How to use digital oscilloscopes and frequently asked questions
How to use an oscilloscope
1. Obtain the baseline: When the operator uses an oscilloscope without an instruction manual, he must first obtain the finest horizontal baseline before using the probe to perform other measurements. The specific methods are as follows: (1) Preset the switches and knobs on the panel. Set the brightness to moderate, the focus and auxiliary focus to moderate, the vertical input coupling to "AC,," the vertical voltage range selection to "5mv/div", the vertical working mode selection to "CHl", the vertical sensitivity fine-tuning calibration position to "CAL", The vertical 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 "0.5ms/div", the A scan time fine adjustment is set to the calibration position "CAL'', and the horizontal position is set to the middle position. , the scanning working mode is set to "A", the trigger synchronization mode is set to "AUTO", the slope switch is set to "+", the trigger coupling switch is set to "AC'', and the trigger source selection is set to "INT". (2) Press the power switch. The indicator light is on. (3) Adjust the relevant control knobs such as A brightness focus to produce a thin and bright scanning baseline. Adjust the baseline so that its position in the middle of the screen basically coincides with the horizontal coordinate scale. (4) Adjust the trajectory parallelism control to make the baseline Parallel to the horizontal coordinate.
2. Display signal: Under normal circumstances, the oscilloscope itself has a 0.5Vp-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. The range and sweep time factor knobs, the amplitude and width of the square wave should change. This means that the oscilloscope has been basically adjusted and can be put into use.
3. Measure the signal: Connect the test line to the CHl 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 usage methods 1. AC peak voltage measurement (1) Obtain baseline. (2) Adjust the V/div knob so that the waveform displays 5div (i.e. 5 grids) in the vertical direction. (3) Adjust "A trigger level" to obtain stable display. (4) Calculate the peak voltage using the following formula. Voltage (p-p): vertical deflection amplitude/degree x (VOLTS/div)/switch gear pole x probe 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, and the x10 probe attenuation magnification is used, and the data is substituted: Voltage 2 5. 6X0.5X10228V. 2. Rise time measurement Rise time: horizontal distance (degree) x time/degree (gear)/expansion coefficient. For example: the distance between two points of the waveform is 5 degrees, the time/degree level is 1Us, x10 expansion is not expanded (i.e. x1), the given value is replaced by: rising time I division; 5X1 / 1; 51xs. 3. Phase difference measurement Phase difference: horizontal difference value (degree) x horizontal scale calibration value (degree/degree). For example: the horizontal difference is 0.6 degrees, and each degree is calibrated to 45 degrees. Substitute the given value into the formula: phase difference: 0.6x45:27
1. How to measure DC voltage?
Answer: First, you need to set the coupling mode to DC, adjust the vertical gear to an appropriate value according to the approximate range, and then compare the displacement of the offset line and the channel mark.
2. Users reported that the amplitude exceeds the screen range when measuring 220V mains power? How to measure the phase difference of three-phase power supply?
Answer: The maximum input peak-to-peak voltage is 400V. According to the effective value conversion peak-to-peak formula, the 220V mains power exceeds 400V peak-to-peak voltage, and the amplitude exceeds the normal range of the screen. When using an oscilloscope to measure the phase shift of a three-phase power supply, you can set the trigger source to the mains, use one channel to measure the A-B waveform first, then store it as a reference waveform, and then use a probe to connect B-C. At this time, the phase shift can be measured.
3. What is confusion suppression?
Answer: Confusion is a condition caused by the frequency collected by the oscilloscope being lower than twice the maximum frequency of the actual signal. Confusion suppression is specially designed to prevent the occurrence of confusion. Confusion suppression can identify the maximum frequency of the signal and collect the signal at 2 times the maximum frequency.
