How to choose the sampling rate to avoid the influence of insufficient sampling rate on test results

For an oscilloscope, bandwidth, sampling rate and memory depth are its three key indicators. If the sampling rate, which is a key indicator of an oscilloscope, is insufficient, what impact will it have on the test results?

First, let's understand what sampling and sampling rate are. In layman's terms, sampling is actually using points to depict the analog signal entering the oscilloscope. The sampling rate is the reciprocal of the time interval between two adjacent sampling points. The sampling rate is expressed in "points/second (Sa/s)". The figure below is a sampling principle diagram.

According to the Nyquist sampling principle: when sampling a sine wave, the sampling frequency must be more than twice the signal frequency to ensure that the original signal can be completely reconstructed from the sampled value. It can be seen that the oscilloscope sampling rate has a direct impact on the authenticity of the waveform construction.

The effects of low sampling rate on the waveform are as follows:

1. Waveform distortion;

2. Waveform aliasing;

3. Waveform loss;

From the above diagram, we can see that a low sampling rate will have a great impact on the test results. So how to choose the appropriate sampling rate? 1. When using the sine interpolation method, in order to accurately reproduce the signal, the oscilloscope's sampling rate must be at least 2.5 times the highest frequency component of the signal. 2. When using the linear interpolation method, the oscilloscope's sampling rate should be at least 10 times the highest frequency component of the signal. This also explains why the maximum sampling rate of an oscilloscope is usually four times or more of its rated analog bandwidth when used for real-time sampling.

The above information about the impact of insufficient oscilloscope sampling rate on test results and the selection of sampling rate is compiled and shared by Antai Test. Antai Test provides customers with integrated services ranging from solutions, product selection, instrument sales to instrument repair, instrument extended warranty, calibration, preventive maintenance and instrument training. For more questions about the use of oscilloscopes, please leave a message for communication.