In a AB PLC-5, every time the analog value (level of a tank) goes over 20 mA, it resets to zero. It seems that over 4095 (20mA) the quantity goes back to zero.

Does anybody have any experience how to fix that?

 

I have seen many transmitters that fail back to zero if the URV is exceeded.For instance if the tank you are meauring is 25' tall but your transmitter is spanned to only 18'and your upper range value is is less than 25', then if the level gets up to 25' the transmitter fails back to zero even though the tank is really full. Try setting the failover to full scale (100%) instead of zero.