Martel Electronics 320 - Manual (Page 30)

To place the Model 320 into the calibrate mode, press
6 (user cal) while in set up mode, screen number 2.
The unit will prompt for the access code to be entered.
Enter the calibration access code from the individual
calibration data sheet that is supplied with the unit. If
the correct access code is entered, the Model 320 will
enter the calibration mode as shown below.
The following keys are active during calibration
mode.
28
enter access code
?????
volts user cal
+ 10.000 volt in