Switching the pressure input on a position-pressure axis

Delta has run across some position-pressure or position-force applications where the customer wants to change the pressure or force feedback to a different transducer during the machine operation.

Here are two different methods of doing it. Method 1 is the easiest, but requires discrete inputs. Method 2 requires a fair mount of programming and restarting the controller.

Method 1: External Switching
Use an external relay to switch the different pressure signals. The discrete outputs on the D8 expansion module or DI/O module can be used to switch the signals, since they are actually solid-state relays. Delta has actually tried this out, and it works great. This method would be easier than the first method. One discrete output is required for each signal. If using the D8 or DI/O module, when wiring it up, the common side of the discrete outputs must go to the analog input. This means that no other outputs on the same D8 or DI/O module can be used for other purposes.
The switching is done only on the positive signal coming from the transducer or load cell. For example:
The signal common wires must all be run from the transducer and load cells to the analog input (-) input on the RMC and to the Analog Cmn on the RMC. Those signals are not switched.

Method 2: Redefine the Axes
It is possible to redefine the axes programmatically. It is somewhat involved, and requires a restart of the controller (which can also be done programmatically). This is described in the RMCTools help. In the help, on the Index tab, type “Axis Definition Registers”, and open that topic. With this method, all the pertinent axis parameters need to be updated after the restart, because changing the axis definitions sets them to default values.

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