Understanding Oscilloscopes: A Comprehensive Guide
Description
The oscilloscope is an electronic measuring instrument that plots electrical signals. Although it directly measures only voltages, it can indirectly measure a large number of physical quantities, as long as they can be associated with a voltage directly proportional to the quantity of interest.
Unlike a voltmeter, oscilloscopes can visualize the behavior of a signal over time. The screen, technically called a cathode ray tube (CRT), shows the voltage signal versus time.
The main parts of an analog oscilloscope are:
– CRT
– Vertical Section
– Horizontal Section
– Power Supply
Cathode Ray Tube
– To achieve synchronization, the oscilloscope has a Trigger Level control, which determines the voltage threshold the measured signal must reach for the beam to start sweeping across the screen. The sample is taken from the vertical amplifier.
– A switch allows disconnecting the sync pulses from the vertical amplifier and introducing external ones. The signal can also be synchronized with standard frequencies (e.g., 50 Hz, TV horizontal sync).
– Horizontal Input: Using the INT/E (Internal/External) switch, the horizontal oscillator can be switched off, stopping the internal horizontal sweep. This allows introducing an external signal to the horizontal deflection plates through a dedicated BNC connector. This input also features AC-DC-GND switching and a V/div attenuator. This input is typically used to introduce two alternating signals (e.g., sinusoidal), one for each input, to display Lissajous figures and calculate the phase difference between the signals.