Features and Functions        3
Agilent U1251A/U1252A User’s and Service Guide 63
NULL (Relative)
The NULL function subtracts a stored value from the present 
measurement and displays the difference between the two.
1 Press   to store the displayed reading as the 
reference value to be subtracted from subsequent 
measurements and to set the display to zero. NULL is 
displayed. 
2 Press   to see the stored reference value. NULL 
flashes for 3 seconds before the display returns to zero.
3 To exit this mode, press   while NULL is flashing on 
the display. 
Null can be set for both auto and manual range settings, but not in the 
event of an overload.
• When taking a resistance measurement and the meter reads a 
non-zero value due to the presence of test leads, use the Null function 
to adjust the display to zero.
• When taking a DC voltage measurement, the thermal effect will 
influence the accuracy. Short the test leads and press NULL once the 
displayed value is stable in order to zero out the display.