Campbell CS725 User manual

INSTRUCTION MANUAL
CS725 Snow Water
Equivalent Sensor
January 2017
Copyright © 2012 - 2015
Campbell Scientific (Canada) Corp.

WARRANTY AND ASSISTANCE
This equipment is warranted by CAMPBELL SCIENTIFIC (CANADA) CORP. ("CSC") to
be free from defects in materials and workmanship under normal use and service for
twenty-four (24) months from date of shipment unless specified otherwise. *****
Batteries are not warranted. ***** CSC's obligation under this warranty is limited to
repairing or replacing (at CSC's option) defective products. The customer shall assume
all costs of removing, reinstalling, and shipping defective products to CSC. CSC will
return such products by surface carrier prepaid. This warranty shall not apply to any
CSC products which have been subjected to modification, misuse, neglect, accidents of
nature, or shipping damage. This warranty is in lieu of all other warranties, expressed or
implied, including warranties of merchantability or fitness for a particular purpose. CSC
is not liable for special, indirect, incidental, or consequential damages.
Products may not be returned without prior authorization. To obtain a Return
Merchandise Authorization (RMA), contact CAMPBELL SCIENTIFIC (CANADA) CORP.,
at [phone]. An RMA number will be issued in order to facilitate Repair Personnel
in identifying an instrument upon arrival. Please write this number clearly on the outside
of the shipping container. Include description of symptoms and all pertinent details.
CAMPBELL SCIENTIFIC (CANADA) CORP. does not accept collect calls.
Non-warranty products returned for repair should be accompanied by a purchase order to
cover repair costs.

i
Table of Contents
PDF viewers: These page numbers refer to the printed version of this document. Use the
PDF reader bookmarks tab for links to specific sections.
1. Introduction .......................................................1
1.1 Abbreviations/Syntax .............................................................................1
2. Cautionary Statements......................................2
3. Initial Inspection................................................2
4. Overview ............................................................2
5. Specifications....................................................3
6. Installation .........................................................4
6.1 Siting ......................................................................................................4
6.2 Mounting................................................................................................5
6.2.1 C2476 Collimator .........................................................................6
6.2.2 Soil Moisture ................................................................................7
6.2.3 Initial Site Evaluation ...................................................................7
6.3 Terminal Set-up for RS-232 Communications.......................................8
6.4 Communicating with the CS725.............................................................8
6.4.1 Auto BAUD Rate Detection .........................................................8
6.5 Sensor Setup...........................................................................................9
6.5.1 Set Internal Parameters for Field Deployment............................13
6.6 Final Parameter Setup...........................................................................18
6.7Final Setup Verification .......................................................................19
7. Operation .........................................................21
7.1 Internal Makeup of CS725 ...................................................................21
7.2 Power System Requirements and Recommendations...........................21
7.2.1 Solar Powered Sites....................................................................22
7.3 Wiring...................................................................................................22
7.4 Datalogger and Basic Programming.....................................................23
7.4.1 Extended data output [.flla] command........................................23
7.4.2 Short form data output [.fs] command........................................25
8. Troubleshooting and Maintenance.................27
8.1 Maintenance and Assembly..................................................................27
8.2 Firmware Update (using command .0xw)............................................27
Appendix A. Detailed Main Menu Command Information.................................................A-1
Appendix B. 24 hour K and Tl Counts used for Site Evaluation ........................................ B-1

Table of Contents
ii
Appendix C. Gravimetric Soil Moisture Method ................................................................C-1
C.1 Gravimetric Soil Moisture Method..........................................................................................C-1
C.1.1 Equipment Required .........................................................................................................C-1
C.1.2 In-field Sampling ..............................................................................................................C-1
C.1.3 Drying Samples.................................................................................................................C-1
Appendix D. FAQ ...............................................................................................................D-4
D.1 What is the calculation of height versus sampling foot print if the sensor were to be mounted at
10 m?..............................................................................................................................................D-4
D.2 Does most of the gamma detection occur under the area of the CS725?.................................D-5
Figures
FIGURE 4—1. Gamma radiation histogram.............................................................................................................3
FIGURE 6—1. CS725 with collimator and safety cable...........................................................................................5
FIGURE 6—2. Plate Mounting...............................................................................................................................6
FIGURE 6—3. CS725 with C2470 Mounting Kit.................................................................................................6
FIGURE 7—1. CS725 cross-section.......................................................................................................................21
Tables
TABLE 6-1. Collimator Guidelines ..........................................................................................................................7
TABLE 7-1. CS725 Connection to Datalogger and DB9F-TERM.........................................................................22
TABLE 8-1. Maximum BAUD Rates for Various Cable Lengths..........................................................................28
TABLE B-2. Thallium Count (Cnt Tl) Guideline for SWE – 24 hour Reading....................................................B-1
TABLE D-3. Height versus Effective Measurement in Meters.............................................................................D-4
TABLE D-4. Contribution to Total Counts versus Angle from the Center...........................................................D-5

