Campbell CS241 User manual

Revision: 05/2021
Copyright © 2020 – 2021
Campbell Scientific, Inc.

Table of contents
1. Introduction 1
2. Precautions 1
3. Initial inspection 1
4. QuickStart 2
5. Overview 4
6. Specifications 6
7. Installation 7
7.1 Circuit diagrams 8
7.2 Wiring 9
7.3 Data logger programming 11
7.3.1 Resistance measurement and conversion to temperature 12
7.4 Placement on a photovoltaic (PV) module 13
7.5 Mounting/cable strain relief 13
7.5.1 Adhesive mounting strip 13
7.5.2 Cable strain relief 13
7.5.3 Extreme sealing tape 15
7.6 Cable resistance/long cable lengths 16
7.7 Electrical noisy environments 17
8. Maintenance and troubleshooting 18
8.1 Maintenance 18
8.2 Troubleshooting 18
Appendix A. Importing Short Cut code into CRBasic Editor 19
Appendix B. Sensor material properties 20
B.1 3M F9473PC adhesive 20
Table of Contents - i

1. Introduction
The CS241 temperature sensor uses a precision 1000 ohm Class A platinum resistance
thermometer (PRT) to measure temperature. It is designed for measuring the back-of-
photovoltaic (PV) module temperature but also can be used to measure the surface temperature
of other devices. The CS241 can be measured with a 2-wire or 4-wire configuration and is
compatible with most Campbell Scientific data loggers.
NOTE:
This manual provides information only for CRBasic data loggers. The sensor is also
compatible with our retired Edlog data loggers. For Edlog data logger support, contact
Campbell Scientific. Support for Edlog data loggers is no longer free; see
www.campbellsci.com/news-edlog-retiring for more information.
2. Precautions
lREAD AND UNDERSTAND the Safety section at the back of this manual.
lDo not use epoxy to secure the sensor head to a PV module.
lBefore mounting, the installers need to wash their hands and then clean the back of the PV
module or other device using the isopropyl alcohol pad shipped with the sensor.
lPrying the sensor head off will likely damage both the sensor and PV module.
lProper strain relief of the cable is required after mounting the sensor to the measurement
surface (Mounting/cable strain relief (p. 13)).
lPlacement of the cable inside a rugged conduit is advisable for cable runs over 4.5 m (15 ft),
especially in locations subject to digging, mowing, traffic, power tools, animals, or lightning
strikes.
3. Initial inspection
lUpon receipt of the sensor, inspect the packaging and contents for damage. File damage
claims with the shipping company.
CS241 PT-1000 Class A, Back-of-Module Temperature Sensor1

lThe model number, cable length, and cable resistance 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 were received.
4. QuickStart
A video that describes data logger programming using Short Cut is available at:
www.campbellsci.com/videos/cr1000x-data logger-getting-started-program-part-3 . Short
Cut is an easy way to program your data logger to measure the sensor and assign data logger
wiring terminals. Short Cut is available as a download on www.campbellsci.com . It is included
in installations of LoggerNet, RTDAQ, or PC400.
The following procedure also shows using Short Cut to program the CS241.
1. Open Short Cut and click Create New Program.
2. Double-click the data logger model.
3. In the Available Sensors and Devices box, type CS241. You can also locate the sensor in the
Sensors > Temperature folder. Double click the sensor model. The surface temperature
defaults to degree C. This can be changed by clicking the Temperature box and selecting
one of the other options. If using the 2-wire configuration, type the Cable Resistance. This
value is unique for each sensor, and is printed on the heat shrink label attached to the
sensor cable.
CS241 PT-1000 Class A, Back-of-Module Temperature Sensor2

4. Click on the Wiring tab to see how the sensor is to be wired to the data logger. Click OK
after wiring the sensor.
5. Repeat steps three and four for other sensors you want to measure. Click Next.
6. In Output Setup, type the scan rate, a meaningful table name, and the Data Output Storage
Interval.
CS241 PT-1000 Class A, Back-of-Module Temperature Sensor3

