It is on a IO-PT4 I tried several channels with same results.
Checked it is set for PT100 with 385 and also tried .392 as well same results.
I am checking raw value as written to a Memory Integer by the IO-PT4
Last night I wrote a new program to test it that only display the current temp value on HMI, nothing else in the program and ran it. I then manually turned on the outputs to the heater and I had exact same results.
I then took one of the other RTD that worked from its tank and placed in in the liquid that I was heating and it worked. So I pulled the troubled probe and put this in its place but left the wiring alone. I didn't change wiring to see if it would still read ok like it did when I held it in the water.
It did not work. it did the same thing, holding the one I took out in the liquid now worked. So it appears to only happen when I have it mounted in the tank.
it is mounted using Camlock fittings so I can quick release it I also tried isolating its ground in case it was ground issue. I think it might be related to noise somehow generating from the heating element. That element is just above and perpendicular to the probe see attached photos. Perhaps the heating element is generating too much EMI? The placement of the Probe and its orientation to the element causing issues? or could it be mounting it in the stainless steel tank which is grounded via the element mount. causing some interference with the signal? since it reads fine if I hold the probe above with its probe in the water but above the element and not to the side
Complex little bugger of q question I am sure. Any help would b appreciated
Thanks