The average business loses $13.5M per year to ineffective training (per 1,000 employees). Keep ahead of the competition and combine in-person quality with online cost and flexibility by training with Linux Academy.

Solved

Posted on 2003-11-15

How does a voltmeter work? I know an ampmeter works because as you increase current flow threw a coil, a strong magnetic pull is generated which can be used to show the flow etc. But dow does a voltmeter work? Increaseing voltate wont change how the meter moves will it?

Thank you for your time,

Arrummzen

Thank you for your time,

Arrummzen

3 Comments

On newer digital meters, a variety of techniques are used. The most common one is called dual-slope integration. There the incoming voltage is again fed into a resistor to convert the voltage to a current. Then this current is used to discharge a capacitor until the voltage gets down to zero. Then a known current is applied, and the time it takes to recharge the capacitor is a measure of the input curent.

A faster way is to apply the input voltage to a A/D converter which uses a successive-approximation technique, a version of the old "20-questions" game. First it compares the input voltage to 1/2 the maximum and decides whether the input is above or below that, then it splits the difference, choosing either 1/4 or 3/4, comparing that, then halving the interval again. After 16 such comparisons, you have the answer to within 4+ decimal digits (1 part in 65,536), after 24 comparisions you have 7+ digits(1 part in 16,000,000). That's usually more than plenty of accuracy.

As for digital volt meters, it should be added that all the forms of A/D (analog to digital) conversions, of which dual slope is just one, compare an input voltage to a reference voltage. A process is used where either the input voltage or the reference voltage is adjusted until it is close to the other. The process of adjusting is used to calculate a value for the voltage. The fastest is what is called a flash A/D. This type uses a referece that is divided into lot of voltages and each of these divisions has a comparator. The outputs of all the comparators are sorted out with high speed logic to arrive at a value. A comparator circuit is simply an amplifier that converts a tiny voltage to a big voltage that is then used to define a binary logic state.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Title | # Comments | Views | Activity |
---|---|---|---|

Probability Calculation | 2 | 62 | |

Best Graph | 2 | 56 | |

Table function | 6 | 52 | |

Math Equation | 23 | 86 |

This is a research brief on the potential colonization of humans on Mars.

Join the community of 500,000 technology professionals and ask your questions.