CS725 Snow Water
Equivalency Sensor
Revision: 8/12
Copyright © 2010-2012
Campbell Scientific, Inc.
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Table of Contents
PDF viewers: These page numbers refer to the printed version of this document. Use the
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1. Introduction.................................................................1
2. Specifications .............................................................1
3. Wiring........................................................................... 2
4. Connecting the CS725 to a Computer ......................2
5. Terminal Setup for RS-232 Communications........... 3
6. Communicating with the CS725 ................................4
6.1 General.................................................................................................4
6.2 Auto Baud Rate Detection....................................................................4
6.3 Main CS725 Menu ...............................................................................4
6.4 Detailed Main Menu Command Information .......................................5
6.5 Hidden Commands.............................................................................17
6.6 Datalogger Talk Through Mode.........................................................17
7. Parts Overview..........................................................17
8. Site Selection Details................................................18
8.1 Collimator ..........................................................................................19
8.2 Soil Moisture Considerations .............................................................19
8.3 Obtaining Site Qualifying Counts ......................................................19
9. Mounting.................................................................... 22
9.1 Mounting Options ..............................................................................23
10. Final Parameter Setup .............................................. 25
11. Firmware Update (using command .0xw) ...............27
12. System Power Requirements and
Recommendations .................................................29
12.1 Non Solar-Powered Sites ...................................................................29
12.2 Solar-Powered Sites ...........................................................................29
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Table of Contents
13. Detailed Measurement Theory .................................29
14. Maintenance and Assembly .....................................31
15. Datalogger CRBasic Programming .........................33
15.1 Extended Data Output (.flla) Command ............................................ 33
15.2 Short Form Data Output (.fs) Command ........................................... 36
Figures
4-1. CS725 connection to DB9F-TERM .................................................... 3
7-1. CS725 components............................................................................ 18
9-1. Position of 1/4‐20 mounting holes .................................................. 23
9-2. Example of wall/plate mounting........................................................ 24
9-3. Horizontal pipe mounting shown with the 27412 Mount Kit............ 25
13-1. Gamma histogram ............................................................................. 30
14-1. CS725 main body.............................................................................. 31
14-2. CS725 inner tube shown.................................................................... 32
14-3. CS725 cutout view ............................................................................ 32
14-4. CS725 with top cap removed............................................................. 33
Tables
8-1. Collimator Guidelines ....................................................................... 19
8-2. Potassium (K) Count Range Guideline.............................................. 21
8-3. Thallium (Tl) Count Range Guideline............................................... 22
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Cautions / Safety Notes
• If you are unable to determine that your structure or mounting method is
suitable for the CS725 sensor, please contact an expert or professional who
can assist you in determining the structural mounting requirements for
your installation of the CS725.
• Always ensure that the collimator is secured to the structure with the long
safety cable.
• Do not disassemble the CS725 without consulting the factory first. The
CS725 contains a fine bead-like insulation material called Aerogel
Nanogel. The material is manufactured by Cabot Corporation. Proper
MSDS sheets and instructions should be obtained prior to opening the
CS725.
• The collimator is heavy and proper handling procedures need to be
followed when handling the part.
• Never force the connector on to the CS725. If the connector does not
easily fit into place then it is likely misaligned.
Abbreviations/Syntax
K The Element Potassium
SWE Snow Water Equivalency
Tl The Element Thallium
[] Square brackets identify a typed command. The content inside the
brackets is what is sent or typed and the brackets are excluded.
<> Denotes a special key for example <Enter> represents the Enter Key.
CS725 Snow Water Equivalency Sensor
1. Introduction
The CS725 sensor is primarily designed to measure the SWE (Snow Water
Equivalency) in a snow pack.
The CS725 obtains a measurement by passively monitoring the attenuation of
naturally existing electromagnetic radiation, due to the presence of potassium
and thallium. As snow accumulates on top of the ground, the CS725 measures
a decrease in the normal background radiation levels. The higher the water
content, the higher the attenuation of the radiation.
The CS725 has several characteristics that make it an excellent sensor for SWE
measurement applications.
• The sensor is non-contact. It is installed simply by mounting it above the
snow surface.
• The measurement is passive.
• Its performance is not affected by adverse weather conditions.
• The sensor’s measurement covers a large surface area. Typically 50 to
• It is effective with any type of snow or ice.
