I have an MSA X5000 gas detector that is considered to be a 3-wire transmitter. I know that I can use the 3-wire fused injected terminal block to make a clean and certain connection to the 4020mA AI CHARM. However, this would be a one off setup as the other IO in the system is using all standard terminal blocks. Does anyone have experience wiring a 3-wire transmitter to a standard terminal block and using an external 24VDC power supply? This particular transmitter will be on an SIS CHARM. I will have one 3-wire flowmeter on a DCS CHARM with the same question.
The sketch below looks like it would work. But I don't know if the ground inside the CHARM will drain loop current so that none returns to the external 24VDC you're showing. Or does it get sort of split between both paths? The 24VDC I'm showing is an external supply.
Hello Greg,
Looking at the actual 3-Wire AI Terminal Block wiring, terminals 3 and 4 are coming straight from the Injected Power, the only terminal being used is Terminal 2, receiving S (signal) from the transmitter, there's no need for you to go thru Terminal 4 as you're pointing out in your scheme.
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Andre Dicaire
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