Glossary

NI Digital Multimeters Help (NI-DMM 18.1)

Edition Date: March 2018

Part Number: 370384V-01

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Prefixes

Symbol Prefix Value
p pico 10 -12
n nano 10 -9
µ micro 10 -6
m milli 10 -3
k kilo 10 3
M mega 10 6
G giga 10 9
T tera 10 12

Numbers/Symbols

nV nanovolts 10-9 volts
µV microvolts 10-6 volts
µΩ microohms 10-6 ohms
mΩ milliohms 10-3 ohms
MΩ megaohms 106 ohms
pA picoamps 10-12 amperes
nA nanoamps 10-9 amperes
µA microamps 10-6 amperes
mA milliamps 10-3 amperes

A

AC alternating current
accuracy How close a measurement is to the true or accepted value.
ADC analog–to–digital converter
ADE application development environment—a software environment incorporating the development, debug, and analysis tools for software development.
admittance The reciprocal of impedance.
ammeter An instrument that measures current.
aperture timeThe period during which the ADC is reading the input signal.
ATEautomated test equipment—a term typically applied to computer-based systems for testing semiconductor components or circuit card assemblies.

B

burden voltage The voltage drop caused by current flowing through a current measuring device.

C

calibration The process of adjusting an instrument in order to guarantee its accuracy.
capacitance The ability to hold an electrical charge.
CMRR common-mode rejection ratio—A measure of the capability of an instrument to reject a signal that is common to both input leads.
common-mode signal The component of an input, common to the differential input.
crest factor The ratio of the peak value of a signal to its rms value.
CSM current shunt module

D

DC direct current
DMM digital multimeter
driver Software that controls a specific hardware device such as a DAQ device or GPIB interface device.
DSP digital signal processor
DUT device under test

E

ECMRR effective common-mode rejection ratio—The sum of the CMRR and of the NMRR at a given frequency. Also, the effective rejection of a given noise signal that is applied to both input leads as it is rejected first by the CMRR capability of the instrument, and then again by its NMRR capability. This specification is most useful at the power line frequency where most of the noise resides, and is only valid for DC measurements.
EMF electromotive force
ENOD effective number of digits
EXTCLK External Clock signal.

F

frequency f—The basic unit of rate, measured in events or oscillations per second using a frequency counter or spectrum analyzer. Frequency is the reciprocal of the period of a signal.

H

handle A unique variable you use to refer to a window or other interface element in C programming.
handshaking A DMM/Switch protocol which makes it possible for two devices to synchronize operations.
HI The high (or plus) voltage input for an instrument with isolated or balanced input. The other input is the LO input.
hysteresis Lag between making a change and the effect of the change.
Hz hertz

I

I/O input/output
impedance The measure of opposition to the flow of alternating currents.
inductance The characteristic of a coil that generates a voltage due to changes in the current. An inductor creates a voltage that is the derivate of the current, while a capacitor creates a voltage that is the integral of the current.
IVI interchangeable virtual instrument

L

leakage Undesired radiation from the cable carrying a signal.
LO low—The low voltage (or minus) input of an instrument with a balanced or isolated input.
loading The effect of connecting the output of one electronic device to the input of another, such as the connection of a unit under test to an instrument. The loading effect is the difference in the output value (for example, voltage) with and without the load. To prevent loading effects, the impedance of the load must be smaller than the output impedance of the source.

M

max maximum
MC Measurement Complete—the signal emitted by a DMM after each measurement.
min minutes or minimum

N

NaN Not a Number—a digital display value for a floating-point representation of "Not a Number," as defined by the IEEE standard for binary floating point arithmetic; NaN is typically the result of an undefined operation, such as log(-1).
NI 4050 Refers to the NI PCMCIA-4050.
NI 4060 Refers to the NI PXI/PCI-4060.
NI 4065 Refers to the NI PXI/PCI/PCIe/USB-4065.
NI 4070 Refers to the NI PXI/PCI-4070.
NI 4071 Refers to the NI PXI-4071.
NI 4072 Refers to the NI PXI-4072.
NI 407x Refers to the NI 4070, NI 4071, and NI 4072.
NMRR normal-mode rejection ratio—The ability of the instrument to reject a normally (differentially) applied signal.
noise Noise comes from both external sources, such as the AC powerline, motors, generators, transformers, fluorescent lights, soldering irons, CRT displays, computers, electrical storms, welders, and radio transmitters—and internal sources, such as digital clocks, microprocessors, and switched mode power supplies. It corrupts signals you are trying to send or receive.
normal-mode signal A signal applied differentially to the DMM front panel connectors for the purpose of measuring that signal.

O

offset The unwanted DC voltage due to amplifier offset voltages added to a signal.

P

PCI Express/PCIe A version of PCI that maintains the PCI software usage model and replaces the physical bus with a high-speed serial bus serving multiple lanes.
period The period of a signal, most often measured from one zero crossing to the next zero crossing of the same slope. The period of a signal is the reciprocal of its frequency (in Hz). Period is designated by the symbol T.
PLCs powerline cycles
ppm parts per million
precision The measure of the stability of an instrument and its capability to give the same measurement over and over again for the same input signal.
PXI Express compatible module A PXI module compatible with existing PXI slots and PXI hybrid slots. PXI Express compatible modules maintain hardware and software compatibility, with the exception of local bus.

Q

quantization A process that converts continuous amplitude signals into one of a finite number of discrete amplitudes.
quantizer A device used in a quantization process.

R

resistance The resistance to the flow of electric current. One ohm (Ω) is the resistance through which one volt of electric force causes one ampere to flow.
resolution The smallest amount of input signal change that an instrument or sensor can detect. Resolution is determined by the instrument noise (either circuit or quantization noise) and the smallest change that is detectable by the display system of the instrument.
rms root mean square

S

scan list A list of connections/disconnections a switch module is programmed to make; typically used by switch modules.
SCANADV Scanner advanced—a signal emitted by a switch module when the relays have been activated and are settled.
sensitivity A measure of the smallest value of an input signal that an instrument can detect.
settling time The time required for an amplifier, relays, or other circuits to reach a stable mode of operation.
SFP Soft Front Panel
slew rate The voltage rate of change as a function of time. The maximum slew rate of an amplifier is often a key specification to its performance. Slew rate limitations are first seen as distortion at higher signal frequencies.
SSR solid–state relay
synchronous scanning A DMM/Switch protocol in which the DMM takes a measurement and generates a digital pulse—measurement complete (MC). When the switch receives the digital pulse, it advances to the next entry in its scan list.

T

tempco temperature coefficient
thermal voltages The voltage generated by the junction of dissimilar metals, usually between connections, that increases as temperature increases.
thermistor Semiconductor sensor that exhibits a repeatable change in electrical resistance as a function of temperature; most thermistors exhibit a negative temperature coefficient.

U

uncertainty The total calculated error caused by calibration error, noise, nonlinearity, offsets, temperature drift, and so on.

V

V volts
VI Virtual Instrument—a program in the graphical programming language G; so called because it models the appearance and function of a physical instrument.
voltmeter A usually direct-reading instrument used to measure voltage.
VXI VME eXtensions for Instrumentation (bus)
VXIplug&play SystemsAlliance A group of VXI developers dedicated to making VXI devices as easy to use as possible, primarily by simplifying software development.

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