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OPT3004EVM: OPT3004 reading no linear

Chen Alex1
Expert 2505 points
Part Number: OPT3004EVM

Hi sir

DUT will be placed on the holder and ALS PCB will be installed below the holder.

 When I adjust ALS PCB to LED distance from 9mm to 35m with different LED driving current, the LUX value should be showing linear curve.

however, the 9mm curve LUX value was smaller than 15mm and 15mm curve had saturation(The ALS was set fix Range= 2620.8 lux).

do you have any suggestion?

  • 0
    TI__Mastermind 25845 points

    Hi,

    You would need a controlled experiment to run a test like this - as many factors can effect if not accounted for. What is the expected result of this test? Varying the distance will vary light level so the lines are expected to have offset from each other. Additionally, LED output is not typically linear with current so line would not be expected to be straight. LED temperature may also effect the output level if different between runs. It is also strange that at 9mm (closer to LED) the light level is lower than at 15mm (farther from LED) so something may be off there.

    The easiest way to account for some of these effects is to have a reference lux meter for this test while also ensuring it is run in a dark room with only this LED as the light source. However, placing reference meter and ALS side by side they will not get the same amount of light due to non uniformity in the light level so lux meter would need to be moved once to the OPT location carefully to get the difference between lux meter and OPT light level. Varying the distance to the LED should not be done as this will result in changes in the uniformity - so location of the OPT and light source would need to stay fixed.

    The lux meter process is explained here in section 2.1.3: https://www.ti.com/lit/an/sbea002a/sbea002a.pdf 

    Best,

    Alex

  • 0 in reply to Alex Bhandari-Young
    Expert 2505 points

    Has the shortest working distance for ALS?

    Thanks
  • 0 in reply to Chen Alex1
    TI__Mastermind 25845 points

    There is no shortest working distance. But light level will change with distance.

    Best,

    Alex