Glossary

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Glossary ABSORPTION WAVEMETER - A device used for measuring frequency, consisting of a tuned circuit or cavity that is loosely coupled to the frequency being measured. Maximum energy is absorbed at the resonant frequency. BOLOMETER - An rf detector that converts rf power to heat, which causes a change in the resistance of the material used in the detector. This change in resistance varies in proportion with the amount of applied power and is used to measure the amount of applied power. CALORIMETER - A device that measures rf power by measuring the heat the rf power generates.

CAVITY WAVEMETER - An instrument used to measure microwave frequencies. The resonant frequency of the cavity is determined by its inside dimensions. COAXIAL-LINE WAVEMETERS - A shorted section of a coaxial line used to measure rf frequencies. It is calibrated in either wavelength or frequency. CROSS MODULATION - An intermodulation condition that occurs when a carrier is modulated by an undesired signal. CURRENT PROBE - An inductive device used for measuring the current in a conductor. Probes are designed to be clamped around the insulated conductor.

CURRENT TRACER - An inductively coupled device used for tracing current paths to determine the cause of low-impedance faults on a printed-circuit board. DECADE RESISTOR (DECADE RESISTANCE BOX) - It typically has two or more sections, each containing 10 precision resistors wired to selector switches. A piece of test equipment that provides a ready source of various resistances for engineering and measurement applications. DECIBEL (dB) - A standard unit for expressing relative power levels as the ratio of power out to power in.

dBm - A unit used to express power levels above or below a l-milliwatt reference level at a designated load impedance (usually 600 ohms). NEETS Module 21, NAVEDTRA 14193A

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DIFFERENTIAL VOLTMETER - A precision voltmeter that measures an unknown voltage by comparing it to a precision internal-reference voltage supply. ELECTROSTATIC-DISCHARGE SENSITIVE (ESDS) DEVICE - Electronic components that are susceptible to damage from static charges. FIBER OPTICS - Conductors that are usually constructed of plastic or glass fibers that readily pass light. Used primarily for transmission of high-speed data over relatively short distances. FREQUENCY DEVIATION - Refers to the difference between the carrier frequency of an fm signal and the instantaneous frequency of its modulated wave.

FREQUENCY DOMAIN - A plot of frequency versus amplitude as shown by a spectrum analyzer display. FREQUENCY RESPONSE - (I) The ability of a component or device to operate over a portion of the frequency spectrum. (2) In reference to test equipment, that portion of the frequency spectrum that the test equipment is capable of sensing and measuring accurately. GALVANOMETER - A meter used to measure small values of current by electromagnetic or electrodynamic means. IMPEDANCE ANGLE METER - A device that measures circuit impedance by comparing the phase angle between voltage and current.

INSERTION LOSS - The difference between the amount of power applied to a load before and after the insertion of a device in the line. INTEGRATED CIRCUIT (IC) - (1) A circuit in which many elements are fabricated and interconnected by a single process (into a single chip), as opposed to a nonintegrated circuit in which the transistors, diodes, resistors, and other components are fabricated separately and then assembled. (2) Elements inseparably associated and formed on or within a single substrate. INTERMODULATION DISTORTION - Nonlinear distortion characterized by the appearance (at the system output) of frequencies equal to the sums and differences of two or more frequencies present at the input.

LOAD - (I) A device through which an electric current flows that changes electrical energy into another form. (2) Power consumed by a device or circuit in performing its function. NEETS Module 21, NAVEDTRA 14193A

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LOGIC CLIPS - A device that can be clipped onto an in-circuit, dual-in-line package (DIP) logic IC to determine the logic state of each pin of the IC. LOGIC PROBE - A hand-held probe used to determine the logic state (high or low) of test points in a logic circuit. A logic high is represented by a lit indicator light on the probe. LOGIC PULSER - A hand-held probe used to pulse, or change the logic state, of in circuit logic ICs. METROLOGY CALIBRATION (METCAL) PROGRAM - A Navy calibration program designed to ensure the accuracy of test equipment through comparisons with calibration laboratory standards of known accuracy.

MICROPHONICS - Electrical noise caused by the mechanical motion of the internal parts of a device. The term is usually associated with vacuum tubes. MODULATION INDEX - When a sine wave is used to modulate an fm signal, the ratio of the frequency deviation to the frequency of the modulating wave. NATIONAL BUREAU OF STANDARDS (NBS) - A bureau of the United States government that is responsible for maintaining the nation's electrical and physical standards. The accuracy of all calibrated test equipment is traceable to NBS through the Navy's METCAL program.

OPTICAL TIME-DOMAIN REFLECTOMETER (OTDR) - A piece of test equipment used to test a fiber-optic cable for such things as attenuation, localized losses, and defects. It transmits an optical pulse (usually a laser) into the fiber-optic cable and analyzes the resulting reflections in terms of amplitude versus distance. PARALLAX ERROR - The error in meter readings that results when you look at a meter from some position other than directly in line with the pointer and meter face. A mirror mounted on the meter face aids in eliminating parallax error.

PARASITIC - In electronics, an undesirable frequency in an electronic circuit. Usually associated with vacuum-tube amplifiers and oscillators. PERCENT OF MODULATION - In AM signals, the ratio of half the difference between the maximum and minimum amplitudes of a modulated wave to its average amplitude. RF IMPEDANCE BRIDGE - A piece of test equipment used for measuring the combined resistance and reactance of a component, piece of equipment, or system at rf frequencies. NEETS Module 21, NAVEDTRA 14193A

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SENSITIVITY - In reference to test equipment, the ratio of the response of the test equipment to the magnitude of the measured quantity. Sometimes expressed indirectly by stating the property by which sensitivity is computed (e.g., ohms per volt). STANDARD - An exact value of an electrical quantity (established by international agreement), which serves as a model for measurement of that quantity. STANDING WAVE - The distribution of voltage and current along a transmission line formed by the incident and reflected waves, which has minimum and maximum points on a resultant wave that appears to stand still.

STROBOSCOPE - An instrument that allows viewing of rotating or reciprocating objects by producing the optical effect of a slowing or stopping motion. SWEPT-FREQUENCY TESTING - Testing the frequency response of a component or system by applying an rf signal, in which the frequency is varied back and forth through a set frequency range at a steady rate, to the input of a device. The output is then monitored to determine the amplitude of the output with respect to frequency. THERMISTOR - (1) A semiconductor device in which the resistance varies with temperature. (2) A type of bolometer characterized by a decrease in resistance as the dissipated power increases.

TIME-DOMAIN REFLECTOMETER - A piece of test equipment used to test a transmission line for defects, such as shorts and opens. It transmits an electrical pulse into the transmission line and analyzes the resulting reflections in terms of amplitude versus distance. TRAIC - A three-terminal device that is similar to two SCRs back-to-back with a common gate and common terminals. Although similar in construction and operation to the SCR, the Triac controls and conducts current flow during both alternations of an ac cycle.

TUNING FORK - A two-pronged mechanical device that is designed to vibrate only at its natural frequency. In electronics, it is used primarily to determine the correct speed of a motor. UNIJUNCTION TRANSISTOR (UJT) - A three-terminal, semiconductor device with a negative-resistance characteristic that is used in switching circuits, oscillators, and Waveshaping circuits. VOLUME UNIT (VU) - Unit of measurement of a complex audio signal such as voice or music. A 0 level is referenced to 1 milliwatt of power into a 600-ohm load.

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WAVEMETERS - (1) Calibrated resonant circuits that are used to measure frequency. (2) An instrument for measuring the wavelength of an rf wave. ZENER DIODE - A pn-junction diode designed to operate in the reverse-bias breakdown region.