Analog Position Scaling

To have any useful meaning, the Voltage or Current from an analog transducer must be scaled to measurement units. This topic describes how to manually calculate the Scaling and Offset parameters for an analog position input.

Delta Recommends using the Scale/Offset Wizard for scaling the position. If you need to do it manually, read this topic.

Manually Scaling Voltage or Current to Position Units

The RMC calculates the Actual Position every control-loop time using either of the following formulas:

Actual Position = (Voltage x Position Scale) + Position Offset

Actual Position = (Current x Position Scale) + Position Offset

Calculating the Position Scale and Offset

The Scale/Offset Wizards provide the easiest method of scaling your axis. If you want to compute your scale and offset manually, do the following:

The accuracy of this method depends on how accurately you can measure two positions of the axis.

Physically measure the axis' position at two points and record the value of the Volts register at each point. Call the smaller measured position P0, and its corresponding voltage V0 or current C0. Call the greater measured position P1, and its corresponding voltage V1 or current C1.
Calculate the Position Scale with the following equation:

Position Scale = (P0-P1)/(V0-V1)
Position Scale = (P0-P1)/(C0-C1)
Calculate the Position Offset with the following equation:

Position Offset = P0 - Position Scale x V0
Position Offset = P0 - Position Scale x C0