Would it be possible to log the ac frequency using the emonTx?

[Polsaker]

I am interested in monitoring the output frequency of a generator, could the emontx or the emonpi possibly do that job?

[Robert.Wall]

Certainly.

EmonLibCM makes it available, it simply isn’t normally sent with the rest of the data. Look at the documentation for emonLibCM:

EmonLibCM - Version 2.2.1 (Released 30/10/2021)

EmonLibCM is a Continuous Monitoring alternative to EmonLib. Whereas emonLib repeats, every 5 or 10 s, a sequence of voltage and current measurements in each of the input channels for a short period, normally 200 ms, and then reports the measurements back to the sketch for onwards transmission to (for example) emonCMS; emonLibCM continuously measures in the background the voltage and all the current input channels in turn, calculates a true average quantity for each and then informs the sketch t…

[Polsaker]

Does that require any calibration? I’m getting some negative readings, like -15.54

I just changed the emontx firmware to send EmonLibCM_getLineFrequency() * 1000 as F1, and then I I configured emonhub like this:

   names = MSG, Vrms, P1, P2, P3, P4, E1, E2, E3, E4, T1, T2, T3, pulse, F1
   datacodes = L,h,h,h,h,h,l,l,l,l,h,h,h,L,h
   scales = 1,0.01,1,1,1,1,1,1,1,1,0.01,0.01,0.01,1,0.001
   units = n,V,W,W,W,W,Wh,Wh,Wh,Wh,C,C,C,p,n 
   whitening = 1

[Robert.Wall]

What is your nominal line frequency?

Then multiply that by 1000, and assign it to a signed integer? I think that’s where your problem lies.

[Polsaker]

D’oh. I haven’t touched C in a while. I was overflowing the int probably. Got it working now

Thanks!

[Robert.Wall]

@Polsaker

I was overflowing the int probably.

I’m certain you were - 60 Hz * 1000 > 32767. Had you used an unsigned int decoded as H, then you’d have been OK up to 65.535 Hz. But 3 figures is a bit excessive anyway - I wouldn’t guarantee it to more than two.