What is the highest frequency in which I can sample AC current data using Emon lib? I’m hoping to package and send the group of obtained samples to a server for analysis. The goal is to create a high resolution identity profile of a device’s energy usage.
Currently I’m transmitting a single data point of energy usage from a particle photon every 10 seconds.
As @calypso_rae pointed out only very recently, the ADC can sample every 104 μs. But to achieve that rate, you cannot use EmonLib, you have to run the ADC continuously and use interrupts to gather and send the data meanwhile. EmonLib uses the slower analogRead( ) function and can achieve about 110 samples per 50 Hz cycle measuring only one quantity, but it cannot do that continuously, it needs time out to average and send the data.
Robert and calypso_rae thanks. What do you mean by “measuring only one quantity”? I’m fine with 110 samples per 50 Hz for now. Might it be possible to do this continuously and buffer the initial group of burst reads, then average and send them out as time allows?
Only one voltage, or one current, not a voltage & current pair to calculate power.
Not really. You can monitor continuously, but you’re severely limited by the amount of memory available to you as a buffer to store the values before you need to do something with them. I’m guessing that you’re looking at the inrush current profile to give you additional data that you will use to recognise the appliance. I suspect you’ll need to do some initial processing to minimise the amount of data you store, otherwise it will be very easy to run out of space.
[Edit]
There’s a nice illustration here: How quick is the emonTx V3? - #7 by dBC
I suspect that if you recorded both positive and negative peak values starting when (say) 10% current was detected and continuing until the peak amplitude stabilised, they you’d have a good profile to match to a table somewhere of ones you recorded for comparison purposes. In this case, you’d have about 30 values, which should be do-able.