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EmonTx/emonESP data format


(Kebab Bob) #1

I have emonbase set up with esp8266 and transmitting data to my mqtt server. What I am wondering however is what is exactly in the data? The current clamps (CT[1-4]) look like Watts to me, but what is the VRMS? Is it voltage*1000 or something like that? That doesn’t make complete sense to me, so that’s why I’m asking. I look forward to your response.

I’ve googled around and browsed the help sections a lot but couldn’t find what I’m looking for. I’m using the AC-AC power supply supplied with emonbase.


(Greebo) #2

Do you mean an EmonTx with ESP8266? I didn’t think the EmonBase had any clamp inputs…


(Kebab Bob) #3

Yup, meant EmonTx… :slight_smile:

[edited title from “Emonbase data format” to “EmonTx/emonESP data format” - @pb66]


(Robert Wall) #4

In that case, you need to look in the sketch running in the emonTx. Power will be in watts, the voltage is probably in centivolts :open_mouth: (voltage ×100) in order to preserve two decimal places when truncated to and transmitted as an integer via radio, and the same value is sent by the serial output, which is probably what you’re looking at.


(Kebab Bob) #5

Assuming centivolts and dividing by 100 I get these readings…

Seems a bit strange, but I haven’t double checked my line voltage with a multimeter. I have 3 phases, 230v each.


(Robert Wall) #6

That’s in the right ball-park, it’s responding to the load so it’s not far off. Where is your a.c. reference coming from - because not all a.c. adapters give the same output voltage, and that will change the calibration. You need to go through the calibration procedure for the emonTx. See Learn → Electricity Monitoring → Current & Voltage → Calibration Procedure.


(Kebab Bob) #7

AC reference is coming from the AC adapter I got with emontx. This is data my esp8266 sends over mqtt, stored in influxdb and displayed via grafana.

I’m not using emonhub anymore, my pi SD card died on me and I already had all the other services running in the cloud.

I’ll check the calibration procedure out, thanks for the tip.


(Robert Wall) #8

I’ve just noticed you mention 3 phases. If you’re using the 3-phase PLL sketch, then follow the calibration instructions in the documentation for that.

And note: the 3 a.c. adapters from the shop all require different calibration constants.