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What can cause the 4-20mA signal to latch at 20mA on the ATV61 or Eflex drives?

Published date: 15 October 2019

Issue:
What can cause the 4-20mA signal to lock in at 20mA on the ATV61 or Eflex drives?

Product Line:
Altivar ATV61 Eflex

Environment:
All

Cause:
Noise issues

Resolution:
A voltage surge or spike on the mA input exceeding 7.9 V on this input will cause the analog input to jump to 20 mA and to stay there until power is cycled.
If the voltage surge/spike can't be eliminated by proper cable routing and shielding, or through the use of an isolator you can install a 6.8 V zener diode (available at most electronic stores) to prevent the excess voltage from reaching the AI2 input.
Put the cathode end (marked with a line) on the AI2 input, and the other end on the COM terminal.   

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