Analog setpoint

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Analog reference signal is ideally clean and precise (blue). However, in problematic cases electromagnetic interference is coupled to the signal (red) causing inaccuracies like noise and offset error/drifting.

Analog setpoint is one of setpoint signal types used in motion control.

The most typical setpoint voltage range is +/-10V where

  • -10V equals the most negative setpoint (-100%)
  • 0V equals zero setpoint
  • 10V equals most positive setpoint (+100%)
  • Any value between is interpolated linearly

Another common voltage range is 0..5V where zero setpoint may be at 2.5 VDC (bias voltage).

Differential signaling[edit | edit source]

Analog setpoint input in target device is typically differential. Differential input requires 3 wires from source device:

  • Positive input
  • Negative input
  • Ground

The actual setpoint value will be calculated from the differential of positive and negative inputs. This eliminates error from ground currents and also reduces sensitivity to EMI noise.

Differential signaling on wikipedia

Example[edit | edit source]

Lets assume +/-10V is used as torque setpoint in VSD drive. In this case 0V equals no torque, and 10V equals 100% of peak torque configured in the drive, 5V equals 50% torque etc.

Peak torque can be configured to drive with GDtool as peak current limit. Torque and current are directly proportional, so torque setpoint is also a current setpoint.

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