Campbell CS240 User manual

Revision: 08/2020
Copyright © 2017 – 2020
Campbell Scientific, Inc.

Table of contents
1. Introduction 1
2. Precautions 1
3. Initial inspection 2
4. QuickStart 2
5. Overview 5
6. Specifications 6
7. Installation 8
7.1 Placement on a photovoltaic (PV) module 8
7.2 Mounting/cable strain relief 8
7.2.1 Adhesive mounting strip 9
7.2.2 Extreme sealing tape 9
7.2.3 Strain relief of CS240DM analog-to-digital module 11
7.3 Wiring 11
7.3.1 CS240-to-data-logger wiring 12
7.3.2 CS240DM wiring 13
7.4 Data logger programming 14
7.4.1 CS240 programming 14
7.4.1.1 Resistance measurement 14
7.4.1.2 Converting resistance measurement to temperature 15
7.4.2 CS240DM programming 15
8. Operation 16
8.1 Electrical noisy environments 16
8.2 Long cable lengths 16
8.2.1 CS240 cable resistance/long cable lengths 16
8.2.2 CS240DM long cable lengths 17
8.3 Modbus register map 18
8.4 CS240DM and Device Configuration Utility 19
9. Maintenance and troubleshooting 21
9.1 Maintenance 21
Table of Contents - i

9.2 Troubleshooting 21
Appendix A. Importing Short Cut code into CRBasic Editor 22
Appendix B. Example programs 23
B.1 CS240 two-wire configuration programs 24
B.2 CS240 four-wire configuration programs 28
B.3 CS240DM program 31
Appendix C. Sensor material properties 33
C.1 3M F9473PC adhesive 33
Table of Contents - ii

1. Introduction
The CS240 and CS240DM temperature sensors use a precision 1000 ohm class A platinum
resistance thermometer (PRT) to measure temperature. They are designed for measuring the
back-of-photovoltaic (PV) module temperature but also can be used to measure the surface
temperature of other devices. The CS240 can be measured with a 2-wire or 4-wire configuration
and is compatible with most Campbell Scientific data loggers. The CS240DM has a digital RS-485
output that can be directly read by a MeteoPV, CR6, CR1000X, or Modbus RTU RS-485 network.
Other Campbell Scientific data loggers can use an MD485 multidrop interface to read the
CS240DM output.
NOTE:
This manual provides information only for CRBasic data loggers. The CS240 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 with ethyl alcohol.
lDo not place tape over the sensor molding; only place tape on the metal disk portion of
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. 8)).
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.
CS240 and CS240DM PT-1000 Class A, Back-of-Module Temperature Sensors 1

3. Initial inspection
lUpon receipt of the sensor, inspect the packaging and contents for damage. File damage
claims with the shipping company.
lThe model number, cable length, and cable resistance (CS240 only) 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
The information provided in this section is for the CS240.
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, PC400, or PC200W.
The following procedure also shows using Short Cut to program the CS240 and CS240DM.
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 CS240. 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 CS240 and CS240DM, and is printed on the heat shrink label
attached to the sensor cable.
CS240 and CS240DM PT-1000 Class A, Back-of-Module Temperature Sensors 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.
CS240 and CS240DM PT-1000 Class A, Back-of-Module Temperature Sensors 3

6. In Output Setup, type the scan rate, a meaningful table name, and the Data Output
Storage Interval.
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, PC400, or PC200W to make
sure it is making reasonable measurements.
CS240 and CS240DM PT-1000 Class A, Back-of-Module Temperature Sensors 4

5. Overview
The CS240 and CS240DM are surface mountable platinum resistive thermometers (PRT) that
measure back-of-module temperature for solar energy applications. They use a precision PT-1000
class A PRT to provide the highest level of accuracy. To withstand the harsh treatment commonly
seen in 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. If the
temperature may exceed 70 °C, extreme sealing tape is also required to secure the sensor.
The CS240DM includes a Campbell Scientific precision analog-to-digital, smart-sensor module
for making the measurements. The module design is optimized for the class A PRT that
minimizes self-heating and lead-wire resistance. Measurement electronics are surge protected
with 1200 V isolation and environmentally protected with a rugged overmolding with an IP65
rating.
The CS240 and CS240DM provide 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.
FIGURE 5-1. CS240/CS240DM temperature sensor
CS240 and CS240DM PT-1000 Class A, Back-of-Module Temperature Sensors 5

