Generate a 4-20mA output on the PXU

Traditionally Red Lion P16 could be used to send a 4-20mA signal to any engineering device via simple display with up/down pushbuttons. As P16 is now obsolete, the suggested replacement is Red Lion PXU panel meters. There are two ways to generate a controlled analogue output with PXU depending on the model.

Option 1: PXU without analogue output retransmission (i.e. PXU31AB0)
You can use PXU as a 4-20mA potentiometer. The following needs to be set in the panel:
  • Configure the PXU for Manual control mode in the hidden loop trnF: USEr
  • Configure OP1 (Control Output 1) parameter in Display Loop to be displayed and adjusted on display line 2 - The OP1 parameter displayed on line 2 is viewed in units of % output (0.0 to 100.0) only (Set Value)
  • OP1 output terminals (5 and 6) provide the analogue output
  • PXU line 1 display can be wired and configured to display the output signal level (process value0. Wire the OP1 output signal in series (for current signals) to the PXU’s input
  • Scale the input display for the desired 4-20mA After adjusting the output power, press the P key to finalize the change.

Option 2: PXU with analogue output retransmission (i.e. PXU31CB0)
If you want to display the OP1 parameter as a scaled value instead of not 0-100% you can use the PXU module with output retransmission. The retransmit can be scaled based on input or process value (PV), active setpoint (SP), or (OP). This would give you the ability to scale the 4-20 MA output to any engineering unit.

You will need to setup the analogue output to reflect either PV or set point. Signal wires are terminated to Retrans terminals 15 (-) and 16 (+) in 1/16 DIN and 18 (-) and 19 (+) for 1/8 or 1/4 DIN models.


Module 2 - Output Parameter (2-OP)
OPAC R1 or D1 Depending on the control action expected from the output 1 it could be set as direct acting or reverse acting. For that the Control Action (OPAC) in Module 2 needs to be set as R1 or D1.

CTRL
PID The control output mode of operation to be set as PID.

STPT
SP When Setpoint Control Mode is selected as SP it controls to a fixed setpoint.

ANAS
INPT or SP This setting selects the parameter that the analogue output retransmits or track. It could be set as Active setpoint value or input value.

ANLO

PV or SP value for 4 MA
The Analog Output assignment value that corresponds to 4 mA output.

ANHI
PV or SP value for 20 MA The Analog Output assignment value that corresponds to 20 mA output. An inverse acting output can be achieved by reversing the low and high scaling points.

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