Campbell SMP10 User manual

Revision: 01/2021

Campbell Scientific, Inc.

Table of contents

1. Introduction 1

2. Specifications 1

3. Siting 2

4. Mounting procedure 2

5. Wiring 3

6. Modbus register map 4

7. Modbus programming 5

8. Analog programming 6

9. Maintenance and troubleshooting 7

Table of Contents - i

1. Introduction

The SMP10 pyranometer, manufactured by Kipp & Zonen and cabled by Campbell Scientific,

measures solar radiation with a high-quality blackened thermopile protected by two glass domes.

Its flat spectral sensitivity makes it ideal for applications in natural sunlight, under plant canopies,

and in greenhouses or buildings. Communications to on-site RTUs, SCADA systems, or other data

acquisition systems are simplified with the industry-standard Modbus RTU communications

protocol. Typical uses include environmental monitoring, solar resource assessment, and solar

power performance applications.

Typically, this pyranometer is oriented perpendicular to the Earth’s surface to measure global

horizontal irradiance (GH). Diffuse sky radiation can also be measured with the use of a shade

mechanism.

2. Specifications

ISO 9060:2018 classification: class A (secondary standard)

Output: Modbus over 2-wire RS-485 or 0 to 1 V

Analog output range: 0 to 1600 W/m²

Modbus output range: –400 to 4000 W/m²

Zero offset A: < 7 W/m²

Zero offset B: < 2 W/m²

Spectral range: 285 to 2800 nm

Operating temperature range: –40 to 80 °C

Temperature response: < 1% (–20 to 50 °C); < 2% (–40 to 70 °C)

Operating voltage range: 5 to 30 VDC

Power consumption: <55 mW at 12 VDC

Weight without cable: 0.6 kg (1.3 lb)

SMP10 Pyranometer 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

lCM256 mounting bracket

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.

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. Use the two set screws to secure the bracket to the crossarm or pole as shown in the

following figure. 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.

SMP10 Pyranometer 2

5. Verify mounting hardware is firmly tightened, and that the mounting bracket is at the

desired angle.

5. Wiring

Table 5-1 (p. 3) provides RS-485 wiring and Table 5-2 (p. 4) provides analog wiring.

Table 5-1: RS-485 pin-out, wire color, function, and data logger connection

Wire color Pin-out Function Data logger

connection1MeteoPV connection

Grey 5 RS485A+ C(odd) A-

Yellow 4 RS485B- C(even) B+

White 7 Power in (12 V) 12V 12V

Black 8 Power ground G G

Blue 2 Ground ⏚(analog ground) ⏚(analog ground)

1Assumes the sensor directly connects to the data logger.

SMP10 Pyranometer 3

Table 5-2: Analog pin-out, wire color, function, and data logger connection

Wire color Pin-out Function Differential data logger

connection

Single-ended data logger

connection

Green 3 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)

Brown 6

Pyranometer

Signal

Reference

Uconfigured for

differential input1,DIFF L

(differential low, analog-

voltage input)

⏚(analog ground)

Blue 2 Ground ⏚(analog ground) ⏚(analog ground)

1U channels are automatically configured by the measurement instruction.

6. Modbus register map

Table 6-1 (p. 4) provides the register map for the most commonly used values. A comprehensive

Table 6-1: Modbus register map

Starting

number

count Data format Label Units Description

4 1 unsigned integer Status Device Status flags

5 1 signed integer Range

Range and scale factor sensor

data (determines number of

decimal places)

6 1 signed integer Sensor1 W/m2Temperature compensated net

radiation

7 1 signed integer RawData1 W/m2Net radiation

8 1 signed integer StDev1 W/m2

Standard deviation of

temperature compensated

radiation

SMP10 Pyranometer 4

Table 6-1: Modbus register map

Starting

number

count Data format Label Units Description

9 1 signed integer BodyTemp 0.1 °C Body temperature

10 1 signed integer VSupply VDC External power voltage

7. Modbus programming

The RS-485 output can be directly read by a MeteoPV, CR6-series, CR1000X, 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

described in the CRBasic Editor Help. A downloadable Modbus program is available at:

www.campbellsci.com/downloads/smp10-example-programs.

SMP10 Pyranometer 5

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 analog voltage

program available at: www.campbellsci.com/downloads/smp10-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 the downloadable analog voltage

program available at: www.campbellsci.com/downloads/smp10-example-programs).

SMP10 Pyranometer 6

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

9. Maintenance and

troubleshooting

The SMP10 has no service items requiring scheduled replacement. There is no accessible

desiccant cartridge to maintain. Use pure alcohol or distilled water and a lint-free cloth to clean

the dome, removing smears and deposits. Local conditions and application dictate cleaning

interval. Sophisticated research applications require daily cleaning. For typical PV applications,

clean once per week, bi-monthly, or monthly. The SMP10 should be recalibrated following

industry standard best practices such as ASTM G167, ISO 9846, ASTM E824 or ASTM G207 by an

accredited lab. The recommended recalibration interval is two years. Contact Campbell Scientific

for more information.

Unexpected results typically occur because of improper wiring or programming, electromagnetic

radiation, or damaged cables. Ensure that the data logger program includes the correct

parameters for the measurement instructions. Check for the presence of strong sources of

electromagnetic radiation. Check the cable for damage and ensure that it is properly connected

to the data logger.

SMP10 Pyranometer 7

Limited warranty

Products manufactured by Campbell Scientific are warranted by Campbell Scientific to be free

from defects in materials and workmanship under normal use and service for twelve months from

the date of shipment unless otherwise specified on the corresponding product webpage. See

Product Details on the Ordering Information pages at www.campbellsci.com. Other

manufacturer's products, that are resold by Campbell Scientific, are warranted only to the limits

extended by the original manufacturer.

Refer to www.campbellsci.com/terms#warranty for more information.

CAMPBELL SCIENTIFIC EXPRESSLY DISCLAIMS AND EXCLUDES ANY IMPLIED WARRANTIES OF

MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Campbell Scientific hereby

disclaims, to the fullest extent allowed by applicable law, any and all warranties and conditions

with respect to the Products, whether express, implied or statutory, other than those expressly

provided herein.

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