How to calibrate the Voltage Port
For board series RPICT7V1, RICT4V3, RPICT3V1 EmonWRT the voltage should be calibrated against the AC/AC adaptor used. We will explain how to calculate this value here.
Equipment needed
- Any ac voltage measuring device (multimeter, scope).
- AVR programmer
- The board to test must be operational.
Steps
Step 1
Upload the sketch where VCAL is a know value. We will use VCAL = 525 in our example.
This can be anything but should be more or close to what we expect.
Step 2
Connect the AC/ac adaptor and take a reading of the voltage measured. In our case Vmes = 269.5
Step 3
Use the multimeter to read the real voltage value. In our case Vreal = 245.6
Step 4
Calculate the new VCAL as such
newVCAL = VCAL*Vreal/Vmes
For us here this is newVCAL = 525*245.6/269.5 = 478.44
Step 5
Enter the newVCAL value in the sketch and upload to the MCU.