Measuring thruster current with WCS1800

[abdulmuqtadir]

Hi Folks,
I am using WCS1800 current sensors to read the current consumption by one thruster, its range is upto 35A for DC currents so it is in our working range 1A/66mV. It is working almost accurate as I have tested with a 5S Li-In battery and battery-charger given by Bluerobotics itself, the current value for charging which display on LCD of charger exactly matches with my sensor output, so I found it is perfectly calibrated. But the same sensor If I am using to measure the current consumption of T200 then I am getting erraneous value and that too around 50% error. Anyone please can help me out to find out the issue behind this. I think it was EMI or RFI from battery, so I made my thruster ESC apart from battery around 2 mts disthance, but still I am facing the same issue. Or if this issue is because the switching process happening inside the ESC or anything else.

Thanks in advance

[rjehangir (Rusty)]

Abdul,

The thruster speed controller pulses power to the motor as it controls the speed. That happens at a very high rate and if your sensor has a very high measurement bandwidth then it can detect these rapid changes and get noisy or incorrect measurements. If this is the case, I would recommend using a hardware low pass filter to smooth the measurement. For instance, an RC filter with bandwidth of 10 Hz would to a good job of smoothing out this measurement.

The WCS1800 has a bandwidth if 23 kHz so I think this is the cause.

For example, here is the low pass filter we use on our power module for the same reason. The “I_SENSE” connection goes to a microcontroller that reads the measurement.

I hope that helps!

-Rusty