What happens when the resistance of a voltmeter is less than that of a resistor connected across its terminals

Question

Also, why is a "high quality" meter rated with a higher value of ohms/volt? Any help is much appreciated!

They are connected in series. Also, why is a "high quality" meter rated with a higher value of ohms/volt? Any help is much appreciated!

Answer 1

Ideally, a voltmeter measures voltage without influencing the circuit you are measuring. A real-life voltmeter isn't ideal. It draws some current during the process of measurement. The more current drawn by the meter, the more it interferes with the circuit.

A 1000-ohm resistor connected to a 1-milliamp current source will have a voltage of 1 volt across it. If you connect a meter rated at 1000 ohms per volt, your 1-milliamp current will be divided equally between the resistor and the meter. Your reading will be 1/2 volt instead of 1 volt. With a 10,000 ohms per volt meter, your meter will draw only 10% of the current through the resistor, so your reading will be off by only about 10%.

Ideal for accurate voltage measurement is a bridge circuit with a reference source. The galvanometer need not be calibrated. It draws a tiny current, and its current is zero when the reference voltage exactly equals the measured voltage.

Answer 2

First off, if a voltmeter is connected across the terminals of a resistor, then its internal resistance and the resistor are connected in parallel. This is why a voltmeter should have a very high resistance, on the order of tens or hundreds of megaohms. If the resistance is less in the voltmeter, then you are effectively changing the circuit the resistor is in, causing a false reading. More current would pass through the circuit including the voltmeter with the meter connected. The voltage reading on the meter would be higher than what the circuit would really have across that resistor if the meter weren't connected.

The quality of a meter has nothing to do with its range of operation. The quality of a meter is determined by its ability to display with high exactness the value it is measuring with the least interference to the circuit it is measuring.
It just so happens that in order to make a meter that reads higher voltages, and I suppose higher resistance although thats not usually a problem, more care needs to be taken in the design of the meter as far as components that are capable of measuring and supporting higher voltages/currents. This makes for a more expensive meter.

Answer 3

that all depends on if they are connected in parallel or in series