Should a voltmeter have a low or high resistance?

A voltmeter is a device used to measure the electrical potential difference between two points of an electrical circuit. Analog voltmeters shift the pointer around a range following the circuit's voltage; digital voltmeters show the voltage using an analogue-to-digital converter. A voltmeter measures the voltage difference between the two points (say, on opposite sides of a resistor), but it does not adjust the amount of current passing between these two points through the device. Therefore has very high resistance so that it does not draw current. The lower the resistance the voltmeter puts across the load, the more wrong the reading will be on the voltmeter. The best voltmeter will have such a high resistance that it will not significantly change the current in the circuit. Good, modern voltmeters have several megohm input resistance. Ideally, an ammeter should have zero resistance and an infinite voltmeter resistance to give correct readings.