Reasons and solutions for unstable oscilloscope graphics
Reasons for unstable oscilloscope graphics:
1. The signal itself is unstable.
2. The oscilloscope is not stable enough.
3. Improper selection of synchronization source or synchronization method.
4. Improper selection of trigger level.
Solution:
If the trigger conditions are incorrect, take the ZDS2022 oscilloscope as an example:
1. Select appropriate time division TIME/DIV and voltage division VOLTS/DIV
2. The trigger source Source must be selected at a stable input signal terminal. For example, if the signal is input from CH1, CH1 must be selected.
3. Adjust the horizontal level Trig Level until the Trig light near the knob lights up.
4. Mag *10 must be turned off. There are synchronization buttons or knobs on the oscilloscope. After adjusting and synchronizing with it, it will be stable.
The difference between ac and dc coupling of oscilloscopes
The coupling control determines how the input signal passes from the BNC input on the oscilloscope's front panel to the rest of the channel's vertical deflection system. Coupling control can be set in two ways, namely DC coupling and AC coupling.
1. DC coupling method
Provides a direct connection path for signals. The signal therefore provides a direct connection path. Therefore all components of the signal (AC and DC) affect the oscilloscope's waveform display.
2. AC coupling method
Connect a capacitor in series between the BNC terminal and the attenuator. In this way, the DC component of the signal is blocked, and the low-frequency AC component of the signal will also be blocked or greatly attenuated. The low-frequency cutoff frequency of the oscilloscope is the signal frequency at which the signal amplitude displayed by the oscilloscope is only 71% of its actual amplitude. The low-frequency cutoff frequency of an oscilloscope is mainly determined by the value of its input coupling capacitor. The typical low-frequency cutoff frequency of the oscilloscope is 10Hz.
3. The difference between ac and dc coupling of oscilloscopes
AC coupling will filter out the DC component, causing the average value to be zero. DC coupling is direct coupling and does not change. The low-frequency cutoff frequency of an oscilloscope is mainly determined by the value of its input coupling capacitor. The typical low-frequency cutoff frequency of the oscilloscope is 10Hz.