Features:
lPrecision PT-1000 class A sensing element
lUser-selectable and standard cable lengths offered
lRugged design holds up in harsh conditions and conduit installations
lSelf-adhesive backing for easy mounting lasts decades
lCS240 has 2-wire or 4-wire configurations to satisfy accuracy even at long cable lengths
lCS240 compatible with Campbell Scientific CRBasic data loggers: CR6, CR3000, CR1000X,
CR800 series, CR300 series, CR1000, and CR5000
lCS240DM compatible with Campbell Scientific CRBasic data loggers: CR6, CR1000X,
CR3000 (with MD485), CR800 series (with MD485), CR300 series (with MD485), CR1000
(with MD485),
lCS240DM easily interfaces with the MeteoPV Platform without coding
lCS240DM can connect directly with Modbus RTU RS-485 Networks
lCalibration services with certification available
6. Specifications
Sensor: Precision 1000 ohm class A platinum sensing element
Class A sensor accuracy: ± (0.15 + 0.002t) °C
Temperature range: –40 to 135 °C
Temperature coefficient: TCR = 3850 ppm/K
Long-term stability: Max Ro drift = 0.04% after 1000 hours at 400 °C
CS240 measuring current: 0.1 to 0.3 mA
Disk diameter: 2.54 cm (1.0 in)
Overall sensor length: 6.35 cm (2.5 in)
Overmolded joint dimensions
Width: 1.12 cm (0.44 in)
Height: 1.47 cm (0.58 in)
Length: 5.72 cm (2.25 in)
Cable diameter: 0.622 cm (0.245 in)
Cable temperature rating: 105°C
Disk material: Anodized aluminum
CS240 and CS240DM PT-1000 Class A, Back-of-Module Temperature Sensors 6

Weight: 90.7 g (0.2 lb) with 3.2 m (10.5 ft) cable
CS240DManalog-to-digitalmodule: 24-bit ADC
A/D measurement uncertainty: ±0.015 °C
Supply voltage: 5 to 30 VDC
Power consumption: 15 mA
Surge protection: 1200 V isolation
Environmental protection: Rugged overmolding with IP65 rating
Approvals: UL AWM 2586 1000V 105 °C; CSA AWM 600V 105 °C FT1
Conforms with Electromagnetic Compatibility Directive
(EMC)
Conforms with the Restriction of Hazardous Substances
Directive (RoHS2)
Compliance: View compliance documents at:
www.campbellsci.com/cs240 or
www.campbellsci.com/cs240dm
Compliant with IEC 60751, DIN EN 60751,
Industrial Design (IEC Class 4) (according to IEC 751)
CS240 cable
Jacket material: Black semi-gloss PVC, UL VW-1 sunlight resistant for
outdoor use
Wire size and type: 24 AWG (7/32) tinned copper
Nominal wire diameter: 0.61 mm (0.024 in)
Insulation type: PVC
UL: AWM 10012 1000V 105 °C
Filler: Fibrillated polypropylene as required for uniform
round construction.
Drain: 24 AWG (7/32) tinned copper (cabled, touching foil)
Shield: Aluminum/mylar (100% coverage, 25% minimum overlap,
foil facing in)
CS240 and CS240DM PT-1000 Class A, Back-of-Module Temperature Sensors 7

CS240DM cable
Features: High flex construction with jacket for pulling through
conduit
Jacket material: Black semi-gloss PVC, UL VW-1 sunlight resistant for
outdoor use; weld spatter and oil resistant
Nominal wire diameter: 0.61 mm (0.024 in)
Agency approvals: UL AWM Style 2463 and NEC/CEC CMX outdoor
7. Installation
If you are programming your data logger with Short Cut, skip Wiring (p. 11) and Data logger
programming (p. 14). Short Cut does this work for you. See QuickStart (p. 2) for a Short Cut
tutorial. This section discusses the following:
7.1 Placement on a photovoltaic (PV) module 8
7.2 Mounting/cable strain relief 8
7.3 Wiring 11
7.4 Data logger programming 14
7.1 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.
7.2 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 with ethyl alcohol.
CS240 and CS240DM PT-1000 Class A, Back-of-Module Temperature Sensors 8

