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Glossary and Useful Definitions
Autoranging: The ability of an instrument to switch among ranges automatically. The ranges are usually in decade steps.
Bias Voltage: A voltage applied to a semiconductor to establish a reference level for the operation of the device during testing.
Capacitance: In a capacitor or system of conductors and dielectrics, the property that permits the storage of electrically separated charges when potential differences exist between the conductors. Capacitance is related to charge and voltage as follows: C = Q/V, where C is the capacitance in farads, Q is the charge in coulombs, and V is the voltage in volts.
Cold Switching (or Dry Switching): Closing relay or switch contacts before applying voltage and current and removing voltage and current before opening the contacts. (Contacts do not make or break current.)
Compliance Voltage: The maximum output voltage of a constant current source.
Conductance (G): The reciprocal (1/R) of resistance, usually specified in Siemens (S).
Four-Terminal Resistance Measurement: See Kelvin terminals.
GPIB: General Purpose Interface Bus: A standard for parallel interfaces.
GR874: Hermaphroditic (no male and female) connector developed by GenRad that eliminates the need for gender-changers. For more info, check HERE.
IEEE: Institute of Electrical and Electronics Engineers.
IEEE-488: See GPIB.
Kelvin Terminals (Four-Terminal Resistance Measurement): A means for testing or making measurements in electronic devices and circuits, particularly when small impedances are being measured. Two sets of leads are used at each test point, similar with respect to thickness, material and length; one set carries the test signal and the other connects with the measuring instrument. The effect of resistance in the leads is thus eliminated.
Power Coefficient of Resistance: A change in resistance with a change in applied power, expressed as a percentage or ppm of readings per watt.
ppm, Parts per Million: A measure of small ratios, usually applied to calibrations or accuracies. 1 ppm = 10-6 or .0001%, and 1% = 10,000 ppm.
rms: Root Mean Square of the input signal, indicative of power.
RTD, Resistance Temperature Detector: A sensor which will detect temperature by a varying resistance. IET offers manual or programmable RTD simulators.
Temperature Coefficient: A change in a quantity, such as resistance, with a change in temperature, expressed as a percentage or ppm of reading per degree change in temperature.
Thermal emf: Voltages resulting from temperature differences within a measuring circuit or when conductors of dissimilar metals are joined together. See p. 3 for more details.
Two-Terminal Resistance Measurement: A measurement where the same current flows through the unknown and the test leads. See Kelvin Terminals.
Voltage Coefficient of Resistance: A change in resistance with a change in applied voltage, expressed as a percentage or ppm of readings per volt. This generally applies to very high resistance values only, over 10 G-.
Zero Offset: The reading (desired or undesired) that occurs when the input terminals of a measuring instrument are shorted.
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