Well in order to do a zero cal I would think the transmitter needs to be at zero. Only when Im at 0"wc I am also at 20ma so this function doesnt work. If I try to rezero the transmitter say for height purposes I cant because it outputs 20ma and tries to make the milliamps 4 when zero shifting. I think I can perofrm these functions backwards, meaning, at 0"wc treat that as a span adj and at -375"wc as zero and do at D/A adj for the zero ma's.
Yes the factory does weird things and this is one of them.
I will keep searching.
Thanks