Silicon Solar Irradiance Sensors

Photovoltaic Reference Cells for PV Monitoring

i-EM is an official distributor of silicon sensor from Ingenieurbüro Mencke & Tegtmeyer GmbH since 2008. These photovoltaic reference cells offer an economical but robust and reliable solution for measuring solar irradiance levels, particularly for monitoring photovoltaic systems.

The design of these silicon solar irradiation sensors (Si sensors), which corresponds to that of a photovoltaic module, make these sensors ideally suited as a reference for monitoring photovoltaic systems. The spectral sensitivity of our sensors is very close to that of the PV modules with Silicon. In addition, for this type of modules, also the reflexion at the glass is nearly identical. So, the overall nearly identical behaviour of PV modules and our Si sensors for Spectral Response (SR) and Incident Angle Modifier (IAM) enables a precise analysis of photovoltaic yields using measured values from the sensors.

All the reference cells have consistent measuring ranges of the solar irradiance (0 to 1500 W/sqm) and the temperature (internal and for some models also external) of the sensor cell (-40 to +90°C), and a measurement uncertainty of the reference cells with temperature compensation is 5 W/sqm ± 2.5% of reading (see datasheet for more details).

The output of the sensors could be analogue (e.g. 0…10 V, 4…20 mA) or Modbus RS485. For the analogue models, the typical electrical connection is with 3 m shielded cable (but could be also provided at different lengths, up to 30m). Additionally to the irradiance measurement the silicon sensors with the extension “-T” are able to measure the temperature of the solar cell using a temperature sensor laminated to the back of the cell. This solar cell temperature can approximately be used as module temperature.

To minimize influences of temperature to the measuring signal all of the sensors with the extension “TC“ have an active temperature compensation. All sensors are calibrated in artificial sunlight against a reference cell calibrated at the Physikalisch-Technische Bundesanstalt (PTB, National Metrology Institute of Germany).

Technical Specifications

Typ Supply Temperature Compensation Irradiance Signal 0…1500 W/sqm Cell Temperature Signal -40…+90°C
Si-V-1.5TC 4…28 Vdc Yes 0…1.5 V
Si-V-1.5TC-T 5.5…28 Vdc Yes 0…1.5 V 0…2 V
Si-mV-85 None No 0…approx. 85 mV
Si-mV-85-Pt100 / -4L(1) None No 0…approx. 85 mV Pt100
Si-mV-85-Pt1000 / -4L(1) None No 0…approx. 85 mV Pt100
Si-I-420TC 12…28 Vdc Yes 4…20 mA
Si-I-420TC-T 12…28 Vdc Yes 4…20 mA 4…20 mA
Si-V-10TC 12…28 Vdc Yes 0…10 V
Si-V-10TC-T 12…28 Vdc Yes 0…10 V 0…10 V
Si-RS485TC-T 12…28 Vdc Yes RS485 RS485
Si-RS485TC-2T (2) 12…28 Vdc Yes RS485 RS485
Si-RS485TC-T-Tm (3) 12…28 Vdc Yes RS485 RS485
Si-RS485TC-2T-v (4) 12…28 Vdc Yes RS485 RS485

(1) “-4L“: Version with four wire connection of Pt100 / Pt1000

Notes about Digital Sensor:
(2) for Si-RS485TC-2T: Fixed connected ambient temperature sensor  Pt1000 with 3 m cable
(3) for Si-RS485TC-T-Tm: Fixed connected module temperature sensor Pt1000 with 3 m cable
(4) for Si-RS485TC-2T-v: Connector for one temperature sensor (Tamb-Si or Tmodul-Si) and one wind speed sensor (Vwind-Si)

Addendum -MB in type designation: Modbus protocol
Addendum -MT in type designation: M&T protocol

A selection table with notes with the correct digital Si sensor and optional external sensor you can find here.

Optional Sensor for Connection with Si-RS485TC-2T-v:
Module Temperature Sensor: Tmodul-Si (Pt1000)
Ambient Temperature Sensor: Tamb-Si (Pt1000)
Weather Protection for Ambient Temperature Sensor: Shield Tamb-Si
Windspeed Sensor: Vwind-Si