Current limit with DRV8825 stepper driver and NEMA17 motor

Projects General Guidance
1

Hello,
I am starting a project using Arduino, a stepper motor (NEMA 17HS19-2004S1) and a stepper motor driver (DRV8825).
I am having trouble with the current limit of the motor. I read that for the DRV8825 driver, the current limit can be adjusted using the formula: Imax=2*Vref. My motor datasheet indicates "2.0A per phase" so I turned the driver potentiometer in order to measure Vref=1.0V (between the potentiometer screw and the "ground" pin).
But when I measure the current in one of my motor coils, I read approximately 1A. How is that possible?
When its running, my power supply shows approximately 0.4A, but I read in the DRV8825 documentation that it is not a good indicator of the current in the motor coils.

Detailed characteristics:

  • Power supply: 30V - 10A, which I set on 25V.
  • Motor:
    -- Angle: 1.8°
    -- Precision: 5%
    -- Torque: 59Ncm(83.6oz.in)
    -- Nominal current/phase: 2.0A
    -- Phase resistance: 1.4ohms
    -- Tension: 2.8V
  • Inductance: 3.0mH ± 20%(1KHz)

Thanks for your help!

2

What setup did You use when measuring the current in the coil?
A little wiring and a link to the data sheet of the instrument, please.
There are many ways to get faulty readings for signals like this.

3

Thank you for your answer.
I plugged my ampermetre between the DRV8825 "A2" pin and the corresponding "A2" motor wire (with series connection).
The DRV8825 is from Polulu.

4

AC or DC current?
What kind of meter?