7. Select the measurement and its associated output option.
8. Click Finish and save the program. Send the program just created to the data logger if the
data logger is connected to the computer.
9. If the sensor is connected to the data logger, check the output of the sensor in the data
logger support software data display in LoggerNet, RTDAQ, or PC400 to make sure it is
making reasonable measurements.
5. Overview
The CS241 is a surface mountable platinum resistive thermometer (PRT) that measures back-of-
module temperature for solar energy applications. It uses a precision PT-1000 Class A PRT to
provide the highest level of accuracy. To withstand the harsh treatment that commonly occurs
with meteorological station installation, the sensing element is safely housed inside a specially
designed self-adhesive aluminum disk (FIGURE 5-1 (p. 5)).
The disk protects the PRT, particularly during installation, and promotes heat transfer from the
surface. An adhesive tab on the disk fastens the sensor to the measurement surface.
The CS241 provides PV stakeholders with highly accurate back-of-module temperature, even at
long cable lengths, in power performance modeling and simulation of solar energy applications.
Back-of-module temperature is critical for any evaluation of effective irradiance and power
conversion.
CS241 PT-1000 Class A, Back-of-Module Temperature Sensor4

FIGURE 5-1. CS241 temperature sensor
Benefits and features:
lDesigned for optimal performance on bifacial PV module
lEasy installation with maximum sensor-to-module bonding strength and smaller profile
lNIST-traceable, serialized calibration certificate supplied with every sensor
lMeets or exceeds IEC 61724 Class A performance specifications
lPrecision PT-1000 Class A sensing element
lCompliant with IEC 60751, DIN EN 60751 (according to IEC 751)
lSuitable for use on floating PV arrays
lSlim design to minimize sensor impact on bifaciality (<2% of full-size cell area)
lThermal conductance greater than 600 W/(m2 K)
lMaximum sensor-to-module bonding
lHigh temperature rating to 150 °C
lUser-selectable and standard cable lengths offered
l2-wire or 4-wire configurations to satisfy accuracy even at long cable lengths
lCompatible with Campbell Scientific CRBasic data loggers: CR6, CR3000, CR1000X, CR800
series, CR300 series, CR1000
CS241 PT-1000 Class A, Back-of-Module Temperature Sensor5

6. Specifications
Sensor: Precision 1000 ohm Class A platinum sensing element
Class A sensor accuracy: ± (0.15 + 0.002t) °C
Operating temperature range: –40 to 150 °C
Temperature coefficient: TCR = 3850 ppm/K
Long-term stability: Maximum R0 drift = 0.04% after 1000 hours at 400 °C
Measuring current: 0.1 to 0.3 mA
Temperature uncertainty: ±(0.3 to 0.4 °C) for the –40 to 100 °C measurement range
when using the CR1000X data logger
Disk diameter: 2.54 cm (1.0 in)
Height: 0.419 cm (0.165 in)
Disk material: Anodized aluminum
Weight: ~27 g (0.06 lb) with 1 m (3 ft) cable
Approvals: Conforms with the Restriction of Hazardous Substances
Directive (RoHS2)
Compliance: View compliance documents at:
www.campbellsci.com/cs241
 Meets or exceeds IEC 61724 Class A performance
specifications
Industrial standards: Compliant with IEC 60751, DIN EN 60751,
Industrial Design (IEC Class 4) (according to IEC 751)
IP rating: IP68 rating (self certified): 1 m (3 ft) submersion for 90
minutes
EMC compliance: Conforms with Electromagnetic Compatibility Directive
(EMC)
RoHS2: Conforms with Restriction of Hazardous Substances
Directive (RoHS2)
POE compliance: POE compliant (802.3af) to 100 meters when installed per
recommendations in TIA TSB-184
CS241 PT-1000 Class A, Back-of-Module Temperature Sensor6

