Hi All,
I’m new to open energy and have just ordered by first hardware from the shop for my heatpump.
Sorry if this is a really simple one to start off with but in the mean time i wanted to get some data pushed to the emoncms.org to have a play with. My issue is the data is irregular from a power meter and only sends data when the value changes. When displayed in the feed or under “my electric” any periods with no change, for example when its not running, do not show this period. When its not running it pulls 32W but this doesn’t change so the data does not get sent to emoncms.org.
Is there something i should have set up so it still uses the current value every 10s or something?
I have the log to feed process set as PHPTimeseries.
Any help greatly appreciated.
Hello @roscoegray, thanks for the heatpump monitor order! 
Emoncms.org doesnt really support irregular data in the way you describe, can you change the way your meter posts data or have an intermediary script to change it to a regular fixed interval? What kind of meter are you currently using, how are you reading and posting the data?
Hi @TrystanLea
Currently using just a cheap owl energy monitor (CM119-102) and then picking up the data using a USB transceiver (RFXtrx433E) that is plugged in to a Vera Pro. The Alternate UI has the option to log data to emoncms.org as standard so just using that feature.
I think i will moving to openhab for my home automation so i think i will have more flexibility to manipulate the data with that.
Once i get the heatpump monitor up and running i will be using that for power monitoring anyway so shouldn’t be an issue at that point.
Looking forward to the delivery to get started!
Hi @TrystanLea
So nearly have my heatpump monitor up ready to install, just run into a little issue that I’m a little confused at. The CT power monitoring was reporting values vastly different to what I was expecting, 8KW when expecting 2KW. I had a look at your info on the CT Calibration and changed the following values in the Arduino sketch…
ct1.voltage(0, 262.0, 1.7);
ct1.current(1, 90.9);
ct2.voltage(0, 262.0, 1.7);
ct2.current(2, 90.9);
to…
ct1.voltage(0, 246.5, 1.7);
ct1.current(1, 20.0);
ct2.voltage(0, 246.5, 1.7);
ct2.current(2, 20.0);
I measured my supply voltage and changed the current value to 20 based on the 100Ohm burden resistor. Now seem to be reading a much better values. First I just wanted to check if this is correct and if the 90.9 is an error in the sketch and also to calibrate further could I have some guidance? Can I load one of the one of the demonstration sketches from emonTxFirmware as described on the calibration procedure learn page?
Thanks Again
90.9 is not an error, it is the correct value for the standard emonTx 22 Ω burden. If you change the burden resistor, or the current transformer, the current calibration constant must be changed accordingly. Likewise, if you change from the Ideal UK adapter, or you change the voltage divider ratio, the voltage calibration constant must also be changed.
You’ve obviously seen the calibration procedures, so if you want to get the calibration to be accurate (that is, to within the accuracy of your reference instruments), you should follow those procedures.
There is no need to load a different sketch, you can easily extract the values you want inside your present sketch. I answered this same question only yesterday.
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Thanks @Robert.Wall,
Not long after I posted and after re-reading the calibration procedure it clicked for me and I understood. I uploaded the voltage_and_current.ino sketch and changed the values to get it as close to the correct voltage and current as I could, all seems to be reading as expected now.
I ended up on 20.35 for the current value and the burden resistor supplied with the heatpump monitor kit is 100ohms so that makes sense. I think this is supplied as over the 22ohm as you don’t need the range if using it purely on a heat pump. I did how ever have to up the voltage value to 270 get the correct reading, makes sense again why this was default at 260.
That is good to know for next time that I can extract the values without uploading a different sketch. Thanks!
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The general point is, the accuracy is defined by the components used, all are subject to manufacturing tolerances. Calibration takes out that initial uncertainty in their collective values. If you want to maintain the accuracy of the measurements, you would need to check and calibrate at intervals (every one or two years probably). And you’d need to have your reference meter calibrated first!
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