1
CS725 Snow Water Equivalent Sensor
1. Introduction
The CS725 sensor measures Snow Water Equivalent (SWE) in a snow pack.
SWE is measured by passively monitoring the attenuation of naturally existing
electromagnetic radiation emitted from the soil or bedrock below the sensor.
This radiation is due to the presence of Potassium-40 (40K) and Thallium-208
(208Tl).
As snow accumulates, the CS725 measures a decrease in the naturally-occuring
radiation. The higher the water content of the snow pack, the higher the
attenuation of the radiation.
A collimator (available option) is used when there are sources of 40K and 208Tl
at the site that will not be covered by snow (ex: trees). The collimator acts to
reduce this radiation from affecting the measurement.
Proper operation of the CS725 is dependent on suitable amounts of 40K and
208Tl being present in the ground. Since the radiation levels will vary from site
to site, CS725 performance is site dependant.*
* No special licenses or precautions are required to install or operate the CS725
because it does not emit gamma energy.
Before using the CS725 please study:
•Section 2, Cautionary Statements
•Section 7.3, Wiring
1.1 Abbreviations/Syntax
K Potassium
SWE Snow Water Equivalent
Tl Thallium
[ ] Square brackets identify a typed command.
The content inside the brackets is what is sent
or typed; the brackets are excluded
< > Denotes a special key. For example, <Enter>
represents the Enter key.

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2. Cautionary Statements
•If you are unable to determine that your structure or mounting method is
suitable for the CS725 sensor, please contact Campbell Scientific for
assistance in determining the structural mounting requirements.
•We recommend installing this CS725 before there is snow on the ground
to establish a baseline SWE.
•Always ensure that when using a collimator, it is secured to the structure
with the safety cable provided. Due to its weight, the collimator should be
handled with caution.
•Do not disassemble the CS725 without consulting the factory. The CS725
contains a fine bead-like insulation material - Aerogel Nanogel (Cabot
Corporation). Proper MSDS sheets and instructions should be obtained
prior to opening the CS725.
•Never force the connector on to the CS725. If the connector does not
easily fit into place, it is likely misaligned.
3. Initial Inspection
•Upon receipt of the CS725, inspect the packaging and contents for
damage. File any damage claims with the shipping company. Immediately
check package contents against the shipping documentation. Contact
Campbell Scientific about any discrepancies.
•The model number and cable length are printed on a label at the
connection end of the cable. Check this information against the shipping
documents to ensure the expected product and cable length are received.
•The CS725 is shipped with a DB9F-TERM for communication, and a
safety cable.
4. Overview
The CS725 sensor is a gamma radiation spectrometer that has been specifically
designed to measure SWE. The CS725 utilizes a Thallium-doped Sodium
Iodide crystal NaI(Tl) to detect gamma radiation.
Naturally-occuring terrestrial gamma radiation is produced by traces of
radioactive elements in the earth. The most abundant of those elements are
Potassium_40 (40K) and Thallium_208 (208Tl). 40K emits gammas at 1.460
megaelectronvolts (MeV), and 208Tl at 2.613 MeV. Gamma rays have a well
defined “probability of interaction”, based on the energy of the gamma and the
nature of the material it is travelling through.
The net effect of gamma rays travelling through the snow pack, is that a
fraction of the rays interact with the snow, while another fraction is either
degraded in energy, or attenuated. Quantifying the attenuated gamma rays
provides necessary information to calculate the SWE within the CS725. As
such, the CS725 should be installed prior to snowfall to acquire a baseline

