Category: Measuring Devices

Measuring Devices

Bar-Graph Meters

Bar-Graph Meters

A cheap, simple kind of meter can be made using a string of light-emitting diodes (LEDs) or an LCD along with a digital scale to indicate approximate levels of current, voltage, or power. This...

Oscilloscopes

Oscilloscopes

Another graphic metering device is the oscilloscope. This measures and records quantities that vary rapidly, at rates of hundreds, thousands, or millions of times per second. It creates a “graph” by throwing a beam...

Pen Recorders

Pen Recorders

A meter movement can be equipped with a marking device to keep a graphic record of the level of some quantity with respect to time. Such a device is called a pen recorder. The...

Light Meters

Light Meters

The intensity of visible light is measured by means of a light meter or illumination meter. It is tempting to suppose that it’s easy to make this kind of meter by connecting a milliammeter...

VU and Decibel Meters

VU and Decibel Meters

In high-fidelity equipment, especially the more sophisticated amplifiers (“amps”), loudness meters are sometimes used. These are calibrated in decibels, a unit that you will often have to use, and interpret, in reference to electronic...

Frequency Counters

Frequency Counters

The measurement of energy used by your home is an application to which digital metering is well suited. A digital kilowatt-hour meter is easier to read than the pointer-type meter. When measuring frequencies of...

Digital Readout Meters

Digital Readout Meters

Increasingly, metering devices are being designed so that they provide a direct readout. The number on the meter is the indication. It’s that simple. Such a meter is called a digital meter. The main...

Watt-Hour Meters

Watt-Hour Meters

Electrical energy, as you now know, is measured in watt-hours or kilowatt-hours (kWh). Not surprisingly, a metering device that indicates energy in these units is called a watt-hour meter or a kilowatt-hour meter. The...

Wattmeters

Wattmeters

The measurement of electrical power requires that voltage and current both be measured simultaneously. Remember that in a dc circuit, the power (P ) in watts is the product of the voltage (E )...

FET Voltmeters

FET Voltmeters

A good voltmeter disturbs the circuit under test as little as possible, and this requires that the meter have high internal resistance. Besides the electrostatic-type voltmeter, there is another way to get high internal...

Multimeters

Multimeters

In the electronics lab, a common piece of test equipment is the multimeter, in which different kinds of meters are combined into a single unit. The volt-ohm-milliammeter (VOM) is the most often used. As...

Ohmmeters

Ohmmeters

If all other factors are held constant, the current through a circuit depends on the resistance. This provides us with a means for measuring resistance. An ohmmeter can be constructed by placing a milliammeter...

Voltmeters

Voltmeters

Current, as we have seen, consists of a flow of charge carriers. Voltage, or electromotive force (EMF), or potential difference, is the “pressure” that makes current possible. Given a circuit whose resistance is constant,...

Ammeters

Ammeters

A magnetic compass doesn’t make a very convenient meter. It has to be lying flat, and the coil has to be aligned with the compass needle when there is no current. But of course,...

Thermal Heating

Thermal Heating

Another phenomenon, sometimes useful in the measurement of electric currents, is the fact that whenever current flows through a conductor having any resistance, that conductor is heated. All conductors have some resistance; none are...

Electrostatic Deflection

Electrostatic Deflection

Electric fields produce forces, just as magnetic fields do. You have noticed this when your hair feels like it’s standing on end in very dry or cold weather. You’ve heard that people’s hair really...