What are the time base calibration methods for digital oscilloscopes?

A digital oscilloscope is a time domain electronic measuring instrument. In addition to displaying waveforms, it can also be used to measure various waveform parameters, such as signal rise time, time interval, frequency, amplitude, etc. It also has powerful data processing functions, and some even have FFr analysis functions, which can analyze signals from the frequency domain. When calibrating a digital oscilloscope, the time base is a must-check item. So what are the methods for calibrating the time base of digital oscilloscopes?

Digital oscilloscope time base calibration method

1. When the digital oscilloscope has a time delay function

Select a time stamp signal with a period of 10ms (or 1ms 100m®, adjust the settings of the digital oscilloscope so that the waveform is displayed stably and centered on the screen, and within the selected delay time, select the fastest horizontal scan speed. Adjust the waveform so that the rising part The mark point is centered horizontally, leaving the horizontal and vertical positions unchanged.

2. When the digital oscilloscope has no time delay (deIay) function

Some digital oscilloscopes have neither time delay function nor clock output port. The error can be detected by using the time base amplification method. Taking calibration as an example, if a time scale with a time interval of lms is input, the signal is not viewed in a file during calibration, but in a scanning file. At this time, the time scanning accuracy is amplified by 1000 times, which can be observed by the human eye. .

Calibration method: First, align the first time scale pulse with the horizontal scale center line of the oscilloscope in the lus scan file, and then adjust the displacement to move the time scale forward until the -+ pulse appears on the screen. At this time, the oscilloscope measures The percentage of the deviation between the time interval and the input time scale signal divided by 1ms is b%.

3. Set the frequency of the synthetic signal generator to 10MHz, adjust the output amplitude of the synthetic signal generator to cover about 80% of the screen range, and adjust various settings of the digital oscilloscope so that the waveform is displayed stably and centered on the screen. Reduce the horizontal deflection coefficient of the digital oscilloscope and put it in undersampling mode until an aliased periodic waveform of about the outer period is observed on the screen. Turn on the automatic measurement function of the digital oscilloscope and select the frequency measurement function to read the beat waveform frequency of the input signal and sampling clock on the screen. Indicates the beat waveform frequency HZ measured by the oscilloscope.

4. For digital oscilloscopes with time-base clock output, you can directly connect the frequency meter to the time-base clock output of the digital oscilloscope, read and record the frequency value displayed by the frequency meter, the relative error, ∞ is the time-base clock measured by the frequency meter Frequency Hz.