Glossary of Test Equipment Terminology

When dealing with technical equipment such as test, analysis and measurement instrumentation it's always helpful to have a firm understanding of the terminology. Please note that this glossary of definitions is a very much a work in progress and will be regularly updated.

Ammeter - A meter which measures the flow of electrical current in amperes or amps. Ammeters are sometimes referred to as ampmeters or amp meters.

Attenuator - A device which attenuates or decreases the strength or amplitude of an electrical signal. One common example of an attenuator is a volume control.

Autocollimator - An instrument which combines the functions of a telescope and a collimator. An autocollimator measures very small deviations in a light beam.

Autosampler - An autosampler is a liquid sampler which takes samples automatically based on either a programmable time schedule or based on conditions that are read from sensors such as flowmeters. For instance, an autosampler could take a sample when a flowmeter indicates a heavier flow of water than normal, such as after a rainstorm.

Cable Locator - An instrument used to locate underground cables, wiring and pipes. Cable locators can be used not only to locate the cabling but to estimate the depth of the wiring. They are essentially specialized metal detectors.

Calibrator - A device used to calibrate a precision instrument. Calibration consists of comparing measurements of the instrument with a standard and making adjustments to bring the instrument into compliance with that standard. Proper use of a calibrator ensures that the instrument is as accurate as possible.

Chart Recorder - A device which records an electrical or mechanical input trend onto a paper chart. An electrocardiogram (ECG or EKG) or a lie detector are good examples of such a device.

Clamp Meter - An ammeter which allows you to measure electrical current without having to disconnect the wiring to take the measurement. A clamp meter measures the current through the wire insulation.

Collimator - A device which takes a beam of waves or particles and causes it to become more aligned or parallel. In essence a collimator produces a parallel beam.

Curve Tracer - A type of test equipment which provides a graphical display of the voltage versus current of an electronic component. They alre also occasionally used to measure other electronic parameters. Many curve tracers are designed as plug-ins to be used in conjunction with oscilloscopes.

Data Logger - A data logger or data recorder is the electronic or computer equivalent of a chart recorder. Instead of logging the data on a paper chart the data is displayed on a screen or stored in a file or database.

Disturbance Analyzer - An instrument which measures AC and DC power disturbances such as voltage outages, voltage surges, and voltage drops or sags. Some disturbance analyzers in addition to taking measurements also record and print the results.

Flow Meter - A meter which measures the rate of flow of a liquid or gas past a given point or location.

Frequency Counter - An electronic instrument which displays the frequency of a signal. Frequency counters typically work by the means of a counter which counts the number of events which occur within a specified period of time.

Frequency Standard - An oscillator which is used as a reference source for calibrating frequency measurements. A frequency standard generates a very precise and accurate fundamental frequency. The harmonics of this fundamental frequency are then used to supply reference points for calibration purposes.

Function Generator - A type of signal generator which generates an electronic waveform. Examples of common waveforms include sine, square, triangle and sawtooth waveforms.

GPIB - GPIB is short for General Purpose Interface Bus, a digital bus specification which allows automated test equipment devices to communicate with each other. It was originally known as HP-IB (Hewlett Packard Interface Bus) and is also currently known as IEEE-488.

Hipot Tester - A hipot or hypot tester is a type of electronic test equipment which allows you to check the quality of the electrical insulation in an electrical cable, circuit board, transformer or any other electrical device. Hipot is short for high potential voltage. A hipot tester is used to verify that no electricity will flow through the insulation. It works by generating a high voltage between the circuits and checking by the means of a meter to ensure that no current flows between the two points.

HP-IB - HP-IB is short for Hewlett Packard Interface Bus. HP-IB is a bus specification which was created to facilitate communication between electronic testing devices. It is now known as GPIB or IEEE-488.

Logic Analyzer - A logic analyzer is used to test digital circuits or systems. A logic analyzer displays the logic levels (0 or 1) of signals in the circuit. The logic analyzer's built-in software then converts the data into various formats which a technician can use to debug failures in the system. See "How Does A Logic Analyzer Work?" for more information.

Manometer - An instrument which measures pressure.

Optical Fiber - A type of fiber made of glass or plastic which is designed to allow light to travel along its length. A fiber optic cable is comprised of many optical fibers.

Optical Time Domain Reflectometer - An OTDR is a device used in the fiberoptic and communications industry to find faults, bends and splices in fiber optic cabling. An OTDR works by injecting a series of optical pulses into the fiber which are then reflected back and measured for deviations in the light wave.

Oscillator - An electronic circuit which generates a repeating electronic signal such as a sine wave or a square wave. Oscillators are used in devices such as function generators and frequency standards.

Oscilloscope - An electronic test instrument which renders electrical signals or waveforms as a visible wave on a fluorescent cathode-ray tube screen. The wave is shown on a graph. The horizontal axis indicates time and the vertical axis shows the amplitude at that exact point. An oscilloscope lets you see how a signal varies over time. A multiple trace oscilloscope allows you to monitor multiple waveforms at the same time so you can make timing measurements or a phase comparison. See "How Does an Oscilloscope Work?" for more information.

Signal Generator - A type of electronic equipment which generates a precisely calibrated repeating signal. The signal can be analog or digital and can be adjusted by frequency, waveform, output voltage, modulation and impedance. Signal generators are used for testing as well as designing electronic equipment.

Spectrum Analyzer - A spectrum analyzer or spectral analyzer measures an electrical, optical or acoustic waveform and displays the frequency response curve in real time. See "How Does a Spectrum Analyzer Work?" for more information.

Thermometer - An instrument which measures temperature.

Time Domain Reflectometer - A Time Domain Reflectometer (or TDR for short) is a device which allows you to locate faults in metal cables. A TDR works by generating an electrical pulse which is transmitted through the cable. When the pulse reaches a fault point or the end of the cable it is reflected back to the TDR. The TDR then takes a measurement of the time that it took for the signal to travel through the cable and back. This measurement is then converted into the distance to the fault point. It's actually very similar to how a radar works.

Universal Counter - A frequency counter which in addition to measuring frequency also measures other parameters such as time interval and period. They are sometimes also referred to as universal frequency counters.

Universal Disturbance Analyzer - A disturbance analyzer which not only measures power disturbances but also has the capacity to measure disturbances in radio frequency, temperature, humidity and more, by the means of individual plug-in modules. As well as taking measurements universal disturbance analyzers generally also monitor, record and print the results.

Vacuum Gauge - An instrument which measures the pressure in a vacuum.

Vectorscope - A specialized type of oscilloscope which is used for video and audio analysis. A vectorscope can display information about the chrominance or color portion of a video signal as well as measure the difference between stereo audio channels.

Vibration Meter - A device which measures the amount of vibration present in a piece of machinery. Vibration meters are typically used to locate precise areas of vibration and noise in equipment such as motors, pumps, gearboxes and compressors.

Waveform Monitor - A specialized type of oscilloscope which displays a graph of a video signal. Waveform monitors display the amplitude or voltage on the vertical axis and time on the horizontal axis.