Campbell SR20-T2 User manual

Revision: 05/2020
Copyright © 2018– 2020
Campbell Scientific, Inc.

Table of contents
1. Introduction 1
2. QuickStart 1
3. Siting 4
4. Mounting procedure 5
5. Wiring 7
6. Analog programming 11
7. Integrated thermistor 12
8. Maintenance and troubleshooting 12
Appendix A. Importing Short Cut code into CRBasic Editor 14
Appendix B. SR20-T2 example programs 15
Table of Contents - i

1. Introduction
The SR20-T2, manufactured by Hukseflux Thermal Sensors, is an ISO 9060 spectrally flat Class A
(secondary standard) pyranometer that measures solar short-wave radiation in a full hemisphere
of the sky. It has a built-in case temperature sensor and embedded heater for removing dew and
light rain. It connects directly to a Campbell Scientific data logger and is designed for
applications that require high measurement accuracy in demanding applications such as
scientific meteorological observation networks and utility scale solar-energy-power production
sites.
2. QuickStart
A video that describes data logger programming using Short Cut is available at:
www.campbellsci.com/videos/cr1000x-datalogger-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, PC200W, PC400, or RTDAQ.
NOTE:
Short Cut uses the two-wire configuration to measure the integrated thermocouple.
The following procedure also shows using Short Cut to program the sensor.
1. Open Short Cut and click Create New Program.
2. Double-click the data logger model.
SR20-T2 ISO Spectrally Flat Class A (Secondary Standard) Pyranometer 1

3. In the Available Sensors and Devices box, type SR20 or locate the sensor in the Sensors >
Meteorological >Solar Radiation folder. Double-click the SR20-T2 ISO Secondary Standard
Pyranometer. Type the Sensitivity and temperature coefficient values listed on the
calibration sheet. These values are unique for each sensor.
SR20-T2 ISO Spectrally Flat Class A (Secondary Standard) Pyranometer 2

4. Click 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.
6. In Output Setup, type the scan rate, meaningful table names, and Data Output Storage
Interval.
SR20-T2 ISO Spectrally Flat Class A (Secondary Standard) Pyranometer 3

7. Select the measurement and its associated output option.
8. Click Finish and save the program. Send the program 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, PC400, RTDAQ, or PC200W to make
sure it is making reasonable measurements.
3. Siting
The solar radiation sensor is usually installed horizontally, but can also be installed at any angle
including an inverted position. Site the sensor to allow easy access for maintenance while ideally
avoiding any obstructions or reflections above the plane of the sensing element. It is important
to mount the sensor such that a shadow or a reflection will not be cast on it at any time. If this is
not possible, try to choose a site where any obstruction over the azimuth range between earliest
sunrise and latest sunset has an elevation not exceeding 5°. Diffuse solar radiation is less
influenced by obstructions near the horizon. The sensor should be mounted with the cable
pointing towards the nearest magnetic pole. For example, in the northern hemisphere, point the
cable toward the North Pole.
SR20-T2 ISO Spectrally Flat Class A (Secondary Standard) Pyranometer 4

4. Mounting procedure
Required tools:
lDiopter
lSolar compass
l8 mm (5/16-inch) open-end wrench for U-bolt nuts
1. On a level surface, level the solar radiation sensor using the leveling feet on the sensor.
Alternatively, remove the sensor leveling feet to allow it to be mounted directly to the
mounting bracket.
2. Secure the solar radiation sensor to the mounting bracket. The blue dots in the following
figure indicate the mounting holes used for this pyranometer.
3. Using a diopter in combination with a solar compass, install and orient the crossarm on the
tripod or the mast. If installing the mounting bracket on a vertical pole, ensure the pole is
truly vertical.
4. Secure the mounting bracket to the crossarm or vertical pole using the hardware included
with the mounting bracket. The CM255 uses one U-bolt, nuts, flat washers, and lock
washers to mount the bracket, as shown in the following figure.
SR20-T2 ISO Spectrally Flat Class A (Secondary Standard) Pyranometer 5

