Using Analog Channels as Position Inputs

Analog channels may be configured to be used as one of two position input types:

Position Control - The input is used with the corresponding drive output (analog modules without drive outputs cannot be used for position control) for closed loop control. See Controlling Solely Position, Pressure, or Force for details.
Position Reference - The input is used without the drive output. The incoming counts are scaled to position units, but otherwise the axis does no control. This is most often used for joysticks, in which case another axis will be slaved to the movements of the joystick on a position reference axis. See Using Position and Velocity Joysticks or Using an External Target Generator for details.

For both position inputs, all fields are used as described in the position status, command, and parameter field topics. One field worthy of note is the Transducer Counts field. See the section What to Expect in the Transducer Counts Field below for details.

When using Position Reference, the only parameters that are used are Configuration word, Scale, Offset, Extend Limit, and Retract Limit. All others are ignored.

Use the following steps to configure an analog position input:

Step 1: Assign Analog Channel(s) to be Position Input(s)

Because only channels 0 and 2 have drive outputs associated with them on the analog modules with drive outputs, it is only these two channels that can be configured as Position Control; any channel may be configured as Position Reference. Use the following steps:

On the Tools menu, click Module Configuration.
In the Slots list, click an analog module.
Click Slot options.
In the Analog Channel Assignment dialog box, click the tab of the channel pair (0-1 or 2-3) you wish to reassign.
Click the option button of a channel assignment that designates one or more channels as Position control and/or Position Reference. The assignment selected depends on how you intend to use the all channels.
Click Update RMC.
The Update Module Configuration dialog box will be displayed to indicate the progress. If the RMC could not be reset automatically, you may be prompted to reset it manually.
In the RMC Configuration dialog box, click Close.

Step 2: Configure the Analog Transducer Type for the Position Input

Refer to Configuring the Analog Transducer Type for details on selecting between a voltage or current input type.

Step 3: Set the Scale, Offset, Extend Limit, and Retract Limit Parameters for the Position Input

Refer to the individual field sections for details on setting each parameter.

What to Expect in the Transducer Counts Field

The Counts reading will vary depending on the transducer type selected. Refer to that topic for a description of the mapping of input voltage or current to counts.

Analog Input Ranges

See the COUNTS topic for detailed information on the maximum and minimum limits of the various analog input ranges.