CS725 Snow Water Equivalent Sensor
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measurement and account for soil moisture, which serve as reference points
throughout the season.
Each time a gamma ray is detected by the CS725, it is placed in its
corresponding bin in the energy histogram (see Figure 4-1). This histogram is
the basic data set required for the SWE calculation. Since it is statistical in
nature, the accuracy of the SWE evaluation is proportional to the square root of
the measurement time. The CS725 builds each histogram for a 24 h period in
order to achieve the specified accuracy.
It should be noted that only the integrated counts from the 40K and 208Tl peaks
are evaluated and used to determine SWE. Recall that SWE is evaluated by
measuring attenuation by the snow pack. However, other isoptopes, such as
bismuth produced by radon decay chains, and cosmic radiation are present
above the snow pack and must be removed or accounted for when determining
SWE.
The CS725 uses an algorithm to calculate SWE. The data is held internally
until polled by a datalogger or sent to a RS-232 device. The CS725 can hold
approximately 730 days of data.
Raw Histogram sample
1
10
100
1000
10000
100000
1000000
0100 200 300 400 500 600
Energy (ADC bin units, uncalibrated)
Number of counts
40
K
208
Tl
Cosmic background
Bismuth
FIGURE 4—1. Gamma radiation histogram
5. Specifications
Features:
Compatible
Dataloggers: CR800/CR850
CR1000
CR3000

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Power requirements: 11-15 Vdc
Power Consumption: 180 mA
Measurement Time: Continuous; 24 hours/day
Output Format: RS-232 (1200 to 115200 BAUD)
Default is 9600
Measurement Range: 0 – 600 mm of water equivalent
Accuracy: ±15 mm from 0 to 300 mm
±15 % from300 to 600 mm
Resolution: 1 mm
Coverage Angle: 60° (from center)
Operating Temperature: -40°C to +40°C
Maximum Cable Length: 30 m (at 9600 BAUD or less)
Cable Type: 4 conductor
2-twisted pair
22 AWG
Stantoprene jacket
Dimensions
(w/o Collimator): Length 62 cm
Diameter 12.7 cm
Weight: Main Body: 9.0 kg (20 lbs)
Collimator (optional): 25 kg (55 lbs)
6. Installation
It is recommended to pre-configure and test the system before taking it to the
field. Issues that are unresolved before placing instrumentation in the field will
usually be more difficult to resolve.
The CS725 must be configured using a computer before deployment.
6.1 Siting
It is important to determine if the intended installation site of the CS725 will
have appropriate sources of Potassium (K) and Thallium (Tl) to provide

CS725 Snow Water Equivalent Sensor
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sufficient counts for the expected SWE. It is also important to reduce the
effects of background K and Tl sources that will adversely affect the SWE
measurement.
Do not mount the CS725 in close proximity to buildings, wood material or
trees. Wood material can contain potassium, which may be a source of gamma
radiation that will interfere with the measurements. Potassium sources above
the snow will emit gamma radiation that is not attenuated by the snow pack.
It is reasonable to have small amounts of wood material within the 6 m
clearance radius. However, be aware that reducing the amount of material near
the CS725 or increasing the distance will reduce its influence on the readings.
6.2 Mounting
Please contact a Campbell Scientific representative if you are
unsure of suitable mounting structures or methods for the CS725
• Always ensure that the collimator is secured to the structure with the long
safety cable.
• Always install the collimator after the main CS725 body is mounted and
secured to the structure.
Mount the CS725 above the snow pack. It is recommended to mount the
CS725 approximately 3 m above ground or above the expected maximum
snow height. If the CS725 is submersed in the snow, it may be damaged by
water ingress. The CS725 can also be mounted lower than 3 m; however, this
will reduce the effective measurement area.
FIGURE 6—1. CS725 with collimator and safety cable
It is possible to rotate the CS725 Main Body with respect to the mounting
plates. Figure 6-2 shows one of the four fasteners that need to be loosened in
order to rotate the main body.
Note

CS725 Snow Water Equivalent Sensor
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FIGURE 6—2. Plate Mounting
FIGURE 6—3. CS725 with C2470 Mounting Kit
6.2.1 C2476 Collimator
The collimator is optional. The collimator will help eliminate non-soil gamma
radiation sources. Factors considered when determining whether or not to use
a collimator include the presence of wooded vegetation and man-made
structures, and the expected SWE for a given site.
Table 6-1 is a guideline for determining if the site can be used with or without
a collimator.

