Consultation with substance

The structure of the sensor element of reference cells corresponds to that of a PV module; thus, the spectral sensitivity (spectral response, SR) and tilt error (incident angle modifier, IAM) of the reference cell are very comparable to the properties of PV modules. Pyranometers, on the other hand, behave very differently from PV modules due to their design with a glass dome and black receiver surface as the sensor element. 

These reference solar cells are therefore preferable as a reference for monitoring PV systems.

The measurement uncertainty of the calibration and the measurement uncertainty in operation with vertical light incidence and spectrum AM1.5 are equivalent for the reference cells of IMT and Class A pyranometers. The deviations of reference cells with oblique light incidence and deviating light spectrum correspond to the behaviour of PV modules and are therefore intentional properties of the IMT sensors and not measurement errors. 

The reference cells are therefore particularly suitable for PV monitoring.

Si sensors used for monitoring of PV installations must be installed with the same alignment and inclination as the PV generator. The mounting location should be free of shading as far as possible.
To facilitate maintenance and cleaning of the Si-Sensor, the Si-Sensor should be mounted in an easily accessible place.

The measurement uncertainty of the calibration of IMT Technology's reference cells is 1.2%, making it the world leader in reference cells for PV monitoring.
For Class A reference cells in accordance with IEC 61724-1:2021, a calibration measurement uncertainty of at least 2.0 % is required.
Thanks to the extremely high reproducibility of IMT Technology's calibration, different system locations can be excellently compared. And even after replacing sensors, you will continue to receive consistent measurement data on solar irradiance.

1. When determining the performance ratio (PR), the measurement error of the reference cell is directly included in the error of the PR determination. Since 0.1% can be decisive in the context of PR guarantees, it is extremely important to use very accurate reference cells for irradiance measurement. This is the only way to secure investments that are acceptable to banks.
2. Very low measurement uncertainty of the reference cells and very good reproducibility of the calibration enable precise monitoring of your PV system. This allows errors to be detected at an early stage and unnecessary service calls to be avoided.

In principle, we offer suitable sensors for almost every data logger or monitoring system used in photovoltaics. The type of input from the data logger or inverter is decisive for the selection of the suitable sensor type. We offer silicon solar radiation sensors and temperature sensors with various analogue outputs (e.g. 10 V or 20 mA) and digital versions with RS485 / MODBUS. IMT Technology products are compatible with almost all systems that require sensors with RS485 / MODBUS. In our download area you will find instructions for configuring the most common monitoring systems in conjunction with sensors with RS485 / MODBUS.

All Si sensors with RS485/MODBUS from IMT Technology measure solar irradiance and cell temperature. Some sensor types can also measure PV module temperature, ambient temperature and wind speed. In our download area you will find an overview of our sensor solutions with RS485/MODBUS.

Even if the cell temperature measurement is very precise, it can only be used as a rough approximation for the PV module temperature. The reason for this is the different geometry of the sensor compared to a PV module.
If you require a direct PV module temperature measurement, we offer special module temperature sensors, either as separate sensors or according to the selection list of Si sensors, with directly connected temperature sensors (module temp. / ambient temp.).

The measurement of irradiance on the rear side is largely determined by the position of the sensor and is difficult because the radiation varies greatly due to different reflection and shading.
One option in accordance with IEC 61724-1:2021 is to mount the Si sensor directly on the PV substructure. This ensures that the sensor has the same orientation as the PV modules.
The Si sensors from IMT Technology are very well suited for measuring irradiance on the rear side. 

Due to their high measurement accuracy and linearity, no extra calibration is necessary.

For surge protection, it depends on how the other lightning and surge protection is realised at the installation site. If external lightning protection is installed and the sensors are installed inside the lightning protection, then surge protection is required for the transition between lightning protection zones 0B to 1. Without external lightning protection, this would be necessary for the transition between lightning protection zones 0A to 1. Surge protection is therefore usually required directly at the entry point into the building.