Electrical Insulation on T200

I’m working on a project with two T200 motors on a USV and I’m having issues with the conductivity sensor I am using for water quality. Are the motors capable of inducing significant magnetic fields or electrical currents in the water to affect the sensors? I see proper results when stationary, but when I run the motor, the value I see jumps up significantly (i.e. from 500 jumps up to 3000 uS/cm). Any thoughts on what could cause this, or how to avoid the problem?


Hi @shawn, the T200 is a sensorless brushless outrunner motor, thus it has both permanent magnets in the rotor, and the stator effectively acts as an electromagnet to drive the rotor. The thruster will certainly have different magnetic properties when on versus off, as well as at different throttle levels.

We have calculated a theoretical back EMF constant of 0.00205 V/rpm for the T200.

Hi @shawn ,

Did you find any proper solution for this problem? Like using the theoretical back EMF constant @kklemens gave you to remove it from the measured value, or isolating the thrusters or sensor somehow?

I’m having the same issue with a curvature sensor (basically a variable resistance connected to a voltage bridge) when it’s in the water with the T200 thrusters.