How do I calibrate radiometric light intensity?
If one wishes to perform a photometric measurement, such as illuminance, use the PS-2177 PASPORT LUX Light Sensor, which directly measures illuminance.
If you wish to have a radiometric measurement, then use one of the appropriate thermopile sensors:
In order to measure the irradiance of an object accurately, the peak wavelength should be well within the spectral range of the sensor, which is determined from Wien's Law: Wavelength [nm] = 2.898*10^6 [nm]/[K] / Temperature [K].
None of the PASCO radiometric sensors are calibrated or have integrated diffusers. If you want to measure the irradiance of a light bulb, we recommend that you first find the total radiant power and divide by the appropriate surface area and/or solid angle to obtain the radiometric quantity of interest.
For example, irradiance [W/m^2] is the total power of electromagnetic radiation per unit area of surface. To obtain irradiance at the surface of the bulb, assuming a uniform distribution of light at the diffusive surface of the bulb, divide the total radiant power P by the surface area of the diffuser, A.
Irradiance = P / A
Note: To measure solar irradiance, we do not recommend the PS-2150 PASPORT Broad Spectrum Light because it will saturate at irradiances much less than that of the sun.
If one wants to measure absolute light intensity, we recommend performing a two-point slope calibration:
Procedure (PASCO Capstone software minor modifications required for other data acquisition applications.)
The radiometric system is now calibrated in terms of total radiation power.
To measure illuminance, use the PS-2177 PASPORT LUX Light Sensor instead.
Creation Date: 03/5/2010