No detector has a constant spectral responsivity under all conditions of use. For instance, the responsivity of photodiode detectors falls off above a certain incident power level due to saturation effects. Full evaluation of a detector requires characterisation of such effects. This information allows the identification of the detector with the best performance for a particular application. Also, a detector to be used for calibration purposes should be fully characterised in order to evaluate the uncertainty of such calibrations.
In all cases the detector under test is compared with a standard detector of known spectral responsivity / quantum efficiency.
300F Monochromator is used to select a narrow wavelength band from a broad band quartz halogen lamp. Wavelength range of monochromator is between 200 - 2000 nm. The wavelength can readily be tuned continuously allowing measurement of spectral responsivity across the wavelength range for which the detector is used.
|Photocurrent measurement range||:||0.1 nA to 1 A|
|Bias voltage||:||+15V to -15V|
|Bias voltage step size||:||100 mV|
|Light Source||:||50 W tungsten halogen lamp|
|Monochromator type||:||Czerny Turner with two holographic gratings and 2nd order filters|
|Wavelength range||:||350 nm to 1600 nm|
|Maximum sample size||:||50 mm|
|Sample holder with manual three axis positioning using knobs|
|Pogo pins or multimeter like probe tips to make contact with the sample|
|Note : PC is not in the scope of supply|
HOLMARC Model: HO-PDC-01 designed for characterisation / measurement of the following detector parameters:
Linearity range : This is the range of incident radiant power levels over which the detector output varies linearly with incident power. (Laser-based methods is used for measuring saturation threshold of a detector).
Spatial non-uniformity of response : The variation of responsivity across the active area of a detector is determined by scanning a small spot of radiation at a selected wavelength over the surface.
Noise Equivalent Power (NEP) : the incident radiant power at a specific wavelength and modulation frequency necessary to produce a signal-tonoise ratio of 1 at the detector output.
Temperature coefficient of response : the variation of responsivity with temperature
Detector shunt resistance : the slope of the current-voltage curve of a photovoltaic detector at zero-volt bias.
Spectral response of a photodiode
Solar cell response at different temperatures