Analog setpoint
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.
 | In typical servo drive, there are ANAIN+ and ANAIN- pins. Setpoint voltage is measured from the difference of voltage potentials between ANAIN+ and ANAIN-. Both ANAIN inputs must always lie within +/-12V from GND (meaning that controller's zero voltage reference, i.e. GND must be connected to the GND if drive to prevent voltage potentials from floating. |
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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