I have a Beckhoff PLC with many AI modules. Most devices are loop powered using the same +24 VDC power as the Beckhoff Bus Coupler and all is working fine.
I have some panel mounted controllers powered by 120 VAC that spit out some outputs that go to my AI modules and they bounce like crazy! I have the controller send a simulation signal of 12 mA and my Fluke Voltmeter reads 12.0 solid. On the AI module it bounces quickly from 11.5 to 12.9 mA. This happens on 2 types of controllers from different manufacturers so I can't blame the controllers.
All I can think of is that these are 110 VAC devices that do not share the 24 VDC power as the Beckhoff modules. The controllers must create its own 24 VDC power to spit out powered 4-20 mA outputs. All other AI devices work perfectly.
Everything is grounded. All devices, including these controllers share a ground.
This is in a plant with VFDs nearby and it is noisy.
What can be causing this???
I have some panel mounted controllers powered by 120 VAC that spit out some outputs that go to my AI modules and they bounce like crazy! I have the controller send a simulation signal of 12 mA and my Fluke Voltmeter reads 12.0 solid. On the AI module it bounces quickly from 11.5 to 12.9 mA. This happens on 2 types of controllers from different manufacturers so I can't blame the controllers.
All I can think of is that these are 110 VAC devices that do not share the 24 VDC power as the Beckhoff modules. The controllers must create its own 24 VDC power to spit out powered 4-20 mA outputs. All other AI devices work perfectly.
Everything is grounded. All devices, including these controllers share a ground.
This is in a plant with VFDs nearby and it is noisy.
What can be causing this???
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