Campbell SR05 User manual

Revision:04/2020
Copyright © 2019 – 2020
Campbell Scientific, Inc.

Table of contents
1. Introduction 1
2. Specifications 1
3. Siting 2
4. Mounting procedure 2
5. Wiring 4
6. Register map 5
7. RS-485 programming 6
8. Analog programming 7
9. Example programs 8
10. Maintenance and troubleshooting 12
Table of Contents - i

1. Introduction
The SR05, manufactured by Hukseflux Thermal Sensors, is an ISO 9060:2018 spectrally flat Class C
(second class) pyranometer designed for general solar radiation measurements in agricultural
and meteorological networks and PV monitoring. Both analog output and Modbus over RS-485
are supported.
2. Specifications
ISO 9060:2018 classification: Spectrally flat Class C (second class)
Digital output: Modbus over 2-wire RS-485
Voltage output: 0 to 1 V
Analog output range: 0 to 1600 W/m²
Default Modbus address: 53
Response time (95 %): 18 s
Calibration uncertainty: < 1.8 % (k = 2)
Zero offset A: < 15 W/m² (unventilated) response to 200 W/m² net thermal
radiation
Zero offset B: < ± 4 W/m² response to 5 K/h change in ambient temperature
Spectral range: 285 to 3000 nm
Operatingtemperaturerange: –40 to 80 °C
Temperature response: < ± 0.4 % (–30 to 50 °C)
Operating voltage range: 5 to 30 VDC
Power consumption: <75 mW at 12 VDC
Weight: 0.35 kg (12.34 oz)
SR05 ISO Spectrally Flat Class C (Second Class) Pyranometer with Various Outputs 1

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.
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.
SR05 ISO Spectrally Flat Class C (Second Class) Pyranometer with Various Outputs 2

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.
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.
SR05 ISO Spectrally Flat Class C (Second Class) Pyranometer with Various Outputs 3

6. Verify mounting hardware is firmly tightened, and that the mounting bracket is at the
desired angle.
5. Wiring
Table 5-1 (p. 4) provides RS-485 wiring and Table 5-2 (p. 5) provides analog wiring.
Table 5-1: RS-485 wire color, function, and data logger connection
Wire color1Function Data logger
connection2
MeteoPV
connection Pin out
Green RS485 A- C(odd) A- 5
White RS485 B+ C(even) B+ 2
Red Power in (12 V) 12V 12V 1
Black Power ground G G 4
Clear Shield ⏚(analog ground) ⏚(analog ground)
1Blue wire is not used.
2Assumes the sensor directly connects to the data logger.
SR05 ISO Spectrally Flat Class C (Second Class) Pyranometer with Various Outputs 4

Table 5-2: Analog wire color, function and data logger connection
Wire color1Function Data logger connection Pin out
Blue Pyranometer signal high
Uconfigured for differential input2,
DIFF H (differential high, analog-voltage
input)
3
Pyranometer signal
reference
Uconfigured for differential input2, 3,
DIFF L (differential low, analog-voltage
input)3
Red Power in (12 V) 12V 1
Black Ground ⏚(analog ground) 4
Clear Shield ⏚(analog ground)
1Green and white wires are not used.
2Uterminals are automatically configured by the measurement instruction.
3Jumper to ⏚with user-supplied wire.
6. Register map
Table 6-1 (p. 5) provides the register map for the most commonly used values. A comprehensive
register map is available in the Hukseflux manual.
Table 6-1: RS-485 register map
Starting register
number
Register
count Data format Units Description
1 1 Signed 16 bit integer Modbus address
3 2 Signed 32 bit integer mW/m² Irradiance (temperature
compensated signal)
7 1 Signed 16 bit integer 0.01 °C Sensor body temperature
8 1 Signed 16 bit integer x 0.1 Ω Sensor electrical
resistance
9 1 Signed 16 bit integer Scaling factor irradiance
10 1 Signed 16 bit integer Scaling factor
temperature
SR05 ISO Spectrally Flat Class C (Second Class) Pyranometer with Various Outputs 5