5. For pyranometers mounted horizontally, ensure the mounting bracket is horizontal in two
dimensions. For pyranometers mounted at an angle, set the mounting bracket angle to the
desired angle prior to tightening the mounting hardware.
SR20-T2 ISO Spectrally Flat Class A (Secondary Standard) Pyranometer 6

6. Verify mounting hardware is firmly tightened, and that the mounting bracket is at the
desired angle.
5. Wiring
Table 5-1 (p. 7) provides the 2-wire half bridge wiring and Table 5-2 (p. 8) provides the 4-wire
half bridge wiring. FIGURE 5-1 (p. 10) provides the schematic for the 2-wire configuration of the
integrated thermistor and FIGURE 5-2 (p. 10) provides the schematic for the 4-wire configuration
of the integrated thermistor.
Table 5-1: Pin-out, wire color, function, and data logger connection for 2-wire half bridge
Wire
color
Pin out Function Data logger connection
-PT -PW Differential Single-ended
White 7 7 Pyranometer
signal high
Uconfigured for
differential input1,DIFF H
(differential high, analog-
voltage input)
Uconfigured for single-
ended analog input1,SE
(single-ended, analog-
voltage input)
Green 5 9 Pyranometer
signal reference
Uconfigured for
differential input1,
DIFF L (differential low,
analog-voltage input)
⏚(analog ground)
Brown 4 4
Heater (polarity
does not matter,
1.5W at 12VDC)
Switched heater power:
SW,SW12,SW12V,
SW Battery (switched 12 V)
Constant heater power:
12V
Switched heater power:
SW,SW12,SW12V,
SW Battery (switched 12 V)
Constant heater power:
12V
Yellow 1 1 Heater ground G G
Red 2 2 Thermistor signal
Uconfigured for single-
ended analog input1,SE
(single-ended, analog-
voltage input)
Uconfigured for single-
ended analog input1,SE
(single-ended, analog-
voltage input)
Blue 6 6 Thermistor
reference ⏚(analog ground) ⏚(analog ground)
SR20-T2 ISO Spectrally Flat Class A (Secondary Standard) Pyranometer 7

Table 5-1: Pin-out, wire color, function, and data logger connection for 2-wire half bridge
Wire
color
Pin out Function Data logger connection
-PT -PW Differential Single-ended
Orange NC NC Thermistor
voltage excitation
Uconfigured for voltage
excitation1,EX,VX
(voltage excitation)
Uconfigured for voltage
excitation1,EX,VX
(voltage excitation)
Purple 3 3 Thermistor signal
Uconfigured for single-
ended analog input1,SE
(single-ended, analog-
voltage input)
Uconfigured for single-
ended analog input1,SE
(single-ended, analog-
voltage input)
Gray 8 8 Thermistor
reference ⏚(analog ground) ⏚(analog ground)
Black 9 5 Ground G G
Clear NC 9 Shield ⏚(analog ground) ⏚(analog ground)
1U channels are automatically configured by the measurement instruction.
Table 5-2: Pin-out, wire color, function, and data logger connection for 4-wire half bridge
Wire
color
Pin out Function Data logger connection
-PT -PW Differential Single-ended
White 7 7 Pyranometer
Signal High
Uconfigured for
differential input1,DIFF H
(differential high, analog-
voltage input)
Uconfigured for single-
ended analog input1,SE
(single-ended, analog-
voltage input)
Green 5 9 Pyranometer
Signal Reference
Uconfigured for
differential input1,DIFF L
(differential low, analog-
voltage input)
⏚(analog ground)
Brown 4 4
Heater (polarity
does not matter,
1.5 W at 12 VDC)
Switched heater power:
SW,SW12,SW12V,SW
Battery (switched 12 V)
Constant heater power:
12V
Switched heater power:
SW,SW12,SW12V,SW
Battery (switched 12 V)
Constant heater power:
12V
SR20-T2 ISO Spectrally Flat Class A (Secondary Standard) Pyranometer 8