CS725 Snow Water Equivalent Sensor
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TABLE 6-1.
Collimator Guidelines
Site Characteristics Max SWE
< 300 mm Max SWE 300 – 400 mm Max SWE > 400 mm
Very open with no proximity to
trees, buildings or vegetation
within 48 m (160 ft) radius
Optional Optional Optional
No trees, buildings or tall
vegetation within a 24 m (80 ft)
radius
Optional Optional Required
No trees, buildings or tall
vegetation within a 12 m (40 ft)
radius
Optional Required Required
Site with minimum clearance
radius of 6 m (20 ft) radius Required Required Required
6.2.2 Soil Moisture
Soil moisture can influence SWE by attenuating the signal. Avoid low lying
areas where water pools or saturates the soil during the snow melt and bog type
ground conditions due to the potentially high moisture content. It will be
necessary to determine the soil moisture (aka: soil humidity) content of the site
in % by weight. This value is entered into the CS725 setup parameters. See
Appendix C Gravimetric Soil Moisture Method for detailed instructions on
how to determine soil moisture content.
6.2.3 Initial Site Evaluation
As there is naturally-occuring variability in radiation levels from site to site, it
is recommended to qualify the site prior to permanently installing the CS725.
Required equipment:
•CS725 with accessories
•Suitable +12 Vdc power supply to run the CS725 for several hours
•Mounting hardware to vertically suspend the CS725 over the ground
at the qualifying site. Note: for qualifying purposes the suspension
height is not critical (0.5-1 m is sufficient)
•Laptop with suitable terminal emulator program (e.g. HyperTerminal)
Overview of steps:
•Mount the CS725 as close as possible to desired permanent location
•Avoid placing items underneath the CS725 during testing
•For best results, mounting at 1 m or more above the ground
•Install the collimator if available

CS725 Snow Water Equivalent Sensor
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•Connect the CS725 to the laptop and power supply, as shown in the
wiring section (7.3)
•Run the terminal emulator program you have chosen (see section 6.3)
and follow the steps to set up a CS725
•Allow the CS725 to monitor gamma radiation for 1 hour
•Review number of counts of K and Tl and compare to Table 6-2 and
6-3 to determine if site has sufficient K and Tl present in the
soil/bedrock
•If site is suitable, set CS725 parameters to determine the baseline (no
snow) SWE measurement
•24 h later, verify that the system is working properly
6.3 Terminal Set-up for RS-232 Communications
Following are 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 news feed: Disabled
6.4 Communicating with the CS725
Upon power–up, the CS725 defaults to a baud rate parameter defined by
“DefaultBaudRate”. This is normally 9600 BAUD - the recommended setting.
The ‘Esc’ key resets the current command line being entered into the CS725. If
you are communicating with the CS725 using another intelligent device, the
commands must be preceded with the Esc character to ensure reliable
operation.
All commands are terminated by the Enter key, or <CR> character.
6.4.1 Auto BAUD Rate Detection
Any changes to the CS725 baud rate must be accounted for in the
datalogger program
If the startup message is absent or garbled, or the terminal baud rate does not
match the CS725 baud rate, synchronize the baud rates by typing
‘UU’ ‘.’ <Enter>
This triggers the auto-baud system in the CS725.
Note

CS725 Snow Water Equivalent Sensor
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6.5 Sensor Setup
1. Wire the sensor to the DB9F-TERM, a +12Vdc power supply, and a PC
serial port (or USB) as shown in Table 7-1 Connection to Datalogger and
DB9F-TERM (Section 7.3).
2. Start terminal program, connect to CS725, and set internal parameters
The following example uses HyperTerminal for the terminal software.
Open HyperTerminal > File > New Connection
When the following appears, enter CS725 for the Name:
Click OK
The following screen will appear. Choose the correct COM port, which your
computer is using. Click OK

CS725 Snow Water Equivalent Sensor
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Change Port Settings as necessary to match the following screen:
Click Apply > OK
Next, go to File > Properties

CS725 Snow Water Equivalent Sensor
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Click on the Settings tab
Set parameters according to the following screen shot:
Click on ASCII Setup…

CS725 Snow Water Equivalent Sensor
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Check the box beside ‘Echo typed characters locally’
Click OK and return to the main HyperTerminal screen.
3. Apply +12Vdc power to the CS725. The sensor will power up and start
communicating with your computer.
The following screen should appear:

