I have an optical pulse sensor connected to an Emonpi and recording the pulses from the generation meter connected directly to my inverter. Each day the accumulated kWh recorded in emoncms exceed the values recorded by the inverter and shown on its integrated display to the tune of around 1kWh. Can anyone offer a simple explanation? I had been manually recording outputs from the inverter and uploading them to pvoutput.org and I had hoped that getting the Emonpi would allow me to automate this process but now I don't know which figure to trust.
Why do pulse sensor readings from my generation meter differ from the daily outputs recorded on my inverter display?
Submitted by Toberwine on Sat, 22/08/2015 - 08:47»
Re: Why do pulse sensor readings from my generation meter differ from the daily outputs recorded on my inverter display?
Have you looked at the specs for your generation meter, in particular what each pulse represents.
Most meters we have seen pulse at 1 watt/hour, and hopefully yours will do the same, however it's worth checking.
If its something different, then you will need to add a calibration process to the feed to ensure it's accuracy.
Paul
Re: Why do pulse sensor readings from my generation meter differ from the daily outputs recorded on my inverter display?
Hi Paul, yes I have. The anomaly is only around 1%. I'm not sure if it's the same every day as the inverter round to the nearest kW. If it is a bit of calibration would fix it but it still wouldn't tell me which is "right", the pulses or the inverter measurement. I will take some daily readings from the meter to see what that tells me.
Watch this space!
Re: Why do pulse sensor readings from my generation meter differ from the daily outputs recorded on my inverter display?
What does the kWH reading from the meter say? Does it agree with your pulse counter, or does it agree with the inverter's display?
Re: Why do pulse sensor readings from my generation meter differ from the daily outputs recorded on my inverter display?
Hi dBC, I'll have to take some overnight readings from the meter to compare.
Re: Why do pulse sensor readings from my generation meter differ from the daily outputs recorded on my inverter display?
Robert or dBC - Can the pulse sensor be relied on to hold the input high in between pulses? or could extra pulses be due to a floating input as per the Emontx V3 showing pulse reading thread? as I couldn't find the pullup on the emonPi either.
Paul
Re: Why do pulse sensor readings from my generation meter differ from the daily outputs recorded on my inverter display?
I don't know, I haven't got a pulse sensor, but as the documentation page says "Pulse Output: TTL" I would put money on the internal pull-up not being needed by that sensor. But I don't think it will matter if the internal pull-up is left on. The minimum value of the pull-up resistor is 20 kΩ (per the Atmel data sheet) and a standard TTL output should sink well in excess of 0.165 mA.
dBC's change works for me. Before, the pulse count was susceptible to running my finger over the back of the RJ45, now it isn't. When I saw this thread, I did wonder whether it could be the same problem.
Re: Why do pulse sensor readings from my generation meter differ from the daily outputs recorded on my inverter display?
Andrew, see Appendix A - http://openenergymonitor.org/emon/buildingblocks/opticalpulsesensor
Have you a Actaris ace9000 or Xil XLA12 meter?
Paul
Re: Why do pulse sensor readings from my generation meter differ from the daily outputs recorded on my inverter display?
Thanks Paul. I got my Emonpi earlier this month and I followed through all those instructions in the appendix. It works fine, I'm just perplexed about the difference in the readings.
Re: Why do pulse sensor readings from my generation meter differ from the daily outputs recorded on my inverter display?
Yes, but the readings should not be significantly different. Can you confirm which generation meter you have pls.
Paul
Re: Why do pulse sensor readings from my generation meter differ from the daily outputs recorded on my inverter display?
Paul,
It's a Landis & Gyr 5219J.
One thing I have noticed is that the optical sensor tell tale LED glows steadily when there is no output from the inverter, ie. it is dark.
Re: Why do pulse sensor readings from my generation meter differ from the daily outputs recorded on my inverter display?
Well I have some interesting early results. A but patchy since the Emonpi went down on Saturday and I had to reboot Sunday, and the grid was off from 930am - 5pm on Tuesday for scheduled maintenance.
Sunday gen meter reading 67.17kWh, Optical pulse sensor reading no data. Inverter reading 65kWh.
Monday gen meter reading 71.35kWh. Pulse sensor reading 71.0kWh. Inverter reading 69kWh.
Tuesday gen meter reading 32.62kWh. Pulse sensor reading 32.6kWh. Inverter reading 31kWh.
So it appears that the inverter is under-recording output by around 3%. This could explain some anomalies I've had where my combined own-usage and export (derived from my electricity bills and utility company online monitoring service) have exceeded my generation (using data from my inverter)!