CAT5e: Cable will meet CAT5e channel requirements to 100 meter
length
Sensor cable (sensor head-to-M12 connector)
Cable diameter: 0.216 cm (0.085 in)
Cable length: 0.9 m (3 ft)
Jacket material: White semi-gloss perfluoroalkoxy (PFA), insulated
Jacket rating: –75 to 250 °C
Minimum bend radius: 6 mm (0.25 in) at least 6 mm (0.25 in) away
from sensor disk
Connector: Circular plastic M12 , male 8-pin connector
Main cable (M12 connector to pigtail)
Cable diameter: 0.622 cm (0.245 in)
Jacket material: Black semi-gloss polyvinyl chloride (PVC), UL VW-1
sunlight resistant for outdoor use
UL: AWM 10012 1000V 105 °C
7. Installation
If you are programming your data logger with Short Cut, skip Wiring (p. 9) and Data logger
programming (p. 11). Short Cut does this work for you. See QuickStart (p. 2) for a Short Cut
tutorial. This section discusses the following:
7.1 Circuit diagrams 8
7.2 Wiring 9
7.3 Data logger programming 11
7.4 Placement on a photovoltaic (PV) module 13
7.5 Mounting/cable strain relief 13
7.6 Cable resistance/long cable lengths 16
7.7 Electrical noisy environments 17
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7.1 Circuit diagrams
FIGURE 7-1 (p. 8) provides the circuit diagram for the 2-wire configuration. FIGURE 7-2 (p. 8)
provides the circuit diagram for the 4-wire configuration.
FIGURE 7-1. 2-Wire Circuit Diagram
FIGURE 7-2. 4-Wire Circuit Diagram
CS241 PT-1000 Class A, Back-of-Module Temperature Sensor8

7.2 Wiring
The CS241 sensor head includes a short, white cable with a circular plastic M12 type male 8-pin
connector. A second cable with a mating circular plastic M12 type female 8-pin connector is used
to attach the sensor to the data logger (see FIGURE 7-3 (p. 9)). This cable is typically a black UV
resistant, semi-gloss cable purchased with the CS241. However, a user-supplied cable can be
used. Table 7-1 (p. 10) and Table 7-2 (p. 11) show the pin configuration. Using connectors between
the sensor head and the data logger cable allows in-field sensor head replacement without
disconnecting the cable from the data logger. Detailed information about the cables are
provided in the Specifications (p. 6).
FIGURE 7-3. CS241 with black UV-resistant, semi-gloss cable
A fixed resistor is in the M12, male connector (see the following figure).
CS241 PT-1000 Class A, Back-of-Module Temperature Sensor9


FIGURE 7-4. Resistor in M12 male connector. Right image shows pin numbers.
The data logger can measure the CS241 using either a 2-wire or 4-wire configuration. The 2-wire
configuration accuracy decreases, relative to the 4-wire, as a function of the cable length. The
4-wire configuration eliminates resistance due to cable length and is the most accurate way to
measure this sensor. The following tables provide the data logger connections for the 2-wire and
4-wire configurations.
Table 7-1: Wire color, function, and data logger connection for 2-wire configuration
Wire color Pin
number Wire function Data logger connection
Red 1 Voltage excitation U configured for voltage excitation1, EX,
VX (voltage excitation)
Red 2 Voltage excitation U configured for voltage excitation1, EX,
VX (voltage excitation)
White 3 Signal U configured for single-ended analog input1,
SE (single-ended, analog-voltage input)
White 4 Signal U configured for single-ended analog input1,
SE (single-ended, analog-voltage input)
Black 5 Signal reference ⏚ (analog ground)
Black 6 Signal reference ⏚ (analog ground)
Clear N/C Shield ⏚ (analog ground)
1U terminals are automatically configured by the measurement instruction.

