| Below is a
handy reference guide for electrical measurements, listed in
alphabetical order...
A B
C D F G
I K L M
N O P R
S T W Z
A
ACCURACY
- A measure of the difference between a
multimeter's reading to that of a primary, traceable standard.
This is usually 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.
- Example Accuracy Calculation:
1VDC Measurement on the 4V Range
|
- Displayed value
|
- 1.000V
|
- Accuracy
|
- 4V Range = (0.5%rdg+2dgt)
|
- Results
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- (1.000V x
0.5%+0.2V*) = >0.7V
*2 dgt on the 4V range corresponds to 0.2V
|
- Calculation
|
- 1.000V
>0.7V
|
- True value
|
- In a range of 0.993V~1.007V
|
- 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.
- AUTO POLARITY
- The ability of a meter to measure and
display an input of either polarity without switching the input
leads.
- AUTO RANGING
- 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.
- Go Top
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.
- Go Top
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 ohm resistance of insulation. It
degrades quickly as humidity increases.
-
- INSULATION
- 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.
- Go Top
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.
- Go top
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.
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