Please give a detailed answer
2007-05-26 18:14:29 · 5 answers · asked by Anonymous in Science & Mathematics ➔ Engineering
For minimum disturbance to the circuit under test, a voltmeter should look to the external circuitry as close to an open circuit (infinite impedance) as possible, while the ammeter should look as much as possible like a short circuit (zero impedance).
In operation, the voltmeter shunts a small amount of current around the circuit it is measuring. This limits the the maximum impedance of the circuit that the meter can connect to without unduly loading the circuit under test and changing the circuit's characteristics simply by being connected to the circuit.
Similarly, an ammeter with a too-high resistance will cause a voltage drop across it that wasn't there before the meter was inserted. The impedance of the meter limits how low the circuit's impedance (and voltage) can be without interfering with the circuit's operation.
2007-05-26 18:37:26 · answer #1 · answered by devilsadvocate1728 6 · 0⤊ 0⤋
in order to measure the current an ammeter should be connected serially to the part it will measure the current flaws through it ( not to make any change of its value) in other words current flaws through the ammeter and as we know the Resistance of this instrument should be as small as possible. it is assumed to be zero.
as for the voltmeter which needs to be connected on parallel to the circuit to measure its voltage (to get the same voltage ) and in order not to make any change to the circuit resistance and to the voltage value so its resistance should be as large as possible, in other words infinity
2007-05-26 19:15:53 · answer #2 · answered by fofo v 1 · 0⤊ 0⤋
as for details, the voltmeter is put in parallel to a circuit to measure voltage. if it has less than infinite resistance, then it changes the resistance of the circuit.
similar logic for the ammeter, which is placed in series in teh circuit.
2007-05-26 18:32:38 · answer #3 · answered by Piglet O 6 · 0⤊ 0⤋
Like the rest of the equipment; you got to know that even meters are made of actual materials: copper wires, shunt resistors, solder joints, so on. Each type of measuring device is know to the tech's using them most that they have limitations. For example I prefer measuring with an o-scope better than a meter (coil movement) because of a higher input impedance and less effected by frequencies.
2016-05-18 22:52:23 · answer #4 · answered by ? 3 · 0⤊ 0⤋
ideal, values zero for ammeter
infinity for the voltmeter
2007-05-26 18:20:48 · answer #5 · answered by lord 3 · 0⤊ 0⤋