Use of digital oscilloscopes

refer to the use of a digital oscilloscope ppt 2015-11-22 21:45:42

Note the following points when using:

1, set the input signal coupling mode , generally there are 3 kinds of coupling mode, AC (AC coupling), DC (DC coupling), GND (ground). As the first part of the oscilloscope structure (red box on the left)

The actual output waveform corresponding to the selection of three coupling modes is posted below

2, some parameters of the oscilloscope, including: bandwidth, sampling rate, storage length, etc.

Bandwidth: Bandwidth is one of the important indicators of the oscilloscope, and the amplifier bandwidth definition is the same, that is, the so-called -3db Point, in the oscilloscope input sine wave signal, amplitude attenuation to the original signal amplitude of 0.707 times times the frequency point, called the oscilloscope bandwidth. That is, if an oscilloscope bandwidth of 100MHz, using it to test a frequency of 100MHz, amplitude of 1Vpp signal, the last measured signal amplitude of only 100mhz,0.707vpp. (This understanding compares the image actual)

For oscilloscope bandwidth selection, there is an application article can refer to the following: http://jingyan.baidu.com/article/1709ad80b290f74634c4f0c9.html

Bandwidth Selection Essentials: For digital applications, the oscilloscope bandwidth should be at least 5 times times faster than the fastest clock rate for the design being measured. However, in order to accurately measure the edge speed of the signal, the oscilloscope bandwidth is determined based on the maximum actual frequency component of the signal. For analog applications, the oscilloscope bandwidth