Calibration VCAL ICAL PHASECAL

This guide covers calibration of AC factors VCAL ICAL PHASECAL used with RPICT series and Emonwrt3.

Overview

For AC relates measures there are 3 main coefficient. VCAL ICAL and PHASECAL.

These coefficients are set by default at manufacturing time. These are normally good enough to operate straight away and provide a decent reading.

All sensors even all produced identically have minor differences between them. This also applies for the ADC and passive components on the RPICT board. Therefore one may want to adjust the calibration coefficient to get more accurate values.

To achieve this a high quality multimeter or scope will be required. This will be the reference system that we will trust as being right.

Voltage VCAL

-1-

Setup in configuration an approximate value for VCAL. You might just use the default provided to start with. We will use VCAL = 545.0 in our example.

This can be anything but should be relatively close to the expected final value.

-2-

Vrms must be selected as output in the RPICT config (obviously). Connect the ac/ac adaptor to the board to be tested and note the reading of the measured voltage given by the RPICT.

Let's say in our case we get Vmes = 269.5

-3-

Use the multimeter to read the real voltage value. In our case Vreal = 245.6

-4-

Calculate the new VCAL as such

newVCAL = VCAL*Vreal/Vmes

For us here this is newVCAL = 525*245.6/269.5 = 478.44

-5-

Enter the newVCAL value in the configuration.