cardosocea
Member
Hi guys,
I just came out of the plant where I had two temperature probes (4-20mA) installed today in two exactly same hydraulic power units.
Both these sensors go to two channels in a Flex IO module.
We wired the first one, compared the reading to the sensor and program and everything was fine.
We then wired the second sensor, connected to the IO and was showing 4.1 mA... this was strange, so we plugged in the configuration unit to the probe and it was stating 6.1 mA output.
I confirmed with a meter and it showed 6.1mA output as well.
Thinking it was the channel, I swapped the two around and the behaviour moved with the probe, so it isn't the card.
I then connected a loop calibrator and checked the sensor reading without the PLC and it was the same 6.1mA.
I connected the sensor to the PLC and put the loop calibrator in measure mode in series in the loop and it showed 6.1mA while the PLC still reported 4.1mA.
I injected current in the card and it was a reasonable reading through the range (not 4.1mA).
I checked the PLC card configuration and it was showing that input configured with 4-20mA too...
I'm really at a loss as to what can be going wrong here. Any takers?
I just came out of the plant where I had two temperature probes (4-20mA) installed today in two exactly same hydraulic power units.
Both these sensors go to two channels in a Flex IO module.
We wired the first one, compared the reading to the sensor and program and everything was fine.
We then wired the second sensor, connected to the IO and was showing 4.1 mA... this was strange, so we plugged in the configuration unit to the probe and it was stating 6.1 mA output.
I confirmed with a meter and it showed 6.1mA output as well.
Thinking it was the channel, I swapped the two around and the behaviour moved with the probe, so it isn't the card.
I then connected a loop calibrator and checked the sensor reading without the PLC and it was the same 6.1mA.
I connected the sensor to the PLC and put the loop calibrator in measure mode in series in the loop and it showed 6.1mA while the PLC still reported 4.1mA.
I injected current in the card and it was a reasonable reading through the range (not 4.1mA).
I checked the PLC card configuration and it was showing that input configured with 4-20mA too...
I'm really at a loss as to what can be going wrong here. Any takers?