Calibration VCAL ICAL PHASECAL
This guide covers calibration of AC factors VCAL ICAL PHASECAL used with RPICT series.
Overview
For AC related measures there are 3 coefficients. 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 although 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 coefficients 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.
Note it is important to ensure the reference device is giving True RMS. This is what the RPICT does and calibrating against a non-true-rms might not be the best idea.
Also make sure the multimeter is set to AC when measuring the installation voltage and current.
Changing Calibration Coefficient in the web tool
See further down this page for how to calculate the new calibration value. This section only explains how to modify them in the web tool.
To modify the calibration value you can either edit the configuration file manually or use the web tool as explained below.
Starting the web tool is explained here.
Go to the Full Configuration page.
Load the config with the Load from device button.
Go to the section related with the target card. Master or slave.
Set the CT type or Voltage type as Custom.
Modify the value to the desired one.
Use the Send to device button to apply the change.
Changing Calibration Coefficient from command line
See further down this page for how to calculate the new calibration value. This section only explains how to modify them with command line.
Dump the config with
lcl-rpict-config.py -a
Then open the file located in /tmp/rpict.conf.
nano /tmp/rpict.conf
In this file you will find a line with KCAL. The KCAL parameter contains both VCAL and ICAL. See the section below to find which one is which.
Modify the relevant KCAL entry.
Close nano with Ctrl X.
Load the config in the device with
lcl-rpict-config.py -a -w /tmp/rpict.conf
Voltage VCAL
-1-
Open your config as explained above either from the web tool or command line.
Take a note of the VCAL value currently setup in the configuration. Say
this is VCAL = 545.0 for our example here.
-2-
Connect the voltage sensor (ac/ac or zmpt) 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 Vrpict = 269.5V.
To achieve this you can just read the serial port with the lcl-run command or any other program you might have.
lcl-run
-3-
Use the multimeter to read the real voltage value. Say in our case the multimeter shows Vreal = 245.6V.
-4-
Calculate the new VCAL as such
newVCAL = VCAL*Vreal/Vrpict
For us here this is newVCAL = 545.0\*245.6/269.5 = 478.44V.
-5-
Enter the newVCAL value in the configuration as explained above.
Current ICAL
Current is generally calibrated against a "Clamp Meter" or a Multimeter set as Amps AC.
Calibrating current is the same procedure as explained for Voltage above. The new calibration formulae is
newICAL = ICAL*Ireal/Irpict
Ireal being the current measured by the trusted multimeter. Irpict being the current measured initially by the RPICT board.
PHASECAL
In general Phasecal does not need to be any different from 0. Giving any other value to PhaseCal will shift the voltage signal against the current signal to compute power. In general there is no need to change phasecal from its default value 0.
There are 2 method for ajusting phasecal.
Resistive Load Method
-1-
Make sure PHASECAL is set to 0 in the configuration.
-2-
Configure the board to output Power Factor.
-3-
Use a purely resistive load like a radiator or a kettle.
-4-
Adjust Phasecal in the configuration until PowerFactor equal to 1 or slightly smaller. We recommend iterating in steps of 1. If PhaseCal = 0 then try -1 +1 -2 +2 etc until PowerFactor reaches a value close to 1. Do not set any value above +10 or -10 for phasecal.
Real Power Comparison method
If you have another system measuring Active Power (Real Power) this can be used.
-1-
Calibrate both Voltage and Current as explained above.
-2-
Make sure Real Power is in the output.
-3-
Apply a load and measure it with both the external system and the RPICT board.
-4-
Adjust phasecal by increment of 1. Start with -1 then +1 -2 + 2 and so on. Until you get the 2 real power matching as close as possible. Do not set any value above +10 or -10 for phasecal.
KCAL
As mentioned above KCAL parameters is an array containing both ICAL and VCAL. We show here below the location of each channel for each board.
Value with a 1. are placeholder and do not have any action on the device.
RPICT3T1 & RPIZ_CT3T1
kcal = 83.33 1. 1. 83.33 1. 1. 1. 83.33
kcal = ct1 1. 1. ct2 1. 1. 1. ct3
RPICT3V1 & RPIZ_CT3V1
kcal = 83.33 83.33 83.33 1. 1. 1. 1. 545.0
kcal = ct1 ct2 ct3 1. 1. 1. 1. V1
RPICT7V1 all versions
kcal = 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 560.0 83.33 83.33 83.33 83.33 83.33 83.33 83.33
kcal = 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 V1 ct7 ct6 ct5 ct4 ct3 ct2 ct1
RPICT7V1 all versions with firmware V4 & V5
kcal = 560.0 83.33 83.33 83.33 83.33 83.33 83.33 83.33 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
kcal = V1 ct7 ct6 ct5 ct4 ct3 ct2 ct1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
RPICT8 all versions
kcal = 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 83.33 83.33 83.33 83.33 83.33 83.33 83.33 83.33
kcal = 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 ct8 ct7 ct6 ct5 ct4 ct3 ct2 ct1
RPICT8 all versions with firmware V4 & V5
kcal = 83.33 83.33 83.33 83.33 83.33 83.33 83.33 83.33 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
kcal = ct8 ct7 ct6 ct5 ct4 ct3 ct2 ct1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
RPICT4V3 all versions
Also for RPIZ_CT4V3T1 and RPIZ_CT4V3T2
kcal = 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 560.0 560.0 560.0 1 83.33 83.33 83.33 83.33
kcal = 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 V3 V2 V1 1 ct4 ct3 ct2 ct1
RPICT4V3 all versions with firmware V4 & V5
Also for RPIZ_CT4V3T1 and RPIZ_CT4V3T2
kcal = 560.0 560.0 560.0 1 83.33 83.33 83.33 83.33 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
kcal = V3 V2 V1 1 ct4 ct3 ct2 ct1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1