It, in effect, gives the electronic engineer an eye to ‘see’ what is happening inside the circuit itself. It is only by ‘seeing’ the signal wave forms that he/she can correct errors, understand mistakes in the circuit design and thus make suitable adjustments.
An oscilloscope can display and also measure many electrical quantities like ac/dc voltage, time, phase relationships, frequency and a wide range of waveform characteristics like rise-time, fall-time and overshoot etc. Non-electrical quantities like pressure, strain, temperature and acceleration etc. can also be measured by using different transducers to first convert them into an equivalent voltage.
 |
| figure 1 |
As seen from the block diagram of an oscilloscope (Figure 1), it consists of the following major sub-systems:
1. Cathode Ray Tube (CRT): it displays the quantity being measured.
2. VERTICAL AMPLIFIER: it amplifies the signal waveform to be viewed.
3. HORIZONTAL AMPLIFIER: it is fed with a saw-tooth voltage which is then applied to the X-plates.
4. SWEEP GENERATOR: produces saw-tooth voltage waveform used for horizontal deflection of the electron beam.
5. TRIGGER CIRCUIT: produces trigger pulses to start horizontal sweep.
The operating controls of a basic oscilloscope are shown in Figure 2. The different terminals provide.
1. Horizontal amplifier input,
2. Vertical amplifier input,
3. Sync. input,
4. Z-axis input,
5. External sweep input.
As seen, different controls permit adjustment of
1. INTENSITY: for correct brightness of the trace on the screen,
2. FOCUS: for sharp focus of the trace.
3. HORIZONTAL CENTERING: for moving the pattern right and left on the screen.
4. VERTICAL CENTERING: for moving the pattern up and down on the screen.
5. HORIZONTAL GAIN (also Time/div or Time/cm): for adjusting pattern width.
6. VERTICAL GAIN (also volt/div or volt/cm): for adjusting pattern height.
7. SWEEP FREQUENCY: for selecting number of cycles in the pattern.
8. SYNC. VOLTAGE AMPLITUDE: for locking the pattern.
The different switches permit selection of:
 |
| Figure 2 |
