zero calibration in AC800M
how to calibrate zero in any analog input signal if it is showing some offset value.
Like in MOD300 we use to set offset counts as zero.
is there any option to to do the same in ac800m except possible two or three predefined options in settings tab of Signal (harware allocation).
Voted best answer
No, there is no equivalent option in the AC800M.
If your instrument doesnt read 4mA when your process is at "zero", then it either isnt calibrated properly or it isnt installed properly. Fix the instrument.
I've seen this option used, and more commonly abused, on several MOD300 sites. In many cases I've seen signals where the counts are adjusted to fix a "problem" and some time later somebody else has gone back and "adjusted" the measurement range to "fix" a transmitter that wasnt reading properly. the result being that both the A/D counts and signal ranges cancel each other out.
The option to adjust the "counts" on an A/D transmitter probably sounded like a great idea when the MOD was first developed. It was fairly common at one time to be able to adjust the "zero" of an analog signal slightly.The principle was that A/D converters were not always completely accurate and you could tweak the 4mA slightly. Unfortunately the MOD300 took this idea to extremes and you could basically adjust the A/D converter counts to pretty much any values you wanted. Not surprisingly, this gets widely abused.