92 Mentor MP Short Form Guide
www.controltechniques.com Issue Number: 5
8.3 Menu 3: Speed feedback and speed control
Speed accuracy and resolution
Digital reference resolution
When a preset speed is used the reference resolution is 0.1rpm. Improved resolution
can be obtained by using the precision reference (0.001rpm).
Analog reference resolution
The analog input has a maximum resolution of 14bits plus sign. The resolution of the
reference from analog inputs 2 or 3 is 10bits plus sign.
Analog feedback resolution
The resolution for both Armature voltage and tachogenerator feedback is 10bit plus
sign.
Accuracy
With encoder feedback the absolute speed accuracy depends on the accuracy of the
crystal used with the drive microprocessor. The accuracy of the crystal is 100ppm, and
so the absolute speed accuracy is 100ppm (0.01%) of the reference, when a preset
speed is used. If an analog input is used the absolute accuracy is further limited by the
absolute accuracy and non-linearity of the analog input. If analog feedback is used the
accuracy is even further limited.
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