Methods for using an oscilloscope to test common circuits

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For measuring battery or DC voltage, it is first necessary to ensure that the coupling mode of the channel is set to DC. In the case of battery voltage, since it is relatively low, a probe attenuation ratio of 1X is usually sufficient; set the vertical scale to 1V or 500mV. https://pic4.zhimg.com/80/v2-67a3e77c6dd710f1eadca6203fdb2f2b_720w.jpg Make sure that the oscilloscope’s trigger mode is set to automatic. https://pic4.zhimg.com/80/v2-cd8e271aac61f401172de23bbc724f6b_720w.jpg Ensure that the battery has power or that there is a DC voltage output. Connect the probe to the positive terminal of the battery or DC supply, and connect the probe’s clip (i.e., the ground terminal) to the negative terminal of the battery or DC supply. Of course, it doesn’t matter if it’s reversed; it’s just that when the waveform is displayed, it will appear below the zero level of the oscilloscope. By turning on the oscilloscope’s function to measure the average value, the DC voltage value can be seen. https://pic4.zhimg.com/80/v2-4ebc49b1ff0c31a54d2ac789b978358b_720w.jpg As shown in the image above, we are testing a battery with a voltage of 1.6V. Note that a DC signal does not have a waveform; a straight line can be seen on the oscilloscope. Crystal oscillators are sensitive to capacitive loads. When using the ×1 setting, the probe’s capacitance is relatively high, which acts as a heavy load connected in parallel to the crystal oscillator circuit, easily causing it to stop oscillating. Therefore, it is better to use a probe with a 10X setting. We set the oscilloscope channel to AC coupling at the 10X setting. After ensuring that the crystal oscillator board is powered on, remove the cover from the probes to expose them. Connect the probe clip to the ground terminal of the motherboard, which is the negative power terminal, and have the tip of the probe make contact with one of the pins of the crystal oscillator. https://pic3.zhimg.com/80/v2-9e3552f78a6e000e3ce24a279dba130a_720w.jpg Adjust the vertical scale and time base of the oscilloscope so that at least one cycle of the waveform is displayed fully on the screen, as shown in the image below. The frequency of this crystal oscillator is 25MHz. https://pic1.zhimg.com/80/v2-0881840bb976c68d6344c88043bcd1bc_720w.jpg Additionally, the output edges of a crystal oscillator are generally quite steep, with a short rise time; since the output contains many high-frequency components, it should be treated as a high-frequency signal. The bandwidth of the probe at setting ×1 is limited, while the probe at setting ×10 operates at full bandwidth; therefore, setting ×10 must be used for measurements. The output signal of the signal generator is measured by observing the waveform it generates; generally, the output voltage is within 20V peak-to-peak. It is necessary to set the oscilloscope channel to the 1X setting, with a vertical scaling of 1V/div being sufficient. Ensure that the oscilloscope channel is set to DC coupling and the trigger mode is set to automatic. Connect the signal output port of the signal generator to the corresponding channel port of the oscilloscope to ensure that the signal generator operates properly and generates signals. Then press the AUTO button on the oscilloscope to let it automatically adjust the waveform to an appropriate position. If the automatic adjustment does not meet your requirements, you can adjust the vertical setting and the shape of the time base adjustment waveform manually. https://pic3.zhimg.com/80/v2-311890c5964b28f59d28efcf0a79388a_720w.jpg For measuring power supply ripple, it is generally recommended to use the 1X setting for the probe, in order to avoid unnecessary noise attenuation that could affect the measurement of the ripple. At the same time, remember to set the attenuation ratio of the oscilloscope channel to 1X as well. Ripple is an AC component; therefore, the \"channel coupling\" method should use AC coupling in order to restrict the input of DC signals. The ripple frequency of the output from a typical switching power supply ranges from 0 to 20 MHz. Noise caused by high-frequency synchronous switching noise and signal reflection, etc., lies in the 0–1 GHz range. Therefore, the 20MHz bandwidth limit should be enabled to filter out unnecessary high-frequency noise. https://pic2.zhimg.com/80/v2-8f1b0cde6db85fbc496df08d97a88f3d_720w.jpg To avoid interference with the signal caused by electromagnetic radiation and similar factors, the ground wire of the oscilloscope probe should be as short as possible; usually, the probe’s built-in grounding spring is used for grounding. Finally, the ripple waveform can be analyzed in the frequency domain using the FFT function, which allows for an accurate determination of the noise at each frequency point as well as the magnitude of the ripples caused by switching. https://pic2.zhimg.com/80/v2-28922cace24d39baa8fe1f342adb40cd_720w.jpg For household mains voltage of 220V (110V), disconnect the power cable of the oscilloscope and use it with batteries. Use 2 10X probes, set the channel attenuation to 10X, the vertical scale to 100V/div, and the coupling mode to AC coupling. Ensure that the device under test has an outlet for household electricity; connect the two probes to the two wires of this outlet. Then, in the oscilloscope, enable the mathematical functions and subtract the signals from the two channels – the waveform resulting from this operation is the waveform of the mains electricity. https://pic3.zhimg.com/80/v2-2f3372bda784ec0c6458f1a82b21c72e_720w.jpg Of course, the safest and most convenient way to measure the waveform of mains electricity is still by using a differential probe. For measuring and decoding signals on the automotive communication CAN H/L buses, connect Oscilloscope Channels 1 and 2 using BNC-to-banana plug cables: https://pic2.zhimg.com/80/v2-d4f9171133e678440713b3c59982380d_720w.jpg. Connect Channel 1 to PIN6 (CAN_H) of the diagnostic connector, and Channel 2 to PIN14 (CAN_L) of the same connector. Connect the ground terminals of Channels 1 and 2 to PIN4 of the diagnostic connector. Open the oscilloscope’s decoding menu to configure the CAN bus: https://pic4.zhimg.com/80/v2-a3398e90879512a8dcaa822fc80b2367_720w.jpg. Adjust the bus threshold level to obtain decoded data; set the trigger mode to decoding trigger, and adjust the vertical scale and time base to observe the signal: https://pic4.zhimg.com/80/v2-aa4413f3ab9d3b2a3e0b401fa02f079f_720w.jpg. For measuring amplifier and audio signals, set the oscilloscope’s trigger to auto mode and change the coupling type to AC. Ensure that the amplifier is powered on and generating an audio signal. Connect the probe clips and probes to the two output terminals of the amplifier, without needing to distinguish between positive and negative poles. Adjust the vertical scale so that the waveform is fully displayed on the screen. Adjusting the volume allows one to observe changes in the amplitude of the waveform. https://pic1.zhimg.com/80/v2-844bcdfe6dc251305a88f2248f5b7b7c_720w.jpg The signals from sensors in the sensor amplification circuit are usually quite weak, and it may be difficult to detect them using an oscilloscope directly. However, there is always a signal amplification section on the sensor’s motherboard; by finding the output terminal of this amplifier, it becomes possible to measure the amplified signal with an oscilloscope. Use a 1X probe, set the channel attenuation to 1X as well, use DC coupling, and set the trigger mode to automatic. Connect the probe clip to the negative terminal of the sensor motherboard power supply, and connect the probe to the output terminal of the amplifier. Set the vertical scale to 50 mv/div, and set the time base to 200 or 500 ms to enter scroll mode. The vertical setting can be adjusted appropriately based on the waveform, after which the signal received by the sensor can be observed.