any errors found in step 6 are probably due sensor drift or due to slight differences in the Druck pressure standard versus the standard to calibrate the transmitter at the factory. Yokogava has included an option with their pressure transmitters that allows the user to compensate for zero errors while at the same time leaving the transmitter span untouched. This adjustment is done through a factor or paramrter called the "Zero Point Adjustment". Note,span errer can only be corrected by sending the transmitter back to the factory