What do ammeter measure

Analog meters have needles that swivel to point at numbers on a scale, as opposed to digital meters, which have numerical readouts. The heart of most analog meters is a device called a galvanometer, denoted by G. Current flow through a galvanometer, I G , produces a proportional movement, or deflection, of the needle. The two crucial characteristics of any galvanometer are its resistance and its current sensitivity.

By connecting resistors to this galvanometer in different ways, you can use it as either a voltmeter or ammeter to measure a broad range of voltages or currents.

A galvanometer can function as a voltmeter when it is connected in series with a large resistance R. The value of R is determined by the maximum voltage that will be measured.

The total resistance must be:. R is so large that the galvanometer resistance, r, is nearly negligible. This voltmeter would not be useful for voltages less than about half a volt, because the meter deflection would be too small to read accurately. For other voltage ranges, other resistances are placed in series with the galvanometer. Many meters allow a choice of scales, which involves switching an appropriate resistance into series with the galvanometer.

The same galvanometer can also function as an ammeter when it is placed in parallel with a small resistance R , often called the shunt resistance. Since the shunt resistance is small, most of the current passes through it, allowing an ammeter to measure currents much greater than those that would produce a full-scale deflection of the galvanometer. Suppose, for example, we need an ammeter that gives a full-scale deflection for 1. Since R and r are in parallel, the voltage across them is the same.

Null measurements balance voltages so there is no current flowing through the measuring devices that would interfere with the measurement. Standard measurements of voltage and current alter circuits, introducing numerical uncertainties. Voltmeters draw some extra current, whereas ammeters reduce current flow. Null measurements balance voltages, so there is no current flowing through the measuring device and the circuit is unaltered.

Null measurements are generally more accurate but more complex than standard voltmeters and ammeters. Their precision is still limited. When measuring the EMF of a battery and connecting the battery directly to a standard voltmeter, as shown in, the actual quantity measured is the terminal voltage V.

Voltmeter Connected to Battery : An analog voltmeter attached to a battery draws a small but nonzero current and measures a terminal voltage that differs from the EMF of the battery. Note that the script capital E symbolizes electromotive force, or EMF. Since the internal resistance of the battery is not known precisely, it is not possible to calculate the EMF precisely. Resistance in Series Explained. Power Factor Explained.

What is the Electricity Demand In Canada? Total Harmonic Distortion Explained. Windmills For Electricity Explained. Substation Maintenance Training. High Voltage Training Online. UPS System Training. Dec, Building Automation Training. High Voltage Safety Training. VFD Drive Training. Power Quality Analysis Training. The ammeter is designed using a moving coil with a pointer moved by a galvanometer. You should connect the ammeter in series with the circuit element. An ammeter is designed to have a very low resistance inside it.

We will add a 0. Even if the ammeter has 0. It is a waste of course. Now you understand why the ammeter is designed to have very small resistance as close as to zero. To not affect the current value, the ammeter uses a small resistor connected in parallel with the galvanometer.

The purpose of this design is to make all the current flows through the resistor. Just as you learned in basic electronics, more current will flow through a lesser resistance branch. The next problem: is ammeter a digital measuring tool? The answer is NO. An ammeter is an analog tool. The ammeter is not even mechanical.

The digital ammeter you use must have a digital display 7-segment display , but it is because of the converter. The digital multimeter uses an ADC Analog-to-Digital Converter provided by a microcontroller that does all the calculation and the display through a resistor. Ideally, an ammeter has zero resistance so the ammeter will not change any value in the circuit.

But as we realize already, the ideal condition is only occurred in mathematical analysis, not in practical analysis. Even a conductor wire has a very small resistance. You need to be careful when using the ammeter. Like stated above, the ammeter needs to be connected in series with the branch. A galvanometer is able to detect the value and direction of the current in a circuit. Just as stated above, it has a pointer attached to the armature, made from coils.

The display is calibrated to read its movement results. So what is the difference between the galvanometer and ammeter? In this way, a galvanometer can be adapted to measure larger currents than it would be able to otherwise. The shunt protects the galvanometer from damage by providing an alternate path to the flow of current. After studying physics and philosophy as an undergraduate at Indiana University-Bloomington, he worked as a scientist at the National Institutes of Health for two years.

He primarily performs research in and write about neuroscience and philosophy, however, his interests span ethics, policy, and other areas relevant to science. How Does an Ammeter Work?

The effective resistance of the ammeter is given as follows:. How to Use Analog Multimeters. How to Use a Magnet to Create Electricity. How to Read Amps on an Analog Multimeter. How to Measure Current With an Oscilloscope. How to Make a Current Transformer.