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Photo diode output voltage determining factors

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Jul 13, 2011
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what are the factors affecting the output voltage of a photo diode?will distance between light source and photo diode determine its output?

photo diode is not a active sensor
it only changes conductivity, so the output voltage depends on the supply voltage and the resistor used in series

Here is very good technical information of photodiodes.

**broken link removed**


Yes distance will be a factor unless you are using an ideal laser beam which does not pan out over distance.

From what I've been told you need something to focus the light coming in from the transmitting device on to the sensing device.

thanks for the replies........actually i want to measure variations in the range of micrometer.Is it possible by any light sensor?

You mean you want to measure distances of microns? In which case I think you need a coherent light source (laser) and use interference methods.


I think you need a coherent light source (laser) and use interference methods.

I also thought this method.But i have doubt whether laser like coherent sources can be able to sense this much small distances(in microns).i searched in net and the idea i got is it is useful for large distance.I cant find small distance case.what about ur opinion sir?and would u please give me an idea of its sensitivity if we can laser source method?

Besides interferrometry, that can easily measure 0.1 um, triangulation is a possible alternative for short distance. Some optical thickness measurement systems are using the laser optic of to a compact disc drive to sense µm heights. It's a self balancing system, the known actor move gives the measurement.

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