We often recommend Moxa brand expansion units for additional Analog and Digital IO points. Both Modbus TCP and RS-485 options are available. For Analog modules, the unit's default configuration is for 0-10V sources. To use 4-20mA sources, it is necessary to change an internal jumper.
Begin by removing the plug-in terminals from the front and top of the unit.
Remove the screw from the back of the device. The silver panel should slide out easily.
Continue to swing the silver panel outward from the back. It will naturally rise above the front socket.
Notice the 8 jumpers on the left. These each correspond to one analog channel.
Jumping the left set of pins configures for a current source. Jumping the right set configures for a voltage source. In the picture below, the first four channels are configured to read 4-20mA and the last four channels are configured to read 0-10V.