Introduction to the Oscilloscope's Auto-Setup and Auto-Range

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Introduction to the Oscilloscope's Auto-Setup and Auto-Range [Copy link]

The automatic function of an oscilloscope mainly refers to the automatic setting and automatic range of the oscilloscope. Please note that it is not the same as the automatic trigger in the trigger, so don't confuse them. Some people who are very skilled in using oscilloscopes may say that the automatic function is only suitable for oscilloscope novices and they never use it. It is true that all the effects of the automatic function of the oscilloscope can be achieved by manually adjusting the oscilloscope, so it will not have any impact if people who are skilled in using oscilloscopes never use the automatic function. In addition, because some old models of oscilloscopes may take several seconds to automatically adjust, it may not be as fast as adjusting it by yourself. However, if our oscilloscope responds quickly automatically, then mastering the automatic function can greatly help us improve the efficiency of using the oscilloscope. The automatic function is not only for oscilloscope novices. People who are skilled in using oscilloscopes can use the automatic function in appropriate scenarios to achieve twice the result with half the effort.

Next we will discuss the automatic functions of the oscilloscope in detail in two parts: automatic setup and automatic ranging.

auto configuration:

When we connect a signal to the oscilloscope, the waveforms we see may be of various types. The waveforms shown in the figure below are actually the same square wave signal. Due to the different settings of the waveform in the horizontal direction (time base) and the vertical direction (vertical scale), they appear to be in different types.

At this time, we click the "auto" button on the oscilloscope, and the oscilloscope can quickly adjust the time base and vertical scale so that the waveform display is suitable for our observation.

This process usually takes less than one second. Of course, people who are skilled in using oscilloscopes can also adjust the signal quickly, but the speed is generally not as fast as the automatic one. Many oscilloscope veterans think that the automatic mode is unnecessary, mainly because many old-fashioned oscilloscopes have very slow automatic modes, but today's digital oscilloscopes have very fast automatic modes.

In addition, we open the automatic setting function menu of the oscilloscope. We can see that the oscilloscope can also automatically open the channel according to the set threshold level. For example, if the threshold level is currently set to 10mV, after the automatic opening of the channel is turned on, the channel will be automatically opened when the maximum signal value of any channel exceeds 10mV, and the channel will be automatically closed when the maximum signal value of any channel is less than 10mV.

There is an automatic trigger source below the automatically opened channel. If you don't know much about oscilloscope triggering, you can learn about it first. When the oscilloscope is triggered, there must be an object. If the automatic trigger source is set to the maximum signal, then the trigger source will switch to the channel with the largest voltage signal.

As shown in the figure below, the current trigger source is channel 2, and the voltage of channel 2 is about 1mV. The current automatic setting is a threshold level of 10mV, the channel is automatically turned on, and the automatic trigger source is the maximum signal. Therefore, when AUTO is turned on, the oscilloscope automatically switches the trigger source to channel 1, closes channel 2, and then adjusts the waveform of channel 1 to the appropriate size. The whole process only takes one second. It can be seen that the flexible use of the oscilloscope's automatic settings is not exclusive to oscilloscope novices, but also of great help to oscilloscope experts.

One thing to note here is that the frequency of the measured signal under automatic setting should be no less than 20Hz, the duty cycle should be greater than 1%, and the amplitude should be at least 2mVpp. If it exceeds this parameter range, the automatic setting will fail. This is actually affected by the automatic triggering. When the trigger is in automatic mode, if the oscilloscope cannot be triggered within a certain period of time, the oscilloscope will randomly capture and display the waveform. Therefore, one cycle of the signal must be within the time range of the oscilloscope waiting for automatic triggering, otherwise

Even if you press AUTO, the signal cannot be adjusted automatically.

Autoranging:

After understanding the automatic settings of the oscilloscope, it is very easy to understand the automatic range. When the oscilloscope measures a signal, the amplitude and frequency of the signal are often stable, which is one of the reasons why the waveform can look stable. However, if the amplitude and frequency of the signal are constantly changing, how can we quickly adjust the oscilloscope to make the waveform displayed on the screen the right size? The automatic range can help us solve this problem. No matter how the waveform changes, there is no need to press the AUTO button after turning on the automatic range. The oscilloscope can quickly adjust the size of the signal on the screen for each waveform change, so that it is always in the right position. This is very useful for analyzing dynamically changing waveforms or when you can't free your hands to press AUTO.

Let’s look at the auto-range settings. The auto-range can also set the vertical scale (ordinate), horizontal time base (abscissa) and trigger level individually.

It should be noted that the auto-range function and the auto-set function cannot coexist. When the auto-range function is turned on, the auto-set function will become invalid.