Optical sensor reverse reading

[Robert.Wall]

I said - the LED indication and the output state can be different. A search should find the discussion.

Here:

Problem with Optical Pulse sensor

The optical sensor output is not a true TTL output as is claimed, it appears to be an over-driven analogue signal - in that is appears to be linear over a small range. You might be able to see this with a multimeter measuring the output voltage. Also, the operation of the green LED on the sensor isn’t a reliable indication that the emonTx has or hasn’t detected a pulse, due to that pseudo-analogue output again. One thing I do notice is, the single-phase emonTx sketch detects a pulse on the fall…