I just had to replace a SLC 1746-NIO4I analog card that was doing something I have never seen before.
Only 1 channel was used, and I tried the other and it acted the same. Set to 4-20mA input. It is on a Banner LTF laser distance sensor for a hoist position, and I replaced that first, then checked for blockage or stray reflection on the reflector.
The reading of the signal from 4 to 18mA was perfect, and from 18.7 to 20mA was perfect. However, from 18.1 to 18.6mA the reading on the PLC dropped from 14,800 to 9,000 - stayed about 9,00 for 8 inches of movement, then jumped to 15,600 and climbed steadily. This happened moving both directions, and was very repeatable on both channels.
Has anyone else ever had an analog input develop a "deadspot"?
Only 1 channel was used, and I tried the other and it acted the same. Set to 4-20mA input. It is on a Banner LTF laser distance sensor for a hoist position, and I replaced that first, then checked for blockage or stray reflection on the reflector.
The reading of the signal from 4 to 18mA was perfect, and from 18.7 to 20mA was perfect. However, from 18.1 to 18.6mA the reading on the PLC dropped from 14,800 to 9,000 - stayed about 9,00 for 8 inches of movement, then jumped to 15,600 and climbed steadily. This happened moving both directions, and was very repeatable on both channels.
Has anyone else ever had an analog input develop a "deadspot"?