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1、PEC电气工程专业英语证书考试-Glossary of Electrical Engineering Terms5AC Signal: The time variant portion of a voltage or current.Alternate Sweep: A vertical mode of operation for a dual-trace oscilloscope. The signal from the second channel is displayed after the signal from the first channel. Each trace has a
2、complete trace, and the display continues to alternate. This mode is used for SEC/DIV settings of less than 1 ms/div (faster than 1 kHz).Alternating Current (AC): An electric current whose instantaneous value and direction change periodically. The term usually refers to sinusoidally shaped current o
3、r voltage waves.Amplitude: Height of a waveform above ground (1/2 peak-peak value)Attenuation: The decrease in signal amplitude during its transmission from one point to another.Bandwidth: The oscilloscope frequency range within which performance of a particular characteristic falls within specified
4、 limits, commonly defined as the difference between the upper and lower frequency at which the response is .707 (-3dB) of the response at the reference frequency.Blanking: The process of making the trace, or parts of a trace, invisible.Bypass: A capacitor placed from a dc signal to ground will remov
5、e any ac component of the signal by creating an ac short circuit to ground.Calibration: The process of comparing an instrument or device against a standard to determine instrument accuracy or to make a correction.Capacitance: The property of a system of conductors to and dielectrics which enables th
6、e system to store electricity when a voltage is applied between the conductors, expressed as a ratio of the electrical charge stored and the voltage across the conductors. The basic unit is the Farad .Capacitor: A device consisting of two conducting materials separated by an insulating material (die
7、lectric), which can store an electrical charge when a potential difference exists between the two conductors.Cathode-ray-tube: An electron-beam tube in which the beam can be focused to a small cross-section on a luminescent screen and varied in both position and intensity to produce a visible patter
8、n.Chop: A vertical mode of operation for dual-trace oscilloscopes in which the display is switched between the two channels at some fixed rate. This mode should be used for slow sweep rates.Common: The potential level serving as ground for the entire circuit.Comparator: A component which satisfies,
9、for input Vin and reference voltage Vr the equationsif Vin Vr then Vout = Vcc.if Vin Vr then Vout = -Vcc.Compensation: The controlling elements that compensate, or, offset the undesirable characteristics of the process being controlled in a system.Coupling: The association of two or more circuits or
10、 systems in such a way that power or information may be transferred from one to the other.Crosstalk: Leakage of signal from one source into another.Current: The rate of change of charge (electrons) or flow of charge/second (dQ/dt) through a circuit.Detent: A stop or other device (such as a pin or le
11、ver) on a ratchet wheel. Switch action is typified by a gradual increase in force to a position at which there is an immediate and marked reduction in force.Diode: The diode is the simplest and most fundamental non-linear circuit element. It is a two terminal device which only allows current to flow
12、 in one direction.Direct Current (DC): An electric current that flows in only one direction with essentially constant value.Display: The visual representation of a signal on a CRT screen.Distortion: An undesired change in waveform.Dual Channel (Dual-trace) Oscilloscope: An oscilloscope that has two
13、independent input connectors and vertical sections and can display them simultaneously.Dual-sweep (Dual-timebase) Oscilloscope: An oscilloscope that can display a signal with two independent SEC/DIV settings.Duty Cycle: The ratio of the lengths of the positive to negative halves of a waveform expres
14、sed in percentages.Farad Unit of measure of capacitance. Named after Farad.Feedback: Voltage from the output of a circuit is channeled (or fed) back into the input of the circuit.Focus: The oscilloscope control that converges the CRT electron beams to produce a sharp display.Free-running Trace: A tr
15、ace that is displayed without being triggered and either with or without an applied signal.Frequency: The inverse of time (1/seconds). How often an event occurs within a second.Graticule: The CRT grid lines that facilitate the location and measurement of oscilloscope traces.Ground: 1. A conducting c
16、onnection that by which an electric circuit or equipment is connected to the earth to establish and maintain a reference potential level. 2. The voltage reference point in a circuit.Hertz: Unit of frequency, one cycle per second.Hysteresis: An output voltage Vcc does not change to -Vcc until the input increases above B*Vcc, B being a const
