Extech Instruments 7470 Operation Manual page 7

milliamperes, microamperes, nanoamperes, or picoamperes. Symbol = I
Dielectric:
An insulating material that is positioned between two conductive materials in such a way
that a charge or voltage may appear across the two conductive materials.
Direct Current, DC:
Current that flows in one direction only. The source of direct current is said
to be polarized and has one terminal that is always at a higher potential than the other.
Frequency: The number of cycles an AC waveform repeats over time. Usually
given in Hertz (Hz).
Ground: Refers to the point of low potential in a circuit to which all other voltages are
referenced. May or may not be tied to the earth. Also referred to as Earth.
Hot: Used to refer to the test lead or output side of an instrument that is at high
potential.
Impedance: The property of capacitive or inductive items to limit certain frequencies.
Insulation: Gas, liquid or solid material which has a volume resistivity of at least 10 12
Ω-cm and is used for the purpose of restricting current flow between conductors.
Leakage: AC or DC current flow through insulation and over its surfaces. Current
flow is directly proportional to voltage. The insulation is thought of as a constant
impedance unless breakdown occurs.
Neutral: The point of low potential in a circuit to which all other voltages are
referenced. Also known as Common.
Peak Current: The maximum amplitude of an AC current waveform. For a sinusoid,
1.414 x the RMS value.
Power: The amount of work performed by an energy source over time, given in Watts
(W).
PF (Power factor): Power Factor = W/VA where W =Watts (Real Power) and VA
=Volts x Amps (apparent power). It is important to note that the closer the power
factor is to "1" the more resistive the DUT is. The closer the power factor is to 0 the
more reactive (inductive or capacitive) the DUT is.
Reactive Current: The current component due to the reactive impedance of a load.
Also called imaginary current.
Real Current: The current component due to the resistance of a load.
Resistance: The property of a substance that impedes current and results in the
dissipation of power in the form of heat. The practical unit of resistance is the ohm (Ω).
Symbol = R
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