Getting Started with Oscilloscopes
Oscilloscope is an essential instrument in modern appliance repair. With it technicians will be able to quickly and accurately find the fault, so the correct and skilled use of oscilloscopes is a mandatory course for home appliance repairers.
Although the oscilloscope brand, model, variety, but its basic composition and function is similar, this article introduces the use of general-purpose oscilloscope.
Panel introduction
1. Brightness and focus knob
Brightness knob is used to adjust the brightness of the light trace (some oscilloscopes called glow), the use of the brightness should be appropriate, if too bright, easy to damage the oscilloscope tube. Focus knob is used to adjust the degree of focus (thickness) of the light trace, when used to make the graphics clear.
2. Signal input channel
Commonly used oscilloscopes are mostly dual-trace oscilloscopes, there are two input channels, respectively, channel 1 (ch1) and channel 2 (ch2), respectively, can be connected to the oscilloscope probe, and then the oscilloscope shell ground, the probe inserted into the part to be measured for measurement.
3. Channel selection keys (vertical mode selection)
There are five channel selection keys for commonly used oscilloscopes:
(1) ch1: Channel 1 is displayed separately;
(2) ch2: channel 2 is displayed separately;
(3) alt: two channels are displayed alternately;
(4) chop: two-channel intermittent display, for scanning slower dual-trace display;
(5) add: the signal of two channels is superimposed. Maintenance to choose channel 1 or channel 2 for more.
4. Vertical sensitivity adjustment knob
To adjust the vertical deflection sensitivity, the position of the knob should be adjusted according to the amplitude of the input signal, and the value indicated by the knob (e.g., 0.5v/div, which means that the amplitude of each frame in the vertical direction is 0.5v) should be multiplied by the number of frames taken up by the measured signal in the vertical direction of the screen, which is the amplitude of the measured signal.
5.Vertical Shift Adjustment Knob
It is used to adjust the position of the measured signal trace in the vertical direction of the screen.
6. Horizontal Scanning Adjustment Knob
To adjust the horizontal speed, the position of the knob should be adjusted according to the frequency of the input signal, and the value indicated by the knob (e.g., 0.5ms/div, which means that the time of each frame in the horizontal direction is 0.5ms) should be multiplied by the number of occupied frames of the measured signal in a cycle, that is to say, it will arrive at the period of the signal, and it can also be converted into the frequency.
7. Horizontal position adjustment knob
It is used to adjust the position of the measured signal light trace in the horizontal direction of the screen.
8. Trigger mode selection
Oscilloscopes usually have four trigger methods:
(1) Normal (norm): when there is no signal, no display on the screen; when there is a signal, with the level control with the display of stable waveforms;
(2) automatic (auto): when there is no signal, the screen displays a light trace; when there is a signal, the level control is used to display a stable waveform;
(3) TV field (tv): used to display TV field signals;
(4) Peak auto (p-p auto): when there is no signal, the light trace is displayed on the screen; when there is a signal, a stable waveform can be obtained without adjusting the level. This method is only used in some oscilloscopes (e.g. caltek ca8000 series oscilloscopes).
9. Trigger source selection
There are two types of oscilloscope trigger sources: internal trigger source and external trigger source. If you choose an external trigger source, then the trigger signal should be input from the external trigger source input, which is rarely used in home appliance repair. If you select the internal trigger source, generally select channel 1 (ch1) or channel 2 (ch2), should be selected according to the input signal channel, if the input signal channel is selected as channel 1, then the internal trigger source should also be selected channel 1.