Table 6-1: RS-485 register map
Starting register
number
Register
count Data format Units Description
11 2 Signed 32 bit integer nV Sensor voltage output
41 1 Signed 16 bit integer Serial number
42 2 Float µV/W/m2Sensor sensitivity
47 2 Signed 32 bit integer Calibration date
7. RS-485 programming
The RS-485 output can be directly read by a MeteoPV, CR6-series, CR1000X-series, or Modbus
RTU RS-485 network. Other Campbell Scientific data loggers can use an MD485 multidrop
interface to read the RS-485 output (refer to the MD485 manual).
A CR6 or CR1000X data logger programmed as a Modbus Master can retrieve the values stored in
the Input Registers. 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 sensor Modbus address. To collect all of the values, the
Start parameter needs to be 1 and the Length parameter needs to correspond with the
register count (see Register map (p. 5) ). ModbusOption is an optional parameter described in
the CRBasic Editor Help. Refer to Example programs (p. 8) for more information.
SR05 ISO Spectrally Flat Class C (Second Class) Pyranometer with Various Outputs 6

8. Analog programming
The pyranometer outputs a low level voltage that is measured using either the VoltDiff()
CRBasic instruction or VoltSE() CRBasic instruction.
CAUTION:
Nearby AC power lines, electric pumps, or motors can be a source of electrical noise. If the
sensor or data logger is located in an electrically noisy environment, the measurement should
be made with the 60 or 50 Hz rejection integration option as shown in the example programs.
If measurement time is not critical, the autorange option can be used in the VoltDiff() or
VoltSE() instruction; the autorange adds a few milliseconds to the measurement time.
Otherwise, select the input range as follows:
1. Estimate the maximum expected input voltage by multiplying the maximum expected
irradiance (in W × m–2) by the calibration factor (in μV / W × m–2). Divide the answer by
1000 to give the maximum in millivolt units.
2. Select the smallest input range that is greater than the maximum expected input voltage.
If electromagnetic radiation can be a problem, use an fN1 of 50 or 60 Hz. Select 60 Hz Noise
Rejection for North America and areas using 60 Hz AC voltage. Select 50 Hz Noise Rejection for
most of the Eastern Hemisphere and areas that operate at 50 Hz. The multiplier converts the
millivolt reading to engineering units. Table 8-1 (p. 7) provides the calculations required for the
various units. The offset will normally be fixed at zero (see Example programs (p. 8)).
Table 8-1: Multipliers required for flux density and total fluxes
Units Multiplier Output processing
W × m–2 M Average
MJ × m–2 M × t × 0.000001 Totalize
kJ × m–2 M × t × 0.001 Totalize
cal × cm–2 M × t × 0.0239 × 0.001 Totalize
cal × cm–2 × min–1 M × 1.434 × 0.001 Average
W × hr × m–2 M × t / 3600 Totalize
M = 1000/c, where c is the sensor output in μV / W × m–2
t = data logger program execution interval in seconds
SR05 ISO Spectrally Flat Class C (Second Class) Pyranometer with Various Outputs 7

9. Example programs
Table 9-1 (p. 8) provides wiring for the example programs. CRBasic Example 1 (p. 8) uses Modbus
over RS-485 and CRBasic Example 2 (p. 11) uses analog voltage measurements.
Table 9-1: Connections for example programs
Wire color Function RS-485 program
CR1000X connections
Analog program
CR1000X connection
Green RS485A C5 N/C
White RS485B C6 N/C
Red Power in (12 V) 12V 12V
Black Power ground G G
Blue Pyranometer signal high N/C 1H
Pyranometer signal
reference N/C Jumper 1L to ⏚with user- supplied wire
Clear Shield ⏚(analog ground) ⏚(analog ground)
CRBasic Example 1: CR1000X program using Modbus over RS-485 to measure the SR05
'CR1000X Series Datalogger
'Hukseflux SR2005 Pyranometer
'SR05 is an ISO 9060 Second Class pyranometer
'
Public CheckSensorID As Boolean
Dim SR05(15) As Long
Public SR05_IRR_TC 'Temperature compensated x 0.01 W/M^2
Public SR05_IRR 'Uncompensated x 0.01 W/M^2
Public SR05_BodyTemp As Float
Public SR05_SerialNumber As Float
Public SR05_CalDate As Long
Public SR05_Humidity As Float
Public SR05_ScaleFactor_IRR As Long
Public SR05_ScaleFactor_BodyTemp As Long
Public SR05_ElecResistance As Long
Public SR05_VoltageOut As Float
SR05 ISO Spectrally Flat Class C (Second Class) Pyranometer with Various Outputs 8