CS725 Snow Water Equivalent Sensor
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Where:
GMONIII: Original sensor identifier (now known as
model CS725)
Scionix 3x3: Gamma detector type
V5c_15_m: Firmware software revision
SN: 8008: sensor serial number
6.5.1 Set Internal Parameters for Field Deployment
Internal parameters are accessed by menus. There are several menu options
used for technical diagnoses and firmware upgrades; however, most are not
required for standard applications.
See Appendix A for all menu options with detailed descriptions.
Words in brackets < > are actions.
Ex: <Enter> means to hit the Enter key on your keyboard. <space> means to
hit space bar on your keyboard.
To access the Main Menu, while connected with HyperTerminal, type
<Enter>
<Enter>
? <Enter>
The following menu will appear:
English menu:
[.l] Language (French or English)
[.h] Read the current live histogram
[.hp] Display the K and Tl positions from the live histogram
[.hl] Display the current histogram in log scale
[.hr] Display results after completion of a manual measurement
(histogram, position and # counts K and Tl)
[a.] Special command: define start/stop time limits for one
measurement (manual mode only)
[.t] Display temperature in °C

CS725 Snow Water Equivalent Sensor
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[.d] Display date and time
[.dd] Modify date and time
[.hd] Read back histograms from EPROM according to dates
[.f] Read back measurement results from EPROM according to dates
[.fl] Read back current day measurement results
[flla] Read back last calculated line result
[.fs] Read back last results 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] GMON/Terminal synchronizing sequence for rates other than
9600 BAUDS
The menu will be used to:
•Set the language [.l]
•Check the internal clock [.d]
•Set current date and time [.dd]
•Display and set parameter setup menu [.p] this command includes a
submenu with parameters that must be set. See section 7.1 for
instruction
•Set start and stop times for measurement intervals [a.]
•Obtain current histogram results [h]
•Verify radiation counts in MANUAL mode [.hr]
•Display status and current measurement information [.s]
•Display current day readings [.fl]
To select a menu option, type the character found in the square
brackets followed by Enter. Ex: .d<Enter>
1. Start by setting the preferred language.
.l<Enter> {The letter l as in Lima}
[0] Tapez 0 pour Franҫais
[1] Type 1 for English
Type the required number followed by <Enter>.
More menu items can be entered successively. Type ?<Enter> to view the
menu list at any time.
2. View date and time.
.d<Enter>
Format example:
02/24/201415:00:20
dd/mm/year HR:MIN:SEC
3. Set current date and time (if required)
.dd<Enter>
Note

CS725 Snow Water Equivalent Sensor
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Modify that date? :
[1] yyyy: 2014
[2] mm: 02
[3] dd: 24
[4] hh: 15
[5] mm: 00
[6] ss: 20
[0] Exit
[99] Accept selection
To Modify: [parameter number, space, new value, CR]
Ex: 5 <space>02<Enter>
This changes the clock to 02 minutes
Type 99<Enter> for the CS725 to accept the changes
4. Verify date and time
.d<Enter>
The CS725 does not perform any timezone or Daylight-Savings time
correction.
5. Enter parameter setup menu
.p<Enter>
The following menu will appear:
[1] Station ID (Max 8 characters; ex: Gouin_21) ............ : _SWESite1
[3] Time of start of measure (relative to GMON 00h RTC)..... : 00
[4] Delay after start of measure for data transmission (secs.)
0=> No transmission).. : 0
[5] Frequency of data transmission: 0 => every 24 h
1 => every 6 h .. : 1
[6] GMON height above ground in centimeters................. : 300
[7] Observed position for the K line on the histogram....... : 245
[8] Collim (1: Collimator installed; 0: no collimator)...... : 1
[9] Nominal soil humidity in %weight,(min: 1, max: 150)..... : 25
[10] Estimated soil humidity in %weight (min: 1, max: 150)
for HCalib mode.. : 27
[11] NoK..................................................... : 230000
[12] NooK (residual K counting) Default:0 ................... : 0
[13] N0Tl.................................................... : 41000
[14] n00Tl ( residual Tl counting).......................... : 0
[16] SN Threshold for the snow cover........................ : 0
[17] Baud rate for scheduled transmissions................... : 9600
[18] Number of hours per partial histo (hours),(1,2,3,or 6) : 1
[19] Manual mode (1); Auto mode (0) ; HCalib mode (2);...... : 1
[0] Quit without saving the new parameters on EPROM
[99] Save parameters on EPROM
To modify: [parameter number, space, new value,CR]
=>
6. Set Station ID 1<space>user defined<Enter>
Maximum 8 alphanumeric characters; no spaces.
99 <Enter> this saves the parameter to the CS725
99<Enter> must be entered twice