Voltmeter LCD.Digital +/- 0-200V.DC Auto power off. 

Measures from 0.0 to 199.9 volts DC. (100mV resolution)

Powered by a standard 9V battery, easy to change when required.
A "LO-BATT" alarm displays well before the battery must be replaced and accuracy is not affected.

Power turns off automatically after 20 minutes to protect against forgetful users. One touch of the only button restores the display.

If the 20 volt DC rating is exceeded, a red LED illuminates as a reminder but there is no chance of damage.

There are no knobs or switches or fuses to replace. A perfect voltmeter for the classroom and not much more expensive than a fragile analogue meter.