Martel Electronics 235 - Manual (Page 35)

If a pressure of 1478.7 PSI (98.85% of scale) is applied, the transmitter
would be expected to output 98.58% of range or 19.773mA. If the
transmitter were outputting only 19.757 (which is a -.1% error), the
display would indicate:
It is then a simple matter to adjust the transmitter span to achieve a 0%
error reading.
The calibration technique is to adjust zero for zero % error and adjust
span for zero % error. Repeat as required.
To configure the % ERR display, first select the desired input and output
engineering units (V, mV, mA, or Pressure). Then select the % err
option from the Setup menu, and the 130 will display the prompt:
Then both the 230 and 235 will prompt:
Exit the Setup menu.
The 230 will display the input in % ERR and the output in % Scale on exit
from the setup menu.
The 235 will now display in the previously selected Engineering Units.
Operation
230/235 30
% error % scale
-0.10% +98.58%
% error
Disable Enable
Enter input Zero
EngUnits ???????
Enter input F.S.
EngUnits ???????
Enter output Zero
EngUnits ???????
Enter output F.S.
EngUnits ???????