Hi robert swift，
Thank you for writing in.
000.3 is the base number of the meter,which cannot change it.
And the button on the back of the meter is used for adjusting voltage compensation.
When the driving load in the circuit is large.There will be voltage drop when wiring.At this time, the voltage
value displayed on the meter is not the exact output voltage of power supply.The voltage compensation function can
compensate voltage consumption of the wire so that can get a more accurate measured value of the output voltage of
the power supply.
When using the voltage compensation function, you need to connect a 5-digit multimeter to the output of the system
power supply.In the case without power, press and hold the button and then power the meter. At this time, the
ammeter will display [**].** is the stored voltage compensation level (the default value of ** is 00,i.e. no
voltage compensation).Then release the button, it will display–**.
When display–**, you can set the voltage compensation level. Connecting the large load to the circuit(it is
recommended that the current of the load is more than 2A, the voltage compensation value will be more accurate). Short pressing the button can increase 1 level. The max. level is 99. Adjust the value of the level until the voltage displayed on the meter is the same as the multimeter. Long press for more than 2 seconds to store the value. After that, the meter will measure the voltage with voltage compensation. If you want to turn off the function, you can set the voltage compensation to 00 level.
This meter is well-calibrated before shipping to Amazon warehouse, which cannot be calibrated by yourself.
Hope this can help you.
Best regards
robert swift