CS241 PT-1000 Class A, Back-of-Module Temperature Sensor10

Table 7-2: Wire color, function, and data logger connection for 4-wire configuration
Wire
color
Pin
number Wire function Data logger connection
Red 1 Voltage excitation U configured for voltage excitation1, EX,
VX (voltage excitation)
Red 2 Signal, high U configured for differential input1,
DIFF H (differential high, analog-voltage input)
White 3 Signal reference U configured for differential input1,
DIFF L (differential low, analog-voltage input)
White 4 Signal, high U configured for differential input1,
DIFF H (differential high, analog-voltage input)
Black 5 Signal reference U configured for differential input1,
DIFF L (differential low, analog-voltage input)
Black 6 Ground ⏚ (analog ground)
Clear N/C Shield ⏚ (analog ground)
1U terminals are automatically configured by the measurement instruction.
7.3 Data logger programming
Short Cut is the best source for up-to-date data logger programming code. If your data
acquisition requirements are simple, you can probably create and maintain a data logger
program exclusively with Short Cut. If your data acquisition needs are more complex, the files that
Short Cut creates are a great source for programming code to start a new program or add to an
existing custom program.
NOTE:
Short Cut cannot edit programs after they are imported and edited in CRBasic Editor.
A Short Cut tutorial is available in QuickStart (p. 2). If you wish to import Short Cut code into
CRBasic Editor to create or add to a customized program, follow the procedure in Importing
Short Cut code into CRBasic Editor (p. 19). Programming basics for CRBasic data loggers are
provided in the following section. Downloadable program example is available at
www.campbellsci.com/downloads/cs241-program-example .
If applicable, please read Electrical noisy environments (p. 17) and Cable resistance/long cable
lengths (p. 16) prior to programming your data logger.
CS241 PT-1000 Class A, Back-of-Module Temperature Sensor11

7.3.1 Resistance measurement and conversion to
temperature
The CS241 program needs to measure the resistance of the CS241 then convert that resistance
measurement to temperature. Accurate resistance measurements require a high-precision fixed
resistor with low thermal coefficient. The CS241 includes a 1000 Ohm metal film resistor with
0.01% accuracy and 2ppm thermal coefficient in the connector on the sensor side.
A 4-wire measurement using two differential analog terminals provides the most accurate
measurement and gets rid of resistance of the long cable lengths often needed in a field
installation. The following is a typical 4-wire measurement instruction for the CR1000X data
logger:

BrHalf4W(CS241X,1,mV200,mV200,1,VX1,1,500,True,True,0,15000,1,0)
'Convert ratio to ohms
CS241Rs=CS241X *1000 '(1000 is the value of the fixed resistor)
'Calculate temperature from resistance
'1000 is the resistance of the PRT at 0 degree C
PRTCalc(CS241T_4W,1,CS241Rs/1000,1,1,0)
A 2-wire measurement using only one single ended analog terminal can also measure the
sensing element resistance. In this case, the sensor-cable resistance (Rw) is included in the
measurement. With careful analysis of the circuit, some of this error can be removed if the cable
resistance is known. The cable resistance is provided on the sensor cable for this purpose. This
resistance will vary with temperature and hence the correction is only approximate. The following
is a typical 2-wire instruction for the CR1000X:

BrHalf(CS241X,1,mV200,5,VX1,1,500,True,0,15000,1,0)
'Convert ratio to ohms and remove cable resistance
'1000 is the value of the fixed resistor
CS241Rs=1000*((1-CS241X)/CS241X) + (Rw/2)*(1-2*CS241X)/CS241X)
'Calculate temperature from resistance
'1000 is the resistance of the PRT at 0 degree C
PRTCalc(CS241T_2W,1,CS241Rs/1000,1,1,0)
Where:
Rw is the cable resistance as shown on the cable
NOTE:
The CS241 is wired differently from what is shown in the help for instruction BrHalf().
CS241 PT-1000 Class A, Back-of-Module Temperature Sensor12

7.4 Placement on a photovoltaic (PV)
module
The PV module may or may not have distinctive photocells. If the PV module does not have
distinctive photocells, center the sensor on the back of the PV module. If the module has several
distinctive photocells, center the sensor on the back of the photocell that is the middle of the PV
module.
7.5 Mounting/cable strain relief
CAUTION:
Before mounting, the installers need to wash their hands and then clean the back of the PV
module or other device using the isopropyl alcohol pad shipped with the sensor.
7.5.1 Adhesive mounting strip
A pressure-activated adhesive mounting strip is adhered to the flat surface of the aluminum disk.
To mount the sensor, remove the paper from the mounting strip and place the disk on the back
of the PV module or other device. Press the disk firmly for 2 to 3 seconds to initiate long-term
bonding of the sensor to the surface. The mounting strip must be adhered to a clean surface for
its adhesive to function properly.
CAUTION:
Do not use epoxy to secure the sensor head to a PV module.
7.5.2 Cable strain relief
NOTE:
Placement of the cable inside a rugged conduit is advisable for cable runs over 4.5 m (15 ft),
especially in locations subject to digging, mowing, traffic, power tools, animals, or lightning
strikes.
The cable must be properly strain relieved after mounting the sensor to the measurement
surface. To accomplish this, the CS241 comes with three cable ties and three edge clips.
CS241 PT-1000 Class A, Back-of-Module Temperature Sensor13