7.2.1 Adhesive mounting strip
An 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 adhere it to the back of the PV module or
other device. 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.
7.2.2 Extreme sealing tape
Use extreme sealing tape for cable strain relief. A yellow label on the cable indicates where the
cable must be secured (FIGURE 7-1 (p. 10)). If the temperature might exceed 70°C, extreme
sealing tape is required to better secure the sensor to the measurement surface.
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 just below the yellow heat
shrink (FIGURE 7-2 (p. 10)) 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 7-2 (p.
10)).
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. 8)).
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.
CAUTION:
Do not place tape over the sensor molding; only place tape on the metal disk portion
of the sensor.
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 FIGURE 7-2 (p. 10).
CS240 and CS240DM PT-1000 Class A, Back-of-Module Temperature Sensors 9

FIGURE 7-1. Strain relief label on the cable
FIGURE 7-2. Proper tape usage
CS240 and CS240DM PT-1000 Class A, Back-of-Module Temperature Sensors 10

7.2.3 Strain relief of CS240DM analog-to-digital module
The CS240DM has an analog-to-digital, smart-sensor module incorporated that needs to be
secured to the side of PV module. Use two cable tie tabs and cable ties to do this.
7.3 Wiring
FIGURE 7-3 (p. 11) provides the circuit diagrams for the CS240 2-wire configuration. FIGURE 7-4
(p. 12) provides the circuit diagram for the CS240DM or the CS240 4-wire configuration.
FIGURE 7-3. 2-Wire Circuit Diagram
CS240 and CS240DM PT-1000 Class A, Back-of-Module Temperature Sensors 11

FIGURE 7-4. 4-Wire Circuit Diagram
7.3.1 CS240-to-data-logger wiring
The data loggers can measure the CS240 by using a 2-wire or 4-wire configuration (Table 7-1 (p.
12) and Table 7-2 (p. 13)). 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 CS240 is shipped ready for the 2-wire
configuration. The wires used only for the 4-wire configuration are taped to the side of the cable.
Table 7-1: Wire color, function, and data logger connection for the CS240 2-wire configuration
Wire color Wire function Data logger connection terminals
Black Voltage excitation
input
Uconfigured for voltage excitation1,
EX,VX (voltage excitation)
White Analog voltage output Uconfigured for single-ended analog input1,
SE (single-ended, analog input)
Red Reference ⏚(analog ground)
1Uterminals are automatically configured by the measurement instruction.
CS240 and CS240DM PT-1000 Class A, Back-of-Module Temperature Sensors 12

Table 7-2: Wire color and data logger connection for the CS240 4-wire configuration
Wire color Wire function Data logger connection terminals
White Analog voltage output1Uconfigured for differential high analog input2,
DIFF H (differential high, analog-voltage input)
Black Reference1Uconfigured for differential low analog input2,
DIFF L (differential low, analog-voltage input)
Red Voltage excitation input Uconfigured for voltage excitation2,
EX,VX (voltage excitation)
Red Analog voltage output3Uconfiguredfordifferentialhighanaloginput2,
DIFF H (differential high, analog-voltage input)
White Reference3Uconfigured for differential low analog input2,
DIFF L (differential low, analog-voltage input)
Black Ground ⏚(analog ground)
Clear/shield Shield ⏚(analog ground)
1First differential terminal in the BrHalf4W() instruction.
2Uterminals are automatically configured by the measurement instruction.
3Second differential terminal in the BrHalf4W() instruction.
7.3.2 CS240DM wiring
The CS240DM can have a standard cable or a 3-twisted pair cable (Table 7-3 (p. 13)). The wiring
for the CS240DM is also available in the Device Configuration Utility and the MeteoPV User
Interface.
Table 7-3: Wire Color, Station Connection, and Function for the CS240DM
Standard cable
wire color
3-twisted pair cable
wire color
Station (data logger)
terminal Function
Blue Green A– (Codd) RS-485 A/A' [–]
White/blue striped White B+ (Ceven) RS-485 B/B' [+]
Brown Red 12V 5 to 30 VDC
White/brown striped Black GGround (power)
Green Yellow G(⏚) Modbus common
-- Clear G(⏚) Shield
CS240 and CS240DM PT-1000 Class A, Back-of-Module Temperature Sensors 13

