocol due to the short bursts of data. The radio
system can be more easily tested with the aid of a lap-top computer or RS-232 terminal. With
the following setup you can transmit ASCII messages or other test data while testing or aligning
the antennas. The radio link is tested by connecting a computer terminal to one radio and
jumpering the other radio for Loopback Test operation. With this test, one person can test both
up-link and down-link communication paths.

The radios have a standard RS-232C interface which operates at 9600 baud. For hand typed
ASCII text or bursts less than 40 bytes, no special handshaking is needed. To prevent the system
from turning the radio power off, jumper both H424's for Power Save = OFF. On one of the
radios, unplug the ribbon cable between the radio and the control board. You will need to
remove the four screws holding the radio to the backplate to access the 9-pin RS-232 connector
on the radio. The radios have a female DB9 connector, pin-2 is received data output and pin-3 is
transmit data input. With a standard 9-pin RS-232 cable, connect the radio to a laptop computer
or terminal. Leave the cable to the control board disconnected. If you are using a computer, use a
terminal program such as XTALK or PROCOMM to communicate with the radio. Make sure
your computer or terminal is set for full-duplex, 9600 Baud. The other radio in the link to be
tested must be programmed for “loopback test” operation. Do this by setting the Loopback Test
jumper of the remote radio to the ON position.

Test the radio link by typing characters and checking for the proper echoed response. As you
type, the characters are transmitted to the remote station then re-transmitted back to the local
station and displayed on your screen. Both up-link and down-link paths are tested at the same
time.

1-6 Operation

H-424MS

1.9 FCC Restrictions

This equipment has been tested and found to comply with the limits for a Class B digital device,
pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection
against harmful interference in a residential installation. This equipment generates, uses, and can
radiate radio frequency energy and, if not installed and used in accordance with the instructions,
may cause harmful interference to radio communications. However, there is no guarantee that
interference will not occur in a particular installation. If this equipment does cause harmful
interference to radio or television reception, which can be determined by turning the equipment
off and on, the user is encouraged to try to correct the interference by one or more of the
following measures:

! Reorient or relocate the receiving antenna.
! Increase the separation between the equipment and receiver.
! Connect the equipment into an outlet on a circuit different from that to which the receiver is

connected.

! Consult the dealer or an experienced radio/TV technician for help

1.10 Agency Certifications

The 9XStream RF module complies with Part 15 of the FCC rules and regulations. Compliance
with the labeling requirements, FCC notices and antenna usage guidelines is required by the
system integrator. The 9XStream module may only be used with antennas that have been tested
an approved for use with this module.

H-424MS

Operation 1-7

1-8 Operation

H-424MS

Chapter 2

SDI-12 Command and Response Protocol

2.1 SDI-12 Command and Response Protocol

Normally the H-424MS operates as a transparent SDI-12 to SDI-12 bridge. However, in order to
wake the remote end of the link from sleep the master H-424MS can be addressed itself as a
“sensor”. The H-424MS comes from the factory with its address set to “0". When the master H­424MS detects address 0 it responds as a SDI-12 sensor and does not pass the command to the
remote site(s). Issuing the “0M!” command causes the H-424MS to perform a wakeup sequence
to the remote sites. In addition, address 0 allows the Wakeup and Inactivity Timer settings of the
H-424MS link to be observed or modified.

The following is a brief description of the Serial Digital Interface (SDI-12) Command and
Response protocol used by the W
description of the commands and data format supported by the H-424MS.

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.

ATER

LOG® Series Model H-424MS “sensor”. Included is a

During normal communication, the data recorder sends an address together with a command to
the H-424MS. The H-424MS 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:

"0-9", "A-Z", "a-z", "*", "?". The H-424MS will be initially programmed at
the factory with the address of "9". Addresses "0 to 8" 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 remote

sensor, regardless of its actual address.
"!" 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.

Notes:

# 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-424MS

SDI-12 Command and Response Protocol 2-1

2.2 Measure Command

The H-424MS Measure Command causes the H-424MS to wake the remote site(s) from low
power sleep. The time required to complete this process is the Wake Interval setting plus 1­second. During this period the H-424MS transmits wakeup nulls which are detected by the
remote site(s) when they periodically wake and check for activity. To be SDI-12 compliant a
dummy data value is 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>" is 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 anytime after the service request is received or the specified processing time has
elapsed.

Example of a H-424MS "aM!" command:

Command Response Time Values Description

------------- --------------------- ------- -------- -------------------------------

"aM!" "a0161<cr><lf>"

Subsequent Command Response

--------------------------- ------------------------------------

"aD0" a+1<cr><lf>

Where:
1 = Fixed dummy “data”.

16 sec 1 Wakeup the remote stations

2-2 SDI-12 Command and Response Protocol

H-424MS

2.3 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!" through "aD9!" "apd.d ... pd.d<cr><lf>"

Where:

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

D0..D9 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 one or more values were specified and a "aD0!" returns no data (a<CR><LF> only), it means
that the measurement was aborted and a new "M" command must be sent.

H-424MS

SDI-12 Command and Response Protocol 2-3

2.4 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 H-424MS "aV!" command:

Command Response Time Values Description

------------- --------------------- ------- -------- ---------------------------

"aV!" "a0013<cr><lf>"

Subsequent Command Response

--------------------------- --------------------------------------------

"aD0" a+123.456+78.9+y<cr><lf>

Key Description Units

------------- ------------------------- ---------------------------­ +123.456 Fixed test data
+78.9 Fixed test data
y ROM checksum test 0 = Failed, 1 = Passed

1 sec 3 Return fixed data and diagnostic

data for testing purposes.

