AI835 ch8 as cold junction
I am working on one project, the susyem is AC800M PM856 + AI835 for industrial frunace project.
If I use all 8 channels of AI835 as TC input, the error is about 5 degree, same for 3 boards, we used a gauge meter to simulate TC signals.
So I used Ch 8 as cold injunction, connected to one 4-wire PT100 RTD, connected as shown in the manual. but It doesn't work. Ch8 shown a triangle error, I dn't know what is wrong?
in the property tab, I set channel 1 to7 measured via channel 8, set ch 8 Pt100, -40~100. also has one variable connected to ch8.
zhanhg/zhihong, former ABB service engineer.
the cjt setting is measured via ch8 for ch8 also ? it should not be fixed junction temp.
Then you have not mentioned which TU you are using but check connection should be as mention below w.r.t TU830
Also take a note where RTD should be placed ?
I recommend to test first using FJT(fixed junction temperature) if the TC reference junction temp. is not varying and remains stable or almost fixed. For this you need to select second option in marked circle above. as well as enter FJT value in 'C in module parameter.
Also check if you are getting row values for all the channels and using some scale block or you are getting direct physical value ? if there is any scaling blocks check input/output range to convert row value to physical value ! you get row values in memory map doc.
Hope that helps.