I would like to confirm following items for LD4A05P0 product:

  1. If the input signal is 4-20mA analog, I will need to follow the following wiring diagram and need extra power supply.

I am just confused about the word EXCITATION and CURRENT.

If I read correctly, that refers to the case where the LD4xxxx is supplying voltage to some sensor that allows between 4 and 20 mA to pass in response to the quantity being measured. The EXC pin in that event would appear to be the one that’s supplying voltage/sourcing current, and the CURRENT pin the one that’s measuring how much current the sensor is allowing to pass.

Hi Rick,
So if the transmitter is loop powered then the I would connect pin 4 and pin 3?

The transmitter I plan to use is not loop powered, so I think I should use pin 3 and pin 2?

A 4~20mA transmitter that isn’t powered by the loop does not necessarily power the loop. Many will simply provide what amounts to a variable resistance to modulate current flow through a loop that’s being driven by an external voltage source. Use 3+4 in such a case. If the device transmitting data also provides the voltage source necessary to cause current flow in the loop, use 2+3.

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Kindly see below diagram for function of Pin 4, EXC

It is a source for 24VDC supply voltage for the sensor.

It would be used with sensors that can accept a 24VDC supply voltage with a current output signal.

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