F8-THM-k Thermocouple Module

[Alan Wain 0]

Does anyone have sample code showing how to add input filtering on Thermocouple inputs. I have followed all the required hardware installation requirements and still get irratic readings. I see fluctuations of 20-25F even with the inputs shorted which should show a stable ambient temperature. The T/C module is in slot 1 of a 10 slot base with a 350 CPU.

[BobLfoot 302]

I'm no guru for PLC Direct, but if shorted terminals fluctuate 20 F then you've got someting really flaky in your setup. Just mho. As far as filtering the simplest filter on an analog input is to add a percentage of the new and 1 - percentage of the old to get the filtered reading. Math looks like follows: Filtered Reading = (0.25 * New Reading) + (0.75 * Previous Filtered Reading) You apply this logic after each new reading. The larger the percentage of new reading the less filtering.

[TimWilborne 108]

Are you shorting the inputs at the terminals or at the end of the thermocouple wires? Do you have the cold junction input hooked up? Is is reading stable?