Below is a handy reference guide for electrical measurements, listed in alphabetical order...

A

ACCURACY

A measure of the difference between a multimeter's reading to that of a primary, traceable standard.  This is ususlly specified as a percent of reading plus a percentage of range (percentage of range is often referred to as display counts or digits).  The percentage of reading is most significant when the reading is close to full scale, while the percentage of range is most significant when the reading is a small fraction of full scale.

A/D (ANALOG-TO-DIGITAL) CONVERTER

An electronic device, often an integrated circuit, that converts an analog voltage to a digital value. All digital multimeters use an A/D converter to convert the input signal into digital information.

AUTOPOLARITY

The ability of a meter to measure and display an input of either polarity without switching the input leads.

AUTORANGING

The ability of a meter to switch among ranges automatically. The ranges are usually in decade steps.

AVERAGE RESPONDING

A measurement where the displayed value is proportional to the average of the absolute values of all input waveforms within a specified frequency range. It is calibrated in the rms value of a sine wave.

B

BANDWIDTH

The highest frequency signal component that can pass through input amplifiers and/or filters without being attenuated.

 

BIPOLAR

An analog signal range that includes both positive and negative values.

C

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.

CAPACITANCE METER

Any meter that measures capacitance.

COLD JUNCTION

The junction in a thermocouple circuit that is held at a stable known temperature. Also known as reference junction.

 

COLD-JUNCTION COMPENSATION

A method of compensating for ambient temperature variations in thermocouple circuits.

 

COMMON MODE VOLTAGE

A voltage between input low and chassis ground of a meter.

 

CONNECTION PATH

The cables, connectors, switch cards, etc. between the device under test (DUT) and themeter. Its major parts are the conductors making the connection and the insulators isolating the conductors from the rest of the world.

 

CONVERSION

A process where a signal is changed from an analog to digital (A-D) representation, or digital to analog (D-A).

 

CONVERSION RATE

The rate at which sampled analog data is converted to digital data or digital data is converted to analog data.

 

CREST FACTOR

The ratio of the peak value to the root-mean-square (rms) value of a waveform.

D

DIFFERENTIAL INPUTS

An analog input with two input terminals, neither of which is grounded, whose value is the difference between the two terminals.

DMM

An electronic meter that measures voltage, current, resistance, or other electrical parameters by converting the analog signal to digital information and display. The typical five-function DMM measures DC volts, DC amps, AC volts, AC amps, and resistance.

 

DUTY RATIO

The ratio of pulse width to repetition period. Also known as Duty Cycle.

 

DYNAMIC DATA EXCHANGE (DDE)

A Microsoft Windows standard mechanism for communication between programs. It allows your application to send and share data with other applications such as spreadsheets.

F

FLOATING

The condition where a common mode voltage exists between an earth ground and the meter or circuit of interest. (Low of circuit is not at earth potential.)

FOUR-TERMINAL RESISTANCE MEASUREMENT

A measurement where two leads are used to supply current to the unknown and two different leads are used to sense the voltage drop across the resistance.

G

GROUND

A common reference point for an electrical system.

I

IEEE

Abbreviation for Institute of Electrical and Electronics Engineers.

 

INPUT IMPEDANCE

The shunt resistance and capacitance (or inductance) as measured at the input terminals, not including effects of input bias or offset currents.

 

INSULATION RESISTANCE

The ohmic resistance of insulation. It degrades quickly as humidity increases.

 

INSULATON

A material that does not significantly conduct electrical current.

 

INTEGRATING CONVERSION

An analog to digital conversion process where the output results in a digital representation of the integral of the input signal over a specified time interval.

K

KELVIN CONTACTS

A means for testing or making measurements in electronic devices and circuits, particularly when low values 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 meter. The effect of resistance in the leads is thus eliminated.

L

LCZ METER

Inductance (L), capacitance (C), impedance (Z) meter. A general purpose meter for measuring component L, C. and Z. Sometimes called LCR meter.

 

LEAKAGE CURRENT

Leakage current is any unwanted current that flows when test voltage is applied. The ideal leakage current is zero. Leakage currents can originate in meters, cables, or the device being tested. Even high resistance paths between low current conductors and nearby voltage sources can generate significant leakage currents.

 

LINEARITY

The maximum deviation from a straight line between meter readings at zero and full range. It is expressed in percent.

M

MAXIMUM ALLOWABLE INPUT

The maximum DC plus peak AC value (voltage or current) that can be applied between the high and low input measuring terminals without damaging the meter.

 

MULTIPLEX

Connecting one meter to multiple devices under test or multiple meters to one device under test.

N

NOISE

An undesirable electrical signal from an external source such as an AC power line, motors, generators, transformers, fluorescent lights, CRT displays, computers, radio transmitters, and others.

 

NORMAL MODE REJECTION RATIO (NMRR)

The ability of an meter to reject interference (usually of line frequency) across its input terminals. Usually expressed in decibels at a frequency.

 

NORMAL MODE VOLTAGE

A voltage applied between the input high and input low terminals of an meter.

O

OVERLOAD PROTECTION

A circuit that protects the meter against excessive current at the input terminals.

P

PEAK RESPONDING

A measurement where the displayed value is equal to the peak value of the input signal.

R

RANGE

A continuous band of signal values that can be measured or sourced. In bipolar meters, range includes positive and negative values.

 

RATED ACCURACY

The limit that errors will not exceed when the meter is used under specified operating conditions. It is expressed as a percentage (of input or output) plus a number of counts.

 

RATIO MEASUREMENT

The measurement of a signal input with relation to an external reference input.

 

READING

The displayed number that is proportional to the measured magnitude of the input signal.

 

READING RATE

The rate at which the displayed number is updated.

 

RELIABILITY

The ability of a device to perform within the desired range over a measured period of time.

 

REPEATABILITY

The ability of a meter to measure the same input to the same value over a short period of time and over a narrow temperature range.

 

RESOLUTION

The smallest value of input (or output) signal, other than zero, that can be measured (or sourced) and displayed. Also called sensitivity or minimum resolvable quantity.

 

RMS RESPONDING

A measurement where the displayed value is equal to the root-mean-square (rms) of the input signal, for all input waveforms having components within the specified frequency range and crest factor limit.

S

SHORT-TERM ACCURACY

The limit that errors will not exceed during a 24-hour period of continuous operation. Unless specified, no zeroing or adjustments of any kind are permitted. It is expressed as a percentage of reading plus a number of counts over a specified temperature range.

 

SIGNAL/NOISE RATIO

The ratio of the maximum signal that can be measured to the level detected with no signal present (noise level). It is expressed in decibels.

 

SINGLE-ENDED

The condition where the low terminal of a two-terminal meter is connected to a specific reference point, such as power line common, earth ground, or circuit common.

T

THERMOCOUPLE

A temperature sensor created by joining two dissimilar metals. This junction creates a small voltage as a function of the temperature.

 

TTL

Abbreviation for transistor-transistor-logic. A popular logic circuit family that uses multiple-emitter transistors. A low signal state is defined as a signal 0.8V and below. A high signal state is defined as a signal +2.0V and above.

W

WARM-UP TIME

The time required after power is applied to a meter to achieve rated accuracy at referenced conditions.

Z

ZERO OFFSET

The reading (desired or undesired) that occurs when the input terminals of a meter are shorted.