Prokit's Industries MT-4018 - Manual (Page 11)

can press button Up or Down to choose the proper
range.
When LCD appears UNDER symbol, it indicates
that the range is high, you need to press button
Down
to set lower range until no UNDER symbol.
Press button Down and button ON/OFF at the
same time, automatic shutdown will not occur.
■. Calibrating Sound level Meter
When Sound Level Meter is used for a long time,
the accuracy may reduce, you need to check and
calibrate it, normally a time for each year.
Calibration needs a standard sound source, please
contact with us about the method.
■. Maintenance
1. CLEANING INSTRUCTIONS
The meter may be wiped down with a wet sponge or
cloth using a mild water based detergent or
anti-bacterial soap and rinsed under a gentle stream