OPT3001: OPT3101 Internal Cross talk Measurement

Pengsheng,

 I will always respond to you, sometimes I need to research the question in order to provide the correct and appropriate answer. Sorry for the delay.

After a full calibration, Place blackout tape over the photodiode, start Latte, click start capture. With the photodiode covered read the mean ambient level in the lower left hand corner of the Latte window. The number of codes you are measureing for amplidude is the crosstalk noise level after calibration. This technique will use the internal TX and RX circuits, the routing on the PCB, the emitter and pohotodiode as a complete system. However it will not see a reflection. due to the blackout. With the entire circuit working you can then see the noise in your circuit. If this noise is higher the >200 codes then you will have a high noise floor preventing you from reveiving weak reflections. My EVM has an amplitude of 30 codes after calibration with the photodiode blacked out. This would be a very good noise level for accurate distant measurements.  

Remember black tape is not a very good blackout for IR. If using black electrical tape put 2 layers of tape over the photodiode. I use 99% black out tape (not black electrical tape) in two layers.

If you cover both the emitter and photodiode with blackout tape, you may get a lower noise level, but this is wrong because you may be blocking indirect IR from the emitter that will be there when making an actual measurement. This would lead you to believe that you have a lower noise level than you may have in actual use. 

Pengsheng,

 Yes 

Pengsheng,

  Then you need to do a complete calibration. Some of the corrections during the calibration will adjust for crosstalk and lower this value.