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OPT101 - to measure solar irradiance

Anith Krishnan
Prodigy 10 points
Other Parts Discussed in Thread: OPT101

Hi, I would like to know whether OPT101 can be used to measure solar irradiance up to 1000 watts per meter sq.

If yes, please give details.

  • 0
    TI__Genius 14825 points
    Hello,

    The OPT101 has a photosensitive surface that is 2.29 x 2.29mm square and an output voltage of 0.45 V/uW.

    To calculate the amount of power on the die surface, I did the following: 1000 Watts / 1 m^2 * 0.0000052411 m^2 = 5.2441mW.

    To calculate the output voltage at full power, I did this: 5.2441mW * .45V/uW = 2359.845 V. Since the output of the device is limited by the power supply which can be at most 36V, the device won't work as-is, however there is an option to change the gain of the device with external resistors and capacitors. On page 9 of the OPT101 data sheet, using a 50kOhm resistor and a 56pF cap will give you a gain of 0.05, which brings that 2359V down to 117V. Mathematically we can see that using a 15kOhm resistor (and some capacitor) will give us a gain of 0.015, which brings the maximum voltage output to 35.4V, which is within the output range of the OPT101.

    While this works mathematically, I don't know how well the device will perform under these conditions.

    Would it be possible to put neutral density filters on top of the device to cut the power down? I believe cutting the light down to 1% transmission would reduce the power by 100, which in turn would reduce the expected output voltage from 2359V to 23.59V.

    Please feel free to correct my assumptions in my math if you find any of it wrong, and let me know if you have any further questions.

    Jason Bridgmon
  • 0 in reply to Jason Bridgmon
    Intellectual 370 points

    Hi Jason,

    I need to measure solar radiation up to 1000 W/m^2, I did my calculations and are similars to yours. See the PDF. 8640.Calculations.pdf

    How I can get the value of capacitor required? perhaps extrapolating the values given in the data sheet tables?

    C_ext=79 - 23/50* R_ext, [R_ext]=kOhm, [C_ext]=pF; this is extrapolating the values in the figure 4 page 9 data sheet.

    In my case the capacitors required are 78 pF

    Is right what I've done? the OPT101 will work for this application?

    Thanks!

  • 0 in reply to Fernando Liozzi
    TI__Genius 14825 points
    I've forwarded this along to our optical team and they should be able to assist you with component selection.

    Thanks!
  • 0 in reply to Jason Bridgmon
    Intellectual 370 points

    Hi Jason, 

    Thanks!, i wait for help.

    Best regards,

    Fernando.

  • 0 in reply to Jason Bridgmon
    Intellectual 370 points

    Hi Jason,

    I receive this link from TI 

    I assume that is the help that the optical technical team sent me, in the page 13 it is shown how to calculate the capacitor. better I will study this document and consult doubts. Thank you for the support.

    Best regards,

    Fernando.