7.4 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. 22). Programming basics for CRBasic data loggers are
provided in the following section. Complete program examples for select CRBasic data loggers
can be found in Example programs (p. 23)..
If applicable, please read Electrical noisy environments (p. 16) and Long cable lengths (p. 16) prior
to programming your data logger.
7.4.1 CS240 programming
The CS240 program needs to measure the resistance of the CS240 then convert that resistance
measurement to temperature.
7.4.1.1 Resistance measurement
CRBasic instructions used to measure resistance are the BrHalf4W (4-wire configuration) or
BrHalf (2-wire configuration). The BrHalf4W() instruction reduces cable errors, and the
BrHalf() instruction uses the fewest input terminals.
A typical BrHalf4W() instruction is:
BrHalf4W(CS240X,1,mV200,mV200,U1,U5,1,350,True,True,0,60,1,0)
A typical BrHalf() instruction is:
BrHalf(CS240X,1,mV200,U7,U3,1,350,True,0,60,1,0)
Use a multiplier of 1.0 and offset of 0.0 in the instructions.
CS240 and CS240DM PT-1000 Class A, Back-of-Module Temperature Sensors 14

7.4.1.2 Converting resistance measurement to temperature
The PRTCalc() instruction converts the ratio Rs/Ro to temperature, where Rs is the measured
resistance of the RTD, and Ro is the resistance of the RTD at 0 degrees Celsius (1000 Ω).
A typical PRTCalc() instruction is:
PRTCalc(PRTtemp,1,Rs/1000,1,1,0)
If the BrHalf instruction (2-wire configuration) was used to measure resistance, the following
expression also must precede the PRTCalc instruction:
Rs=CS240X*(1000+Rc)/(1–CS240X)–Rc
Where CS240X value returned by the BrHalf instruction and Rcis the cable resistance provided
on the cable label.
7.4.2 CS240DM programming
NOTE:
Programming basics for the CR6 and CR1000X data loggers are provided in this section.
Contact Campbell Scientific if using a data logger that requires an MD485 interface.
A CR6 or CR1000X data logger programmed as a Modbus Master can retrieve the values stored in
the CS240DM Input Registers (Modbus register map (p. 18)). To do this, the CRBasic program
requires a SerialOpen() instruction followed by the ModbusMaster() instruction.
The SerialOpen instruction has the following syntax:
SerialOpen (ComPort, Baud, Format, TXDelay, BufferSize, Mode )
The Format is typically set to logic 1 low;even parity,one stop bit,8 data bits. The Mode
parameter should configure the ComPort as RS-485 half-duplex, transparent.
The ModbusMaster() instruction has the following syntax:
ModbusMaster (Result,ComPort,Baud,Addr,Function, Variable, Start, Length, Tries,
TimeOut, [ModbusOption] )
The Addr parameter must match the CS240DM Modbus address. Each Modbus address must be
unique on a Modbus network. The default value for the Modbus address is the last two digits of
the sensor serial number, with exceptions for serial numbers ending in 00 and 01. These
exceptions default to Modbus addresses of 110 and 111, respectively. To collect all of the
CS240 and CS240DM PT-1000 Class A, Back-of-Module Temperature Sensors 15

CS240DM values, the Start parameter needs to be 1and the Length parameter needs to be 5.
ModbusOption is an optional parameter described in the CRBasic Editor Help.
For more information, refer to CS240DM program (p. 31).
8. Operation
This section discusses the following:
8.1 Electrical noisy environments 16
8.2 Long cable lengths 16
8.3 Modbus register map 18
8.4 CS240DM and Device Configuration Utility 19
8.1 Electrical noisy environments
AC power lines, pumps, power inverters, and motors can be the source of electrical noise. If the
CS240 sensor or data logger is located in an electrically noisy environment, the CS240 sensor
should be measured with the 60 or 50 Hz rejection option.
8.2 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.
8.2.1 CS240 cable resistance/long cable lengths
Cable resistance can cause significant error (FIGURE 8-1 (p. 17)). The 4-wire half bridge
configuration is the best configuration for long cable lengths.
CS240 and CS240DM PT-1000 Class A, Back-of-Module Temperature Sensors 16

FIGURE 8-1. BrHalf (2-wire half bridge) measurement error as a function of cable length
The heat shrink label on the CS240 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.
8.2.2 CS240DM long cable lengths
Digital data transfer eliminates offset errors due to cable lengths. However, digital
communications can break down when cables are too long, resulting in either no response from
the sensor or corrupted readings. Maximum cable lengths depend on the number of sensors
connected, the type of cable used, and the environment of the application. Follow these
guidelines when using long cables:
CS240 and CS240DM PT-1000 Class A, Back-of-Module Temperature Sensors 17