Electrical Instruments - Meters
Vocabulary Term
Definition
ammeter
A device used to measure current. An ammeter is connected in
series to a circuit.
analog
A mode of display using a scale and pointer. Analog meters allow
interpolation and give a sense of quantity relative to other possible
values.
cathode-ray tube
An analog display device that uses a vacuum tube to generate
images on a layer of phosphors driven by an electron beam.
current
The flow of electricity. Current is measured in amps.
D'Arsonval movement
An action caused by electromagnetic deflection, using a coil of
wire and a magnetized field. When current passes through the coil,
a needle is deflected.
decibel
A unit used to convey the intensity of sound, abbreviated as dB.
decibel meter
A device used to measure the intensity of sound. Many DMMs
have a decibel meter function.
diode
A two-terminal semiconductor device that allows current to flow
through it in only one direction. A diode has a low resistance to
electrical current in one direction and a high resistance in the other
direction.
directly proportional
A relationship where a number increases or decreases together with
another number at the same ratio. Directly proportional is the
opposite of inversely proportional.
DMM
The abbreviation for a digital multimeter.
dynamometer movement
An action using two stationary coils to measure power output. One
coil is energized by voltage, the other by amperage, producing
deflection.
efficiency
A measure of the energy output of a system versus the total energy
supplied to it.
electromagnet
A magnet which is charged by a current-carrying coil wound
around it. Electromagnets can produce much larger magnetic field
than permanent magnets.
electromagnetic deflection
The ability of an electrical current to displace a magnetic field.
Electromagnetic deflection reacts to and is able to measure the
magnitude or intensity of a field.
energy
The ability to do work. Energy is measured in kWh and expressed
as the product of power and time.
full scale deflection
Moving the indicator all the way up without hitting the stop pin.
The more sensitive the instrument, the less input it takes to reach
full scale deflection.
galvanism
An effect whereby electrical current causes mechanical motion.
Galvanism reacts to polarity and accurately measures magnetic
flux directionally.
Electrical Instruments - Meters
Vocabulary Term
Definition
galvanometer
A basic device for measuring a small electric current by means of a
mechanical motion derived from electromagnetic forces produced
by the current.
International Electrotechnical Commission
An organization that provides conformity assessment for
government, business, and society for all electrical, electronic and
related technologies.
interpolation
Estimating the value of a quantity from known values on either
side of it. Users of analog meters often must interpolate data on the
readout.
kilowatt-hour meter
The more common range of a watt-hour meter. Because energy is
usually measured over an extended period of time, the use of
power is expressed in kilowatts.
leads
The red and black conductive wires attached to meters and
connected to circuits.
lockout/tagout
A method of protecting employees from accidental machine startup
through proper locking and labeling of machines that are
undergoing maintenance.
multimeter
A device that combines the functions of an ammeter, voltmeter,
and ohmmeter. A multimeter is the most versatile and common
meter used today.
multirange
A meter able to measure wide ranges using fixed internal series
resistances. A dial on the meter makes it easy to switch to the
different ranges.
National Electrical Manufacturers Association
An organization that defines a product, process, or procedure with
reference to safety, performance, and testing.
National Fire Protection Association
The organization that produces the National Electric Code. The
NFPA outlines the minimum safety requirements for any electrical
installation.
National Institute of Standards and Technology
A federal agency that promotes innovation and industrial
competitiveness by developing better standards and technology.
Ohm's Law
The universal truth stating that it takes one volt to push one amp
through one ohm.
ohmmeter
A device used to measure resistance. A resistor must be removed
from a circuit to attach an ohmmeter.
oscilloscope
A device that produces a visual trace of voltage or current wave
shapes, generally on a cathode ray tube.
perfect conductor
A material that allows a completely free flow of electrons. A
perfect conductor has zero resistance.
perfect insulator
A material that does not allow any flow of electrons. A perfect
insulator has infinite resistance.
Electrical Instruments - Meters
Vocabulary Term
Definition
polarity
Having two oppositely charged poles, one positive and one
negative. Polarity determines the direction in which current tends
to flow.
power
The rate at which a device converts electrical energy into another
form, such as heat or light. Power is measured in watts.
rectifier
A device, such as a diode, that converts alternating current to direct
current. Rectifiers allow meters to measure both DC and AC.
resistance
The opposition to current flow. Resistance is measured in ohms.
resistor
A device that restricts current flow and produces work, such as
heat or light.
sensitivity
The degree of response of an instrument to an incoming signal. A
more sensitive meter can make more exact measurements.
shunt
A low-resistance connection between two points in an electric
circuit that forms an alternative path for a portion of the current.
Shunts allow meters to produce accurate readings in a much wider
range.
solenoid
A cylindrical coil of wire that generates a force when an electrical
current is applied.
solid state relay
Circuitry that has replaced D'Arsonval movement in digital meters.
SSR is faster and does not wear out.
voltage
A measure of electrical pressure or potential known as
electromotive force. Voltage is measured in volts.
voltmeter
A device used to measure voltage. Voltmeters connect in parallel to
a circuit.
VOM
Abbreviation for volt, ohm, milliammeter, the most common setup
of a multimeter. Because of this, multimeters are often known as
VOMs.
watt-hour meter
A device used to measure electrical energy.
wattmeter
A device used to measure electrical power.
Wiggins solenoid meter
A testing device that vibrates when a current is detected. Also
called a "wiggy", it is small and durable, but may be replaced by
more versatile and safer DMMs.