Do you know the bandwidth of the oscilloscope? Introduction to the advanced functions of the two oscilloscopes

“In this article, the editor will introduce the oscilloscope to help you improve your understanding of it. The main content is to explain the bandwidth of the oscilloscope and the two advanced functions of the oscilloscope.

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In this article, the editor will introduce the oscilloscope to help you improve your understanding of it. The main content is to explain the bandwidth of the oscilloscope and the two advanced functions of the oscilloscope.

1. Basic introduction of oscilloscope

First, let’s take a look at the concept of an oscilloscope. An oscilloscope is a very versatile Electronic measuring instrument. It can convert electrical signals that are invisible to the naked eye into visible images, which is convenient for people to study the changing process of various electrical phenomena. It can be said that the oscilloscope has played a role in turning the intangible into tangible. The oscilloscope uses a narrow electron beam composed of high-speed electrons to hit the phosphor-coated screen to produce a small light spot (this is the working principle of a traditional analog oscilloscope). Under the action of the measured signal, the electron beam is like the tip of a pen, which can draw the change curve of the instantaneous value of the measured signal on the screen. The oscilloscope can be used to observe the waveform curves of various signal amplitudes changing with time, and it can also be used to test various electrical quantities, such as voltage, current, frequency, phase difference, amplitude modulation, and so on.

2. Introduction to oscilloscope bandwidth

Through the above introduction, I believe that everyone has a basic understanding of the oscilloscope, so what is the bandwidth of the oscilloscope?

Oscilloscope bandwidth refers to the input of a signal with the same amplitude and varying frequency. When the reading of the oscilloscope is attenuated by 3dB than the true value, the frequency at this time is the bandwidth of the oscilloscope. In other words, the test value of the input signal at the bandwidth of the oscilloscope is -3dB, which is not the highest frequency that the oscilloscope can Display. In general, the bandwidth of the oscilloscope should be 3~5 times the highest frequency of the measured signal.

Closely related to the oscilloscope bandwidth specification is its rise time parameter. An oscilloscope with a Gaussian frequency response has a rise time of approximately 0.35/fBW as measured by the standard of 10% to 90%. The rise time specification of an oscilloscope with the most flat frequency response is generally in the range of 0.4/fBW, which varies with the steepness of the oscilloscope’s frequency roll-off characteristics. If a 20% timing error is allowed when measuring the rise time and fall time parameters, an oscilloscope with a bandwidth of 1 GHz can meet the requirements of the digital measurement application. But if the timing accuracy is required to be within 3%, it is better to use an oscilloscope with a bandwidth of 2GHz.

3. Advanced functions of oscilloscope

There are many advanced functions of the oscilloscope. I will only introduce two of the advanced functions of the oscilloscope, which are related to vertical resolution and triggering.

(1) Improve vertical resolution

Most oscilloscopes are commonly used electronic testing instruments, which are widely used in many industries. The A/D resolution is 8 bits. With different acquisition modes, the vertical resolution can be improved by calculating the average value of adjacent samples as described below. So, how much can the resolution be improved by averaging and adopting the high-resolution mode? In theory, the increase is 0.5Log2N, where N is the average number of adjacent samples.

The reality is that the storage depth of 2 bytes limits this increase. Two bytes are 16 bits. One bit is reserved as the sign bit, and the remaining 15 bits are used as the data value. The rounding error makes the 14th and 15th bits a random value, which makes the actual limit value 13 bits. Therefore, the improvement can start from about six effective bits and can be increased to about 13 bits with high oversampling.

(2) Trigger

Oscilloscope is a commonly used electronic testing instrument, which is widely used in many industries. The trigger function can be synchronized horizontal scanning at the correct point in the signal, which is indispensable for clear signal verification. The trigger controller allows you to stabilize repetitive waveforms and capture single trigger waveforms.

In high-speed debugging applications, your circuit may work for 99.999% or longer. And it is .001% of the time that will cause your system to crash or it is part of the waveform you need to analyze in more detail. Advanced triggering functions, such as AB double event triggering, window triggering, logic authentication, etc., can help isolate problems, much faster than searching millions of data samples after collection.