The QSPAR PAR sensor consists of a handheld display unit and matched cosine corrected, large surface area quantum sensor head containing a special high grade photocell filtered for light falling into the 400 - 700nm (PAR) waveband. The quantum sensor head is fully sealed and therefore weatherproof allowing the sensor head to be positioned indefinitely in exposed positions. The QSPAR sensor has been calibrated under open-sky conditions against reference pyranometers and hence referred to the World Radiometric Reference. The linearity of response is excellent with a maximum deviation of 1% up to levels of 3000 watts/m² (greater than normal solar irradiance).

The display unit is matched to the quantum sensor head supplied ensuring correct calibration. The µmol m^-2 s^-1 calibrated value from the sensor is displayed on the LCD display. 3 measurement ranges allow maximum sensitivity from 0 - 2000 µmol m^-2 s^-1. A 0 - 2v analogue output allows measured PAR values to be plotted on a suitable recording device. The QSPAR light meter is intended to be used primarily as a calibration tool for Hansatech Instruments light sources. The instrument is powered by a single PP3 battery.