TRITEC Support PV-measuring technology

Frequently asked questions

On our support website, we will answer all your questions on the subject of PV measuring technology. In our FAQ, we have compiled interesting facts and useful information about the application of the TRITEC characteristics measuring instrument TRI-KA. In addition, you may also ask us questions. The TRITEC product management is looking forward to your e-mail!

General questions on TRI-KA II

What can the TRI-KA measuring instrument measure?

On the DC side of the PV system, TRI-KA measures the open circuit voltage (UOC), the short circuit current (ISC) and the complete current-voltage characteristic.

How precise are TRI-KA measurements?

Meaningful measurements depend on several factors: Irradiation conditions must be constant. The sensor must have the same orientation & inclination as the string (module) to be measured. The module temperature must be measured at different points distributed in the string. Modules should not be excessively soiled. The TRI-KA device has a precision of +/- 5% of the calculated STC performance.

From which irradiation level can characteristic measurements be carried out for an STC evaluation of the modules?

According to the standard EN61829, characteristic measurements for an STC evaluation may only be carried out starting at a total irradiance of 700 W/m². For an electrical review (no STC evaluation! ) of the characteristic – e.g. curve of the characteristic, etc. –, irradiation starting at approx. 500 W/m² is already sufficient.

There are PV measuring devices working with 2 or 4 measuring leads. What’s the difference in this case?

The PV line as well as the measuring leads act as a resistance (depending on the line cross section) if current flows through the line. Part of the voltage drops in the lines. Measuring devices with 4 measuring leads circumvent this problem by taking two measuring leads to measure the voltage and the other two measuring leads to measure the current. This procedure only compensates for the voltage drop in the measuring leads, not the voltage drop of the two PV lines from inverter to string. TRI-KA works with 2 measuring leads. In the measuring device or in the PC software, a correction of the voltage drop can be activated so that it is mathematically compensated by the complete PV line.

The communication between TRI-KA and TRI-SEN is wireless. What happens if there is no radio connection or if it is interrupted?

TRI-SEN permanently measures the irradiation and sends it together with the measured module temperature and the angle of inclination from the sensor by radio to TRI-KA. Additionally, the measured data are temporarily stored in internal storage in the event that the radio connection cannot be established. The missing sensor data from TRI-KA measurements can then be subsequently synchronized.

What happens with sensor data if several TRI-KA measuring devices are used on the same PV system?

Both devices – TRI-KA and TRI-SEN – are respectively coupled with each other so that the sensor data can only be received by the allocated TRI-KA. If one device must be replaced, the devices can subsequently be re-coded with each other.

Must further accessories be purchased for the complete TRI-KA set?

The complete set includes all measuring devices with accessories which are necessary for immediate measurement, plus PC software for the evaluation of measuring data. Unpack, switch on and measure!

In addition to irradiation and module temperature, TRI-SEN also measures the inclination of the sensor. Is this value required for STC calculation?

The sensor’s angle of inclination is only used as an informational value in the logs of whether the sensor had the same inclination as the measured string during TRI-KA measurements. For properly measuring the irradiation, the sensor must have the same orientation and inclination as the string (module) to be measured.

Is it possible to also display and manage in the TRI-KA II the measuring data of the predecessor model TRI-KA I?

In the current PC software, the measuring data of TRI-KA I can be read in and managed. Measurements with TRI-KA I can be additionally stored on the SD card of TRI-KA II and downloaded from storage in the measuring device. Parallel operation of both generations is thus possible with one PC software.

Why does the TRI-SEN sensor have one mono- and one poly-crystalline reference cell for measuring the irradiation?

According to the standard EN 60904, the reference cell must have the same spectral properties as the module to be measured. Selection of the reference cell is effected via the selected module from the TRI-KA module database in the measuring device.

Why does TRI-SEN not have any reference cells with thin-layer technologies?

The standard EN 61829 (Measuring the Current/Voltage Characteristic at the Place of Use) only refers to the STC calculation of crystalline modules. Currently, there is no basis of the standard for any calculation of measured data from thin-layer technologies at STC conditions. Under certain conditions, TRI-KA may be used to electrically measure modules with thin-layer technology. Please consult TRITEC in this respect.

What is the reason for the information “filling factor“ with regard to measurements?

The filling factor describes the quality of solar cells. It is defined as the quotient of MPP power and the theoretically maximum power resulting from the product of short-circuit current and open circuit voltage. The curve of the measured characteristic and the filling factor calculated from the measured data can be used to determine additional series resistances, e.g. due to wiring (wrong cross sections), corroded plug connections, etc. on the module or in the string respectively.

Why is an infrared sensor used with TRI-KA for temperature measurements?

An infrared sensor can record faster and more precisely an average value of the module temperatures on the module or string to be measured. Wire-bound sensors must be fastened, for the majority, on the back of the module. With this measuring process, the module temperature can only be measured at this one place in the string and with a time delay (sensor must first pick up the temperature).

On the SD card, TRI-KA has a module database of over 6,000 modules. What happens if a module does not exist in the database?

TRI-KA can nonetheless be used for measurements. The missing module can be manually added to the PC software and subsequently allocated to the respective TRI-KA measurements. If information is provided to TRITEC, the missing module will be added to the master database.

Are updates of the module database and also updates of the PC software and the TRI-KA firmware free of charge?

Yes! All updates can be downloaded free of charge from our website www.tri-ka.com or via the automatic update function in the PC software.

Are sample curves available for the TRI-KA device, with a description of the causes of error?

A case study provides some sample curves with a description of the cause of error and possible solutions. You can download them free of charge from our website www.tri-ka.com

TRI-KA stores the measured data on an SD card. Can different SD cards be used for the measuring device?

Yes! However, the SD cards must first be formatted in the measuring device to the TRI-KA format and then, the module database can be stored in the PC software on the card. Thus, different SD cards may be used e.g. for the different PV systems.

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Head of Product Management

Simon Schmidt

+41 61 264 00 25

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Find more information on TRI-KA, references, software updates etc. at www.tri-ka.com