Defect on CT3

Hardware emonTx
#1

Hi

i got a Problem with one of my EmonTx. As i tried to calibrate and update the EmonTx Firmware to a 3-phase System, i got strange readings on the CT3 port. I am using the Arduino IDE and the 3-phase example sketch. In my first attempts i used a 2.3 kW water boiler to get some readings, so the current should be at 9-10 A. For this test i connected every CT on the same line, so the current should be the same. However every time i start up the EmonTx (restarting the serial monitor in the Arduino IDE) the current on CT3 is at 130A and falls to 1.5-0.5A after a while. Only when i connect CT1 and CT2 as well, this malfunction doesn’t appear but then readings on CT3 are still wrong. (5A at CT3 and 9A at CT1 and CT2)

I made 3 measurements:File-Upload.net - Datei nicht gefunden
Measurement 1: only CT1 and CT3 are connected
Measurement 2: CT1, CT2 and CT3 connected
Measurement 3: CT3 and CT4 connected, water boiler turned off and on in between

With the second EmonTx i bought, it works perfectly well. So i assume this must be an hardware issue.

My question is now, is there a defect on the CT3 port and do i have to get a new EmonTx?
Or do i just have to always use CT1 and CT2 as well for my measurement? Then i would calibrate the CT3 port so that it would meet the 9A readings of the other CTs, but i dont know if there will be a problem when i go to higher loads.

(Sorry for the file-upload link, i dont know how to activate the file attachment for new users)

#2

Sorry to hear you think there’s a problem with your emonTx. I don’t look at external sites, but you should now be able to upload a file here. (I’ve upgraded your account.)

Before I tell you to contact the shop for a replacement, can you load the basic single-phase sketch and test again with 3 CTs on the same cable? If you still cannot get nearly the same current from each channel, even when you swap the CTs around, then the emonTx is definitely faulty and you need to contact support for a replacement.

#3

Thank you for your reply and upgrading my account.
With the basic sketch i still get strange readings from the CT3 channel, even when i swap the cts.
The CT3 channel shows a power consumption of 15kW at startup an remains at this value, even if i turn on or turn off the water boiler. The other channels show correct readings at 2.3kW.
I will contact the support for further help.

#4

Thanks for getting in touch, I’ve organised a replacement. It will be shipped tomorrow.

Very sorry for the hassle.