In order to measure a device's voltage, a voltmeter is connected in parallel to a device. This setup is important as objects in parallel usually tend to experience the same potential difference. It is connected in parallel with the circuit mainly because the same voltage drop occurs across it.

A voltmeter also has high internal resistance. This is done mainly because it is used in measuring the potential difference between the two points of the circuit. As such the current of the measuring device remains the same. In other words, the high resistance of the voltmeter will impede the flow of current through it. This allows the device to take correct readings of the voltage.

Dimensions

The above image gives us a bit more information on the 100A Digital Amp meter with backlight, as well as the dimensions of the display on the unit.

100A Digital Amp meter with backlight Specification