# Optical sensor reverse reading **URL:** \ **Category:** Emoncms\ **Tags:** emontx\ **Created:** [23 February 2019 13:02 UTC](https://community.openenergymonitor.org/t/optical-sensor-reverse-reading/10203 "2019-02-23T13:02:59Z")\ **Posts on this page:** 1\ **Showing post:** 9
**Author:** ![Robert.Wall](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/robert.wall/32/38246_2.png) [@Robert.Wall](https://community.openenergymonitor.org/u/Robert.Wall)\ **Post date:** [23 February 2019 15:56 UTC](https://community.openenergymonitor.org/t/optical-sensor-reverse-reading/10203/9 "2019-02-23T15:56:19Z")
I said - the LED indication and the output state can be different. A search should find the discussion. Here: > [@Problem with Optical Pulse sensor](https://community.openenergymonitor.org/t/problem-with-optical-pulse-sensor/9167/2): > > 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… --- _[View the full topic](https://community.openenergymonitor.org/t/optical-sensor-reverse-reading/10203)._