02-05-2014, 10:43 AM
Cathode Ray Oscilloscope
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CRO
The cathode ray oscilloscope (CRO) is a device that allows the amplitude of electrical signals, whether they are voltage, current; power, etc., to be displayed primarily as a function of time.
The oscilloscope depends on the movement of an electron beam, which is then made visible by allowing the beam to impinge on a phosphor surface, which produces a visible spot.
Oscilloscope Block Diagram:
General oscilloscope consists of the following parts:
1. Cathode ray tube (CRT)
2. Vertical deflection stage
3. Horizontal deflection stage
4. Power supply
CRO measurements
Amplitude is the maximum voltage reached by the signal. It is measured in volts, V
Peak voltage is another name for amplitude
Peak-peak voltage is twice the peak voltage (amplitude). When reading an oscilloscope trace it is usual to measure peak-peak voltage.
Time period is the time taken for the signal to complete one cycle.
It is measured in seconds (s), but time periods tend to be short so milliseconds (ms) and microseconds (µs) are often used. 1ms = 0.001s and 1µs = 0.000001s.
Frequency is the number of cycles per second.
It is measured in hertz (Hz), but frequencies tend to be high so kilohertz (kHz) and megahertz (MHz) are often used. 1kHz = 1000Hz and 1MHz = 1000000Hz.
Lissajous Patterns
Lissajous figures are sometimes used for the measurement of phase. They are produced in an oscilloscope by connecting one signal to the vertical trace and the other to the horizontal trace.
Cathode-ray oscilloscopes (CROs) provide a simple means for measuring the phase difference between two sinusoidal signals.