Oscilloscope measurement operation skills and matters needing attention

To measure a simple signal, use a DS1000 oscilloscope to observe an unknown signal in the circuit, and quickly display and measure the frequency and peak-to-peak value of the signal.
(1) quickly display the unknown signal
The method to quickly display the unknown signal is as follows:
1) Set the probe attenuation coefficient to "10X", and set the switch on the probe to "10X".
2) Connect the probe of channel 1 to the point to be measured in the circuit.
3) Press the AUTO button.
The oscilloscope will automatically set the waveform display to reach. On this basis, the user can further adjust the vertical and horizontal gears until the waveform display meets your requirements.
(2) Automatically measure the peak-to-peak value with an oscilloscope
The oscilloscope can automatically measure most displayed signals. Next, use the DS1000 oscilloscope to measure the peak-to-peak value of the signal. The specific operation method is as follows:
1) Press the MEASURE button first to display the automatic measurement menu.
2) Press the menu operation key No. 1 to select source CH1.
3) Press the No. 2 menu operation key to select the measurement type: voltage measurement.
In the "Voltage Measurement" pop-up menu, select the measurement parameter: peak-to-peak value. At this time, you can see the peak-to-peak display in the lower left corner of the screen.
(3) Automatic frequency measurement with oscilloscope
Next, use a DS1000 oscilloscope to measure the signal frequency, the specific operation method is as follows:
1) Press the No. 3 menu operation key to select the measurement type: time measurement.
2) In the "Time Measurement" pop-up menu, select the measurement parameter: Frequency.
At this time, you can see the frequency display at the bottom of the screen.
【Note】
The display of the measurement result on the screen will change due to the change of the measured signal.
Observe the delay and distortion caused by the sine wave signal passing through the circuit. Next, use a DS1000 oscilloscope to observe the delay and distortion caused by the sine wave signal passing through the circuit. First set the probe attenuation coefficient of the probe and oscilloscope channel to "10X". Then connect the CH1 channel of the oscilloscope to the input end of the circuit signal, and connect the CH2 channel to the output end.
1. Display the signal of CH1 channel and CH2 channel
1) Press the AUTO button.
2) Continue to adjust the horizontal and vertical gears until the waveform display meets the test requirements.
3) Press the CH1 button to select channel 1, and turn the vertical knob in the VERTICAL area to adjust the vertical position of the channel 1 waveform.
4) Press the CH2 button to select channel 2, and adjust the vertical position of the waveform of channel 2 as before, so that the waveforms of channel 1 and channel 2 do not overlap, and it is convenient for observation and comparison.
2. Measure the delay generated after the sine wave signal passes through the circuit, and observe the change of the waveform 1) Automatically measure the channel delay, press the MEASURE button to display the automatic measurement menu.
2) Press the menu operation key No. 1 to select source CH1.
3) Press the No. 3 menu operation key to select: Time measurement.
4) Select the time measurement type: Delay 1→2.
At this time, you can see the delay value display of channel 1 and channel 2 on the rising edge in the lower left corner of the screen. The change of the waveform is shown in Figure 1-15.


Figure 1-15　 The change of the waveform after the sine wave signal passes through the circuit
Reduce the random noise on the signal If random noise is found to be superimposed on the measured signal during measurement, you can filter or reduce the noise by adjusting the oscilloscope to avoid interference to the main body signal during the measurement.

Next, use a DS1000 oscilloscope to reduce the random noise on the signal. The specific method is as follows:
1) First, set the probe attenuation coefficient of the probe and the oscilloscope channel to "10X", and set the switch on the probe to "10X".
2) Connect the signal so that the waveform is displayed stably on the oscilloscope.
3) Improve triggering by setting trigger coupling. First press the MENU button in the TRIGGER control area to display the trigger setting menu. Then select "Trigger Settings→Coupling", and then select "Low Frequency Suppression" or "High Frequency Suppression".
【Hint】
low-frequency suppression is to set a high-pass filter to filter out low-frequency signal components below 8kHz and allow high-frequency signal components to pass. High-frequency suppression is to set a low-pass filter to filter out high-frequency signal components above 150kHz (such as FM broadcast signals) and allow low-frequency signal components to pass. By setting "low frequency suppression" or "high frequency suppression", low frequency or high frequency noise can be suppressed respectively to obtain a stable trigger.
4) Reduce random noise by setting the sampling method and adjusting the waveform brightness. If random noise is superimposed on the signal under test, which causes the waveform to be too thick, the average sampling method can be used to remove the display of random noise and make the waveform thinner for observation and measurement. Random noise is reduced after averaging, and the details of the signal are easier to observe.
The specific operation method of applying the average sampling method is: press the ACQUIRE button in the MENU area of the panel to display the sampling setting menu. Press the menu operation key No. 1 to set the acquisition mode to the "average" state, and then press the menu operation key No. 2 to adjust the average times, step by step from 2 to 256 by 2 times, until the waveform display meets the requirements of observation and testing.　　　Reducing random noise can also be achieved by reducing the brightness of the waveform.
Use an oscilloscope to measure AC voltage The method of using an oscilloscope to measure AC voltage is as follows:
1) First, set the input coupling switch to the "AC" position (the expansion control switch is not pulled out), and input the AC signal from the y-axis, so that the voltage amplitude between the peak and peak of the signal waveform or between two points can be measured.
2) Read the number of cells between peaks and peaks of the waveform on the screen, and multiply it by the position of the vertical deflection factor knob to calculate the AC voltage value of the measured signal. If the expansion control switch is pulled out, divide by 5.
Precautions for using the oscilloscope When using the oscilloscope, you should pay attention to the following:
1) The amplitude of the signal under test should be estimated before the test. If it is not clear, the vertical deflection factor knob of the oscilloscope should be set to the block to avoid damage to the oscilloscope due to excessive voltage.
2) When measuring small signal waveforms, the waveform displayed on the oscilloscope is not easy to synchronize due to the weak signal under test. At this time, the following two methods can be adopted to solve the problem: Carefully adjust the trigger level knob on the oscilloscope to stabilize and synchronize the measured signal. If necessary, it can be combined with the adjustment of the sweep fine-tuning knob, but it should be noted that adjusting the knob will change the frequency reading displayed on the screen (rotate counterclockwise, the sweep factor will be enlarged by more than 2.5 times), which will cause certain difficulties in calculating the frequency. Under normal circumstances, this knob should be turned fully clockwise to make it at the calibration position (CAL). Second, use another strong signal with the same frequency (or an integer multiple) as the trigger signal of the oscilloscope. This signal can be directly input from channel 2 of the oscilloscope.
3) When the oscilloscope is working, do not place some high-power transformers around, otherwise the measured waveform will have ghosting and noise interference.
4) The oscilloscope can be used as a high internal resistance current and voltmeter. There are some high internal resistance circuits in the mobile phone circuit. If you use an ordinary multimeter to measure the voltage, the measurement result will be inaccurate due to the low internal resistance of the multimeter, and it may also affect the The test circuit is working normally, and the input impedance of the oscilloscope is much higher than that of a multimeter. Use the oscilloscope DC input mode, first ground the oscilloscope input and determine the zero baseline of the oscilloscope to easily measure the DC voltage of the signal under test.