Power Monitoring Calibration - FengtianGu/Sonoff-Tasmota GitHub Wiki

You might need to calibrate your power monitoring device as correct measurements are influenced by hardware and timing differences.

What you need

Your power monitoring capable device flashed with Tasmota and configured to a correct module/template that supports power monitoring
Calibrated multimeter (AC capable).
A resistive load device (we use a 60 W incandescent light bulb in the example).
- Resistive load device is any device which draws a constant amount of power such as an incadescent or halogen light bulb (best choice since their power draw is declared on them). Electric kettle or electric heater can also be used but it is recommended to use a power meter in conjunction since the load could vary.
- Do not use switch mode driven devices such as LED lamps, computer equipment or inductive/capacitive devices such as motors!
(optional) Calibrated power meter (aka Kill A Watt).

Step 1

Connect the light bulb to your device.

(optional) Plug your device into the power meter.

Turn power on and wait a few seconds for the power metering to settle on a stable power reading.

Step 2

Open the web UI to your device in one window and open another window to that same devices Console.

Step 3

Verify the Power reading in the web UI (optionally with the power meter as well) for the expected 60 W and if needed change the power offset with command:
PowerSet 60.0
(if you're using something with different power draw enter the appropriate number)

Step 4

Verify the Voltage reading with the multimeter and if needed change the voltage offset in V with command:
VoltageSet 235.5
(235.5 would be replaced with your measurement which varies depending on the electrical standards and your electrical grid)

Step 5

Verify the Current reading by calculating current value (amperage) using formula P_(W)/I_(V)=I_(A) and if needed change the current offset in mA (mA=A*1000) with command:
CurrentSet 254.777
(instead of 254.777 enter your calculation value of A multiplied by 1000)

Step 6

Confirm the validity of your calibration process checking Power Factor from the WebUI which should be 1.00 or as close as possible to 1.00 (In theory resistive loads will always provide a Power Factor of 1.00). If that is not the case, we recommend to repeat the calibration process and make sure everything was done correctly.

Current calculation:

P/U=I
W(atts)/(V)oltage=(A)mperes

watts/volts *1000=CurrentSet value
(60.0/235.5)*1000=254.777

End

Congratulations!!! Your device can now reliably monitor power consumption!

Script for automatic calibration

Tampermonkey script submitted by @yuuya45