Monitoring output current using a Witty Pi 4 on a Rapsberry Pi 4

Hello,

I try to monitor the output current trough the Witty Pi 4 on a Raspberry Pi 4.

The system is 12V powered using a bench power supply. Power is applied on the VIN connector (XH2.54).

The bench power supply gives me 12V and 0.240A when the Raspberry Pi is idle.

Here are some results monitoring the current at 10Hz:

0.170 0.380 0.170 0.210 0.170 0.360 0.340 0.120 0.320 0.340 0.100 0.080 0.060 0.100 0.320 0.120 0.340 0.080 0.080 0.380 0.250 0.360 0.020 0.080 0.080 0.150 0.100 0.120 0.100 0.040 0.120 0.230 0.150 0.170 0.320 0.100 0.230 0.100 0.380 0.230 0.100 0.340 0.150 0.100 0.250 0.190 0.100 0.100 0.320 0.300 

Is it normal that the values fluctuate so greatly?

Can the output current monitoring be improved?

Here is the Python script I use:

import smbus
from time import sleep

WITTY_PI_I2C_ADDRESS = 0x08

class WittyPi():

    def __init__(self):

        self.i2c_bus = smbus.SMBus(1)

        self.firmware_id = 0
        self.input_voltage = 0.0
        self.output_voltage = 0.0
        self.power_mode = 0
        self.firmware_revision = 0

        self.get_firmware_id()
        self.get_input_voltage()
        self.get_output_voltage()
        self.get_output_current()
        self.get_power_mode()
        self.get_firmware_revision()

    def get_firmware_id(self):

        self.firmware_id = self.read_register(0x00)

    def get_input_voltage(self):

        self.input_voltage = self.read_register(0x01) + self.read_register(0x02) / 100

    def get_output_voltage(self):

        self.output_voltage = self.read_register(0x03) + self.read_register(0x04) / 100

    def get_output_current(self):

        self.output_current = self.read_register(0x05) + self.read_register(0x06) / 100

    def get_power_mode(self):

        self.power_mode = self.read_register(0x07)

    def get_firmware_revision(self):

        self.firmware_revision = self.read_register(0x12)

    def read_register(self, register):

        try:

            data = self.i2c_bus.read_byte_data(WITTY_PI_I2C_ADDRESS, register)

        except OSError as e:

            data = None

        return data

    def __str__(self):

        s = 'Witty Pi\n'

        s+= f'  Firmware ID: {self.firmware_id:02X}\n'
        s+= f'  Firmware revision: {self.firmware_revision}\n'
        s+= f'  Input voltage: {self.input_voltage:.3f}V\n'
        s+= f'  Output voltage: {self.output_voltage:.3f}V\n'
        s+= f'  Output current: {self.output_current:.3f}A\n'
        s+= '  Power mode: ' + ('LDO regulator' if self.power_mode == 1 else '5V USB') + '\n'

        return s

def main():

    witty_pi = WittyPi()

    for i in range(0,50):
        witty_pi.get_output_current()
        print(f'{witty_pi.output_current:.3f} ', end='')
        sleep(0.1)

if __name__ == '__main__':

    main()

Thank you