Ammeters,Voltmeters,Ohmmeters

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This page will describe certain tools that are used in measuring various values inside of a circuit. Using these tools can help you calculate current, voltage, power and resistance across various circuits.

Ammeters

What is an Ammeter

An Ammeter is a measuring device used to measure the electric current in a circuit. It can be used in both series and parallel circuits. This is plausible through the very negligible resistance that the Ammeter introduces to the circuit. It allows us to measure the current running through a circuit element very closely. An Ammeter measures current in Amperes(A) named after Andre Marie Ampere.

Connecting Ammeters

To properly use Ammeters, they must be inserted into a circuit in series with the element that you want to measure. You bring the current into the + socket and out of the - socket. If a positive number is read then the conventional current is flowing into the + socket. Therefore, a negative number is read when conventional current flows into the - socket.

Ammeter in Parallel?

One rule of Ammeters is to have a low resistance so it doesn't alter the current through the circuit and the element that is being measured. So,what happens if you connect the Ammeter in parallel?

This would create an extremely low resistance path("short circuit"). All of the current would then pass through the Ammeter and the reading would be a measurement of the maximum current that the batteries(voltage source) can provide.

Voltmeters

What is a Voltmeter

A voltmeter is a measuring device used to measure the potential difference across two points in an electrical circuit. A Voltmeter is created by adding a series resistor (with resistance R) to an Ammeter and attaching this across an element. There is a measured current of I and the potential difference across the resistor is Va – Vb = RI. The ammeter is then relabeled and now measures Volts.

Connecting Voltmeters

To measure the potential difference across two points, we need to attach the voltmeter in parallel to the two points. If the potential is higher at the + socket, the voltmeter indicates a positive potential difference. If the potential is higher at the – socket, the voltmeter indicates a negative potential difference.

Wrong Connections

Since the Voltmeter has a very large resistance, placing it in series throughout the circuit will cause a very large disturbance throughout the circuit. It would change the current running through the circuit drastically.However if the Voltmeter had low resistance and was placed in parallel, this causes a short circuit to occur.

Ohmmeters

Examples

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Simple

Middling

Difficult

Connectedness

How is it connected to your major?

I am a Computer Engineering(CompE)(both my major and something that interests me) student here at Georgia Institute of Technology. This is a topic that is extremely important to the world of ECE. We use these measuring devices in numerous real-life applications and building of circuits. They are a vital part to both teaching and understanding how a certain circuit performs.

Is there an interesting industrial application?

Nowadays, most of these calculations are done computationally so there is no need for these physical measuring devices. However, some places still use these measuring devices in day to day life.

History

Put this idea in historical context. Give the reader the Who, What, When, Where, and Why.