1. Fasten the edge clips at the top of the PV module in the following locations:
a. Above the sensor
b. Next to the cable connector
CS241 PT-1000 Class A, Back-of-Module Temperature Sensor14

c. At a top corner of the PV module
2. Use the cable ties to secure the cable to the edge clips.
7.5.3 Extreme sealing tape
The CS241 was designed with principles to minimize surface area and mass. This design
minimizes the effects of installation on bifacial modules and also increases the adhesion
properties of the sensor to the module surface. When back-of-module temperatures may exceed
150°C, use extreme sealing tape for additional adhesion and cabling relief.
To ensure that the sensor disk and cable are adequately fastened to the measurement surface,
use three strips of tape in two places each:
1. For strain relief, place the first strip of tape across the cable 20 to 40cm (8 to 16in) from the
sensor head and rub the tape surface to remove bubbles.
2. Place the other strips of tape perpendicular and on top of the first strip of tape and rub the
tape surface to remove bubbles. These strips of tape should form an H (FIGURE 7-5 (p. 16)).
3. To secure the sensor to the module surface, remove the paper from the bottom of the disk
and adhere the disk to the PV module (Placement on a photovoltaic (PV) module (p. 13)).
4. Place a strip of tape across the sensor head, perpendicular to the cable and rub the tape
surface to remove bubbles. Rub as close as possible to the sensor disk.
5. Place the two other strips of tape on the ends of the sensor disk, perpendicular to the first
piece of tape and parallel to the cable then rub the tape surface into the module surface.
See the following figure.
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FIGURE 7-5. Proper tape usage
7.6 Cable resistance/long cable lengths
Placement of the cable inside a rugged conduit is advisable for cable runs over 4.5 m (15 ft),
especially in locations subject to digging, mowing, traffic, power tools, animals, or lightning
strikes.
Cable resistance can cause significant error (FIGURE 7-6 (p. 17)). The 4-wire half bridge
configuration is the best configuration for long cable lengths.
CS241 PT-1000 Class A, Back-of-Module Temperature Sensor16

FIGURE 7-6. BrHalf (2-wire half bridge) measurement error as a function of cable length
The heat shrink label on the cable provides the cable resistance (ohms). When using the 2-wire
configuration, subtract this cable resistance from the measured resistance value. The value
included on the label is calculated with the following equation:
Cable resistance = 0.0274 ohm/feet x cable length (in feet)
Additional settling time may be required for cable lengths longer than 91 m (300 ft), where
settling time is the delay before the measurement is made. The 60 and 50 Hz integration options
include a 3 ms settling time; longer settling times can be typed into the Settling Time
parameter in the BrHalf4W() or BrHalf() instruction.
7.7 Electrical noisy environments
AC power lines, pumps, power inverters, and motors can be the source of electrical noise. If the
sensor or data logger is located in an electrically noisy environment, the sensor should be
measured with the 60 or 50 Hz rejection option.
CS241 PT-1000 Class A, Back-of-Module Temperature Sensor17

8. Maintenance and
troubleshooting
NOTE:
For all factory repairs, customers must get an RMA number. Customers must also properly fill
out a “Declaration of Hazardous Material and Decontamination” form and comply with the
requirements specified in it. Refer to the Assistance page at the back of this manual for more
information.
8.1 Maintenance
The CS241 sensor requires minimal maintenance. Periodically check cabling for proper
connections, signs of damage, and possible moisture intrusion.
8.2 Troubleshooting
Symptom: Temperature is NAN, –INF, –9999, –273
Verify wiring of sensor to the data logger; cross-reference data logger program or the
measurement system wiring diagram.
Symptom: Incorrect Temperature
Check the cable for signs of damage and possible moisture intrusion.
Check measurement instruction multiplier and offset.
Symptom: Unstable Temperature
Make sure the clear shield wire is connected to data logger ground, and the data logger is
properly grounded. Try using the 60 or 50 Hz integration options and/or increasing the
settling time.
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