Difference between revisions of "Analog setpoint"

Revision as of 14:35, 26 March 2012

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

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

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

Another common voltage range is 0..5V where may be zero reference may be at 2.5 VDC.

Example

Lets assume +/-10V is used as torque reference 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 reference is also a current reference.

Differential signaling

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

• Positive input
• Negative input
• Ground

The actual reference 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.