How to use an oscilloscope?
(1) Obtain baseline:
When the operator uses an oscilloscope without an instruction manual, he must first obtain the thinnest horizontal baseline before using the probe to make other measurements. The specific method is as follows:
①Preset switches and knobs on the panel. Brightness is set to moderate, focus and auxiliary focus are set to moderate, vertical input coupling is set to "AC", vertical voltage range selection is set to "5 mv/div", vertical working mode selection is set to "CH1", vertical sensitivity fine-tuning calibration position is set to "CAL", vertical The channel synchronization source selection is set to the middle position, the vertical position is set to the middle position, the A and B scan time factors are preset together at "0.5 ms/div", the A scan time fine adjustment is set to the calibration position "CAL", the horizontal position is set to the middle position, and the scanning operation Set the mode to "A", the trigger synchronization mode to "AUTO", the slope switch to "+", the trigger coupling switch to "AC", and the trigger source selection to "INT".
② Press the power switch and the power indicator light will light up.
③ Adjust the control knobs related to A brightness, focus, etc., and a slender and bright scanning baseline will appear. Adjust the baseline so that its position is in the middle of the screen and basically coincides with the horizontal coordinate scale.
④Adjust the trajectory parallelism control to make the baseline parallel to the horizontal coordinates.
(2) Display signal:
Under normal circumstances, the oscilloscope itself has a 0.5 Vp-p standard square wave signal output port. After obtaining the baseline, the probe can be connected here. At this time, there should be a series of square wave signals on the screen. Adjust the voltage range and scan time. Factor knob, the amplitude and width of the square wave should change. At this point, it means that the oscilloscope has been basically adjusted and can be put into use.
(3)Measurement signal:
Connect the test lead to the CH1 or CH2 input socket, touch the test probe to the test point, and then observe the waveform on the oscilloscope. If the waveform amplitude is too large or too small, adjust the voltage range knob; if the waveform period display is not suitable, adjust the scan speed knob.
Special measurements:
(1) AC peak voltage measurement:
① Obtain the baseline.
②Adjust the V/div knob so that the waveform displays 5div (i.e. 5 grids) in the vertical direction.
③Adjust "A trigger level" to obtain stable display.
④ Use the following formula to calculate the peak voltage. Peak voltage = vertical deflection amplitude × switch block × detector attenuation magnification. For example: the measured deflection from the upper peak to the lower peak is 5.6 degrees, the VOLTS/dir switch is set to 0.5, use the ×10 probe attenuation magnification, and substitute the data into: Vp—p=5.6×0.5×10=28 V.
(2)Rise time measurement:
Rise time = horizontal distance (degree) × time/degree (stop pole)/expansion coefficient.
For example: the distance between two points of the waveform is 5 degrees, the time/degree step is 1Us, and ×10 expansion (the final expansion is ×1), substitute the given value: the rise time is 5×1/10=0.5Us.
(3) Phase difference measurement:
Phase difference = horizontal difference (degree) × horizontal scale calibration value (degree/degree).
For example: the horizontal difference is 0.6°, and each degree is calibrated to 45°. Substituting the given value into the phase difference formula is: 0.6×45=27°.
