No reading from my RJ45 Encapsulated DS18B20 temperature sensor


I am a newby and I have just setup my EmonBase and EmonTX V3.

I am getting readings from the 2 CT Sensors I have plugged in (see screenshot) but I am not getting any readings from the RJ45 Encapsulated DS18B20 temperature sensor. I have the 3 phase firmware running - it was pre-installed when I got it.

What might I be missing as I have not found much documentation on how to setup this wired temperature sensor?

Thanks in advance for any help!

Best Wishes,

were all sensors connected prior booting up the emontx ? I looks for sensors at boot, not afterwards if I remember well

Hi Eric,

Thanks for the super fast response - I just restarted it (i.e. unplug and then re plugin the power) and it did not make a difference. I also pressed the reset button on the emonTx and it did not make a difference…


There’s no setting up required - other than the resolution, which should not need to be changed. And as Eric says, plug it in before power-up/resetting.

“300” means the temperature is out of range.
“301” means the sensor has not been detected. That value is loaded at start-up and overwritten when the sensor sends a temperature. So with only one sensor, that’s OK for nos.2-6.
“302” means the sensor has been powered up but not asked to read the temperature, but it has been asked to send the temperature back. It’s likely to mean an intermittent connection.

I have a sensor like that - the RJ45 connector was either not crimped properly, or it’s the wrong one for the wire used, or the wire used is wrong for the connector. Solved temporarily by pressing down on the contacts with the back of a knife blade as I don’t own the correct tool. Make sure the plug is inserted fully, and if it was, you could try that. Otherwise, contact The Shop.

Hi Robert,

Thanks a lot for your very informative response. I tried everything you suggested and it does not make a difference to the readings. In fact it now always shows 301. I will take your advice and contact the shop.

Best wishes,