Now I'm working with cRIO 9024 and NI 9505 to build a better PID controller. I've downloaded the exmaple given by NI to learn how to build one myself. But suddenly I happen to a problem. I connected a ammeter between motor and NI 9505, then used PWM generator to run the motor and indicated the value returned by Current Sense of NI 9505. Suddenly, I saw the number of the indicator and ammeter were not same. For example, when set to 30% duty cycle, the ammeter showed more or less 9.1mA while Current Sense indicated 25-28, and when 60%, ammeter raised to 13.1 while Current Sense fell to 19-22, I really confused why it happened like this.
And I also saw the current feedback was used in the control loop as PID setpoint, how does it works? If it is not the current pass through the motor, what does it used for? How to use it?
Thank you for all your helps.
Zheng Li
