adccommunitymod (AutomationDirect) asked a question.
Created Date: May 13,2010
Created By: bartb102
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I am having a noise issue with two F4-08RTD modules on a 5KV generator. Occasionally all channels will become noisy with fairly wide indicated temperatures. One module is on the windings, the other is on bearings, oils, and air. The temperatures will stray for about 5 to 10 minutes then settle back to normal behavior. As ambient air temperatures increase it gets worse- no problem all winter, now it is starting up again. I 've had to put time delays on most of the alarms to avoid unwanted shut downs. The identical systems are installed on three other generators in the same plant and they do not display this behavior. Graph is attached. I have replaced the bearing RTD module as that has the wildest behavior. The PLC has also been replaced. I am assuming it is probably noise on the ground system, but then it should affect all four units, not just this one.
Created Date: May 13,2010
Created by: doug6949
I had similar problems with that module about a year ago - never did get the noise out of it.
Another member of this forum said he had the same problem. He attributed it to lack of noise rejection with the Host Engineering RTD card itself.
After a few more more months of fighting it I finally pulled the card and used an external module.
YMMV, of course. This isn't my area of expertise.
Doug
Created Date: May 14,2010
Created by: Forrest
I also have the same problem. I am now using F2-04RTD mdoule and PT100. I only use one of the channel to detect temperature change inside a water tank. In my program, I created a PID loop to control temp. I found that the temperature reading is fluctuating.
I followed the isntruction in manual to reduce the noise but it didn't work. What can I do now?
Created Date: May 17,2010
Created by: bartb102
If you haven't done it already, putting a 100 ohm (or what ever your RTDs are) resistor on the unused inputs will help. Filtering the values also helps somewhat, if your process can take the time delay.
At one plant we had to install separate RTD-4-20MA converters located near the RTDs and change to a standard 4-20ma input card. Of course this was at a plant with OLD 12KV @ 40 cycle generators.
My concern is that 99% of the time the noise I see is bearable, say +/-4 degrees C, but that it increases substantially (+/-30 degrees C) for short periods. Most noise will exist continuously, but mine is sporatic. I have been unable to attribute it to any other event/cause.
Created Date: May 17,2010
Created by: Forrest
Thanks bartb102
I haven't done it so I could try to add 100 ohm resistors to un-used inputs.
Created Date: May 13,2010
Created by: bartb102
I am having a noise issue with two F4-08RTD modules on a 5KV generator. Occasionally all channels will become noisy with fairly wide indicated temperatures. One module is on the windings, the other is on bearings, oils, and air. The temperatures will stray for about 5 to 10 minutes then settle back to normal behavior. As ambient air temperatures increase it gets worse- no problem all winter, now it is starting up again.
I 've had to put time delays on most of the alarms to avoid unwanted shut downs. The identical systems are installed on three other generators in the same plant and they do not display this behavior. Graph is attached. I have replaced the bearing RTD module as that has the wildest behavior. The PLC has also been replaced.
I am assuming it is probably noise on the ground system, but then it should affect all four units, not just this one.