Proper operation of the CS725 is dependent on suitable amounts of potassium
(K) and thallium (Tl) being present in the ground. Since the radiation levels
will vary from site to site, the CS725’s performance can also be site specific.*
*No special licenses or precautions are required to install or operate the CS725.
2. Specifications
Power Requirements: 11 to 15 Vdc
Power Consumption: 180 mA
Measurement Time: Continuous, 24 hours/day
Output Format: RS-232 (1200 to 115200 bps)
Default is 9600 bps
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(538 to 1076 ft2) when mounted 3.0 m above the ground.
100 m
Measurement Range: 0 to 600 mm (0 to 23.6 in) of water equivalency
Accuracy: ±15 mm (±0.6 in) for 0 to 300 mm (0 to 11.8 in)
±15% at 300 to 600 mm (11.8 to 23.6 in)
Resolution: 1 mm (0.004 in)
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CS725 Snow Water Equivalency Sensor
Coverage Beam Angle: 60°
Operating Temperature: -40° to +40°C
Maximum Cable Length: 30 m (95 ft) (9600 bps or less)
Cable Type: 4 conductor, 2-twisted pair,
22 AWG, Santoprene jacket
Dimensions
(Without Collimator)
Length: 62 cm (24.4 in)
Diameter: 12.7 cm (5 in)
Weight
Main Body: 9.0 kg (20 lbs)
Collimator: 25 kg (55 lbs)
Total: 34 kg (75 lbs)
3. Wiring
The wiring for the CS725 connector-cable assembly is as follows:
Color Function Connection
Black Power Ground System Ground and/or RS-232 Receiver
Ground
(Pin 5 of a computer (DTE) DB-9 connector)
Red +12VDC Power Power Source
Green RS-232 (Sensor
Output)
White RS-232 (Sensor Input) Recorder/Reader RS-232 Output
Clear Shield Shield/Earth Ground
Recorder/Reader RS-232 Input
(Pin 2 of a computer (DTE) DB-9 connector)
(Pin 3 of a computer (DTE) DB-9 connector)
4. Connecting the CS725 to a Computer
The CS725 can communicate directly to PC using a terminal program such as
Hyperterminal. To provide a DB9 connection between the CS725 and a PC’s
RS-232 port, the DB9F-TERM interface PCB is used. The DB9F-TERM is
shipped with the CS725. The following diagram demonstrates how to connect
the CS725 to the DB9F-TERM.
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CS725 Snow Water Equivalency Sensor
FIGURE 4-1. CS725 connection to DB9F-TERM
When connecting the CS725 to a computer, a power source is required to
power the CS725. A good quality regulated +12 Vdc power source should be
used such as a bench power supply or a +12 Vdc battery. It is recommended to
disconnect the cable from the CS725 while terminating the cable connections.
After the connections are verified, the connector can be reconnected to the
CS725.
5. Terminal Setup for RS-232 Communications
The following are the settings required for the terminal program to
communicate with the CS725. Typical programs include Hyperterminal or
Procomm.
Baud Rate: 9600 (Default)
Data Bits: 8
Parity: None
Stop Bits: 1
Flow Control: None
Local Echo: Enabled
Terminal Mode: ANSI
Send Line Ends
with Line Feeds: Disabled
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CS725 Snow Water Equivalency Sensor
When the power is applied to the CS725 or the connector is plugged in, the
CS725 will output the following message on the RS-232 port on power up:
GMONIII Scionix 3x3 V4f_13u SN: 9999
Where:
GMONIII: Is the original sensor Identifier (now known as CS725)
Scionix 3x3: Is the Gamma Detector Type
V4f_13u: Is the Firmware Software Revision
SN: 9999 Is the sensor’s serial number
6. Communicating with the CS725
6.1 General
Immediately after power on, the CS725 will default to a baud rate defined by
the “DefaultBaudRate” parameter. This is normally 9600 bps and it is
recommended to leave the setting at 9600 bps.
The escape key resets the current command line being entered into the CS725.
If you are communicating with the CS725 using another intelligent device, the
commands should be preceded with the ESC character to ensure more reliable
operation.
The commands to the CS725 are case sensitive.
All commands are terminated by the enter key or <CR> character.