2-4 SDI-12 Command and Response Protocol

H-424MS

2.5 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", "*", "?").

2.6 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.

H-424MS

SDI-12 Command and Response Protocol 2-5

Example of a H-424MS "aI!" command:

"a12 DAA H-424vvvS#nnnnnnVkkk<cr><lf>"

H-424MS 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

2.7 Change Sensor Address

The Change Sensor Address Command allows the sensor address to be changed. The address is
stored in non-volatile EEPROM within the sensor. The H-424MS will not respond if the
command was invalid, the address was out of range, or the EEPROM programming operation
failed.

Command Response Description

------------- ------------------------- --------------------------­"aAn!" "n<cr><lf>" Change sensor address

(12 bytes total)

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", "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"

2-6 SDI-12 Command and Response Protocol

H-424MS

2.8 Read Wake Interval and Read Inactivity Timer Commands

The Wake Interval and Inactivity Timer values control the H-424MS's power save operation.
These values can be read by the SDI-12 host with the following commands. Note only the
settings of the H-424MS which is jumpered for “Master” operation can be read.

The default values are:

Wake Interval: 15 Seconds
Inactivity Timer: 30 Seconds

Command Response Description

------------- ------------------------- -----------------------------

"aXRW!" "a0011<cr><lf>" Read Wake Interval (seconds)
"aXRI!" "a0011<cr><lf>" Read Inactivity Timer (seconds)

Where:

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

XRW are upper case characters.
XRI are upper case characters.

This command takes 001 seconds to complete and places 1 value in the data buffer. Use the
“aD0" command to collect and view the value.

Example of a H-424MS Extended "Read Wake Interval" command:

Command Response Time Values Description

------------------- ------------------------ ------ --------- -----------------------------

"aXRW!" "a0011<cr><lf>"

Command Response Description

------------------- ------------------------ -----------------------------

"aD0!" "a+15.<cr><lf>"

1 sec 1 Read Value

Wake Interval is 15 seconds

H-424MS

SDI-12 Command and Response Protocol 2-7

2.9 Write Wake Interval and Write Inactivity Timer Commands

The Wake Interval and Inactivity Timer values control the H-424MS's power save operation.
These values can be written by the SDI-12 host with the following commands. Note only the
settings of the H-424MS which is jumpered for “Master” operation can be accessed.

These commands allows the user to write (change) the timer values. The new value is stored in
non-volatile EEPROM within the H-424MS. Once the new timer value is written to the
EEPROM, a copy is sent to the sensor data buffer for verification. This data can be viewed by
using a subsequent "D" command. To observe the timer settings any other time, use the "Read
Wake Interval" or “Read Inactivity Timer” commands.

Command Response Description

------------- ------------------------- -----------------------------

"aXWWddd!" "a0011<cr><lf>" Write Wake Interval
"aXWIddd!" "a0011<cr><lf>" Write Inactivity Timer

Where:

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

XWW are upper case characters.
XWI are upper case characters.

ddd is the new timer value. Valid settings are from 1 to 255 seconds.

The input format is very flexible. Some examples are shown below.

20.0
10

255.0

Example of a H-424MS Extended "Write Wakeup Interval" command:

Command Response Time Values Description

------------------- ------------------------ ------ --------- -----------------------------

"aXWI20!" "a0011<cr><lf>"

Command Response Description

------------------- ------------------------ ----------------------------

"aD0!" "a+20.<cr><lf>"

1 sec 1 Write Timer Setting

Timer verified at 20.0 seconds

2-8 SDI-12 Command and Response Protocol

H-424MS

Appendix A

Specifications

Protocol

Local: SDI-12
Remote: SDI-12
Type: Transparent SDI-12.

Works with all SDI-12
commands including extended
and V1.2 commands.

Requirements: Data logger must support

multiple (3/3) SDI-12
breaks with retries.

Radio

Frequency Range: 902 to 928 Mhz
Line of Sight: 7 plus miles - depending on

antenna and site conditions.

Modulation Type: Frequency Hopping Spread

Spectrum
RF Connector: Reverse Type-TNC
Transmit Power: 100 mW (20 dBm)
Receive Sensitivity: -110 dBm

SDI-12 Output

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

Environmental

Operating Temperature: -40 to 60EC
Storage Temperature: -50 to 70EC
Humidity: 0 to 100%

Mechanical

Enclosure: Fiberglass, NEMA 4
Size: 8.00 x 6.00 x 4.00 in.

W/ hinged screw cover

Connector
H-424-MS: Switchcraft EN3P4M

(4-pin male)

Mate: Switchcraft EN3C4F

(4-pin female)

Warranty

The W

ATER

LOG® H-424MS is warranted against

defects in materials and workmanship for one year
from date of shipment.

Power Requirements

Voltage Input: 9.6 to 18.0 Volts DC

Power Control: Remote station uses

programable sleep/wakeup to

detect carrier.
Current:
Standby: 510ua (sleep)

Receive: 135 mA
Transmit: 800 mA
Average w/
power control: Less than 2.0mA

H-424MS

Specifications A-1

2-2 SDI-12 Command and Response Protocol

H-424MS