# How to connect 4 wire RTD to PLC?

**URL:** <https://forumautomation.com/t/how-to-connect-4-wire-rtd-to-plc/1545>\
**Category:** PLC (Programmable Logic Controllers)\
**Created:** [December 3, 2016, 3:28pm UTC](https://forumautomation.com/t/how-to-connect-4-wire-rtd-to-plc/1545 "2016-12-03T15:28:38Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![automate](https://forumautomation.com/letter_avatar_proxy/v4/letter/a/51bf81/32.png) [@automate](https://forumautomation.com/u/automate)\
**Post date:** [December 3, 2016, 3:28pm UTC](https://forumautomation.com/t/how-to-connect-4-wire-rtd-to-plc/1545/1 "2016-12-03T15:28:38Z")

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How we can connect 4 wire RTD to PLC cards?

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**Author:** ![denizen](https://forumautomation.com/letter_avatar_proxy/v4/letter/d/848f3c/32.png) [@denizen](https://forumautomation.com/u/denizen)\
**Post date:** [December 17, 2016, 2:56pm UTC](https://forumautomation.com/t/how-to-connect-4-wire-rtd-to-plc/1545/2 "2016-12-17T14:56:52Z")

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Two Options are there to connect 4 wire RTD to PLC.

First option is to use RTD-mA converter.

RTD-mA converter (Transmitter) is usually a better option that wiring RTD directly to the PLC card.

There are advantage of using this method.

1.Reduce the cost by not using a different type of PLC input card. 2.Some PLC card do not allow individual calibration of RTD channels.

2nd method of connecting 4 wire RTD to PLC input.

It is possible to connect a 4 wire RTD to a 3 wire input by just not connecting the sense wire. You can also connect to 2 wire input by not connecting either sense wires.

For every sense wire you do not connect the accuracy of the temperature measurement in your controller is reduced.