I want to calculate the torque of the brushless DC motor for my ornithopter. This is what I wanted to do:
Measure the in-coming current into the motor, measure the out-going current going from the motor to the Electronic Speed Controller (ESC). The difference in current multiplied by the voltage would be the output power. Measure the rpms and then -- (torque = output power / (rad/s)).
I tried this out yesterday. I had two multimeters in current-measuring (mA) modes: One that measures current into the motor, and the other that measures current out of the motor. With this setup, the motor would hardly move. Like the shaft rotates, but not at its full speed -- I mean it makes one complete rotation in like 2 seconds. Then, I got rid of the multimeter that was supposed to measure the current going out of the motor to the speed controller. So, with only one multimeter, the motor did operate at a full speed. However, this way I cannot get the current going out of the motor into my speed controller, and this defeats the purpose of calculating the output power.
So, my question -- is it because of high combined internal resistances of two multimeters, that very little current was going into the motor (causing bizarre 1 revolution in 3 seconds)? Please also let me know if my measurement method is flawed, and suggestions will be greatly appreciated.
Thanks
Measure the in-coming current into the motor, measure the out-going current going from the motor to the Electronic Speed Controller (ESC). The difference in current multiplied by the voltage would be the output power. Measure the rpms and then -- (torque = output power / (rad/s)).
I tried this out yesterday. I had two multimeters in current-measuring (mA) modes: One that measures current into the motor, and the other that measures current out of the motor. With this setup, the motor would hardly move. Like the shaft rotates, but not at its full speed -- I mean it makes one complete rotation in like 2 seconds. Then, I got rid of the multimeter that was supposed to measure the current going out of the motor to the speed controller. So, with only one multimeter, the motor did operate at a full speed. However, this way I cannot get the current going out of the motor into my speed controller, and this defeats the purpose of calculating the output power.
So, my question -- is it because of high combined internal resistances of two multimeters, that very little current was going into the motor (causing bizarre 1 revolution in 3 seconds)? Please also let me know if my measurement method is flawed, and suggestions will be greatly appreciated.
Thanks