6.2 Auto Baud Rate Detection
If the terminal speed does not match the CS725’s baud rate, the startup
message will either be absent or garbled. The CS725 does support an Auto
Baud Rate Detection feature. In order to synchronize the CS725 with the
terminal, one can type the letter ‘U’ in uppercase followed by a period “.” and a
carriage return. This will trigger the auto-baud system, and the CS725 will
adjust its baud rate to the baud rate of the terminal. The period “.” followed by
a carriage return (CR) launches the Main menu once the baud rates are
synchronized.
NOTE
Any changes to the CS725 baud rate must be accounted for in
the datalogger program.
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6.3 Main CS725 Menu
The Main menu can be prompted by sending a period “.” followed by the enter
key
.<Enter>
CS725 Snow Water Equivalency Sensor
The menus can be switched between English and French. To change the
language setting, key the command .L<Enter>. This will allow the selection of
either English or French. The English version of the Main menu is as follows:
*** LIST OF COMMANDS ****
[.l] Language (French or English)
[.h] Read the current live histogram
[.hp] Display the K and Tl peak positions from the live histogram
[.hl] Display the current histogram in log scale
[.hr] Display results after completionof a manual measurement (histogram,
position and #counts K and TI).
[.e] Same as <h> command , but erases histogram at end of operation
[.a] Special command: define start/stop time limits for one measurement
[.t] Display temperature data in °C
[.d] Display date and time
[.dd] Modify date and time
[.hd] Read back histograms from EPROM according to selected dates
[.f] Read back measurement results from EPROM according to dates
[.fl] Read back the current day measurement results
[.flla] Read back last calculated line result
[.fs] Read back calculated line result in short form ? (Time and EENS
only)
[.p] Display Parameter menu
[.s] Display status and current measurement information
[.0xps] Parameters save to file function
[.0xpr] Parameters recovery from file function
[%Rhard]/[%Rboot] Restart software processor/reboot firmware
[UU] CS725/terminal synchronizing sequence for rates other than 9600 bps
6.4 Detailed Main Menu Command Information
1. [.l]
The [.l] command is used to set the language setting to either French or
English.
The following menu is activated once the [.l] command is received:
[0] Francais
[1] English
Type the number 0 for French or the number 1 for English followed by
<Enter>.
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CS725 Snow Water Equivalency Sensor
2. [.h]
The [.h] command is used to obtain the current histogram results. This
information would normally be used for diagnostics or by a user who
requires an analysis of the gamma radiation spectrum. The counts for
1024 bin values are returned in this command. The format is as follows:
12<CR><LF> This line represents the counts for BIN#1
345<CR><LF> This line represents the counts for BIN#2
333<CR><LF> This line represents the counts for BIN#3
.
.
.
30<CR><LF> This line represents the counts for BIN#1024
3. [.hp]
The [.hp] command is used to obtain the current bin positions for the Tl
and K peaks. In general the Tl peak should be near 438 and the K peak
should be near 245. It is important for the software to find the peaks
properly in order to obtain proper SWE measurements.
In most cases, the sensor must be monitoring for at least two minutes. It
may take as long as a full hour if the radiation counts are very low.
Once the command is typed, the following is immediately displayed:
This operation may take 1-2 minutes
Once the calculation has been completed, the values are displayed. Even
under ideal conditions, the values are allowed to vary from the target
values. If the value does vary by more than 30 BINS, then there may be
issues with the sensor finding the proper peaks. The displayed values are
formatted as follows:
Tl (nom = 438) K (nom = 245)
435.4 244.7
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CS725 Snow Water Equivalency Sensor
4. [.hl]
The [.hl] command is used to obtain a graphical representation of the
current histogram results. This information would normally be used for
diagnostics or by a user who requires an analysis of the gamma radiation
spectrum. The command produces a log scale graph as follows:
5. [.hr]
The [.hr] command is used to verify radiation counts in manual mode. The
[.hr] command would normally be used in the process of qualifying a site
for adequate background radiation counts and is used in conjunction with
the [.a] command. See the [.a] command for details.
Please note that the [.hr] command can take several minutes to complete.
When the command is entered, the [.hr] command will immediately report
the duration of the current manual count time as follows:
-Elapsed time,current histo : 00:03:59 (HH:MM:SS)
Wait for the calculation to complete...
There will then be a pause that can take several minutes. After the pause,
a histogram will be output followed by the radiation count summary. The
summary will report three lines; the duration of the counting, the position
of the potassium peak and its processed count value, the position of the
thallium peak and its processed count value. The output format after the
histogram is as follows:
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