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Homework Help: How to measure the intensity of Infra red

  1. Oct 22, 2008 #1
    Im investigating how infra red is affected in different areas e.g at home, out side, in the dark or in light. To do this i have made a circuit with a photodiode from the company rapid. The problem is that the photodiode is operating as just a switch, saying if the infrared is on or off so i am not able to measure how strong or weak, the beam of infra red is.
    At the moment, im thinking of having a phototransisor or infrared transistor to measure the intensity insead of a photodiode but am not sure if it will work with infra red? can anyone help?


  2. jcsd
  3. Oct 22, 2008 #2


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    Staff Emeritus
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    Homework Helper

    Welcome to PF.

    A photodiode can work for this, but it depends on the circuit you use it with. It also depends on what infrared wavelengths you are trying to measure. If the infrared you want to measure is outside the detectable range of the photodiode, then all bets are off.

    Can you describe (or better, provide a drawing of) the circuit you have?



    p.s. Is this for a class assignment or homework? If not, I can inquire about getting the question moved to a more appropriate area here at PF.
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