Bogus Tx4 vrms values

Finally got my Tx4 working over USB to my emonbase and powered by an emonVS plugged into a nearby 13A socket. Waiting on a USB C to microUSB adapter to move the emonbase over to the same power source.

Noticed this morning that the only feed I’m currently logging from the Tx4 is showing bogus values. Screen shots below are (in order) that of the Tx4, then Tx3 and finally the SDM120 I have on the ASHP. When my supply voltage dives at 00:30 (everything kicking in for the Octopus Go period) the Tx4 goes up!

Hello @greentangerine that is bizarre, were the Vrms readings correct before introducing the USB connection?

Can you try disconnecting and reconnecting the USB connection to see if the voltage readings change, do you still have the readings transmitting over RF in parallel? I know you are trying to sort the missing RF packet data issue discussed on the other thread.

That would also be interesting to hear if that makes any difference. What power adapter are you currently using for the Pi?

I switched off the RF as it didn’t make any sense to keep it transmitting when connected via USB.

The emonbase is powered by a genuine Pi power supply - presumably the one it came with? The power adapter arrived in the post so I shutdown and moved it so that the VS is powering both units.

Screenshoots of Tx4 and SDM below - switch was made just before 12:30 and on coming back up, the Tx4 voltage has dropped.

Thanks @greentangerine can you overlay both feeds on the same graph? how is it looking now that you have a few more hours after the switch?

Thanks, looks like its working well now. What was the raspberry pi power supply used and was it from our shop?

I haven’t noticed the effect you saw before but would be keen to see if I can find a way to replicate it and understand what was happening

I presume you have a ‘standard’ UK domestic single-phase supply, with a single-phase emonVs?

I’m working on a different version of emonLib to Trystan’s, whose is a more direct descendant of emonLibCM – and I’ve never seen nor recorded anything like that. It’s very hard to see what’s happening behind the legend on the graph, but if part of the resistor dropper chain was shorted, the slope of the changes would be multiplied as well as the values - and I’m not sure if that’s the case. Even so, it may well be worth taking the emonVs apart and checking for any debris etc that might have shorted one of the 10 kΩ resistors on the underside of the pcb - the numbers fit: 240 V × 6 ÷ 5 = 288 V - quite close for the values behind the legend.

Yes, single phase Vs. The power supply for my emonbase I presume came with it - has the Pi logo on the top, 2.5A capacity and has been working fine as far as I can tell but as of yesterday unplugged as the Vs is powering it.

The Vs is now mounted on a wall using 3M double side tape - so as long as it is behaving, I’ll leave it be.

The fact that the alleged measured voltage jumped when the real supply voltage dropped significantly is certainly relevant.

The feed voltage is now closely tracking that of the SDM120 and hence so far reliable. I have a voltage logger (now out of calibration but a relic from trying to persuade SSE that their supply voltage was too high - resolved by installing an OptiVolt 100) and that is close to the tx4 now.

Both tx3 devices have the AC/AC supply but both differ and are also a few volts high.

It sounds as if we’ll never know. Maybe if there was a foreign object in there, the act of mounting the emonVs moved it into a safe place.

I hope so - last hour is solid.