Elenco Electronics ST-3030 Operator's Instruction Manual page 15

Back Light
On any range, press the "D.HOLD" button for over two seconds to
light the backlight. Press it again for more than two seconds to wink
the light.
Relative Measurement
Press the "REL " button. You can measure the relative value and
the " " symbol will appear on the display. The auto range mode will
be changed to manual mode. Press it again to exit the relative
measurement and the " " symbol will disappear, but you cannot
return to the auto range mode. This function can be used to zero
the reading on the DCA range. This function is non-effective on the
Hz/DUTY measurement.
Auto/Manual Range
The auto range mode is a convenient function, but it might be faster
to manually set the range when you measure values that you know
to be within a certain range.
To select the manual range, press the "RANGE" button repeatedly
until the display shows the desired range. The range steps upward
as you press the "RANGE" button.
The meter will go back to auto range mode when you press the
"RANGE" button for more than two seconds. It cannot select the
manual range mode on Hz/DUTY, capacitance, or temperature
ranges.
Caution: While using the manual range mode, if "OL" appears on
the display, immediately set the clamp meter to a higher range.
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