EmonTx does not show any CT values

Hi everyone,

I have recently bought a emonTx 3.4 + WIFI. It is connected to my own emoncms website (see attached screen captures). Everything went fine during the installation. And some values can be read.
A CT is connected to the main but I can’t see any CT1 CT2 CT3 CT4 values.
I presume that eventhough no CT are connected we should at least read 0W.

Do you know what could cause the fact that not CT values are read?

Thanks for you help!


Welcome, Pierre, to the OEM forum.

Have you looked at the FAQ (Frequently Asked Questions)? There is a link to that at the top of every page.

You will not see anything, unless the c.t. is connected when you power the emonTx. You must connect all the sensors and then power the emonTx - the sensors are only detected as the emonTx starts.

oups you are right, problem partially solved! thanks. I can now read “CT1 detected i1Cal” but the value does not update. I will look for answers in the forum

both my CT lines are now connected.

CT1 detected i1Cal and CT2 detected i2Cal are now shown on emoncms. So, based on the .ino CT1… has been renamed to P1…
I recieve P1 E1 and P2 E2 but their values are 0.

I have probably an issue with my CT lines. I have soldered a jack at the tip as I was using 2CTs with bare connectors.

CT1 & CT2 are the input channels, the result of multiplying the current from the c.t. and the voltage from the a.c. adapter is power, and the power values it sends are P1 & P2. The powers are also accumulated over time to give you the total energy - E1 & E2.

You should connect each c.t. to tip and sleeve of the 3.5 mm connector, there is no connection to the ring.

Which c.t. are you using? If it is not the YHDC SCT-013-000, then your calibration will almost certainly be wrong.

Please fin attached two pictures. Solderings were quickly made for testing :slight_smile:
These two CT used to work at I have used them on my custom energy monitoring device. Basically openenergy monitor arduino code…

Which colours have you soldered together there? The c.t. secondary winding is connected to red and white, the screen is not connected, either at the plug or inside the c.t.

Look at the test report in ‘Learn’, where you will find a picture of the inside of the c.t.

red on red and white on white. I made sure the ground or screen is not connected yes

Do you have a multimeter, that you can check the resistance? Between tip and sleeve, you should read approximately 100 Ω.

And do you have the a.c. adapter connected, because without that, power will read zero even though you have a current.

Yes 100 ohms on both and AC adpater and DC are connected.

Did you buy the emonTx and the ESP8266 together, from the OEM shop?

Do you have a programmer that you could connect to the emonTx instead of the ESP8266?

yes I bought the emonTx and the ESP8266 preprogrammed. And yes I have a programmer. The ESP8266 is embed inside the case. First of all, I suppose I have to unplug the EPS8266 from the UART port inside the case.

I don’t know - I have the old ESP8266 (and the older emonTx) where the ESP8266 plugs into the FTDI programmer port - but as the circuit diagram shows both are connected in parallel, I think it is likely that you must unplug the ESP8266.

Before you do that - you did remove all the power both d.c. and a.c. to be certain that the sketch found the c.t. after you had connected it?

A further thought (I do not know the ESP8266 at all well - so I did not immediately think of this):

What does the “Logs” say at the very beginning. I see this:

2021-08-07T12:45:22.899Z	{"CT1 detected, i1Cal":90.9,"freeram":29904,"srssi":-48,"psent":0,"psuccess":0}
2021-08-07T12:47:29.377Z	{"RFM69CW only Node":15,"freeram":28960,"srssi":-55,"psent":1,"psuccess":0}
2021-08-07T12:47:40.893Z	{"CT3 detected, i3Cal":90.9,"freeram":28240,"srssi":-43,"psent":4,"psuccess":0}
2021-08-07T13:18:42.574Z	{"CT2 detected, i2Cal":90.9,"freeram":28512,"srssi":-39,"psent":1,"psuccess":0}
2021-08-07T13:18:43.624Z	{"CT3 detected, i3Cal":90.9,"freeram":28856,"srssi":-41,"psent":2,"psuccess":0}

If i1Cal etc has been set to zero, that will explain why the power reads zero.

Yes I did that several times.

CT1 detected, i1Cal:90.90
CT2 detected, i2Cal:90.90
AC present

So you DO have a power, but it is small. That is not the same as zero.

So is the real problem - you are not measuring the current (power) that you expect?

AC present

And I am attached to the main power with CT1 P1 E1 and to my solar panels CT2 P2 E2

Those power values must be “noise” picked up by the emonTx. For some reason, the emonTx knows a c.t. is plugged in, but it is not measuring any current. I cannot think why, except that there is a problem with the c.t. connections. Can you check those again please - you did measure between tip and sleeve (in audio terms, Left and Common(ground)? And (silly question I hope) - you did push the plug in all the way?

100 ohms are between the tip and the middle part of the jack (please see my pictures). Is that correct?

Ah - the connections on a 3-pole (stereo) connector are:

The Ring is not used, the connections are to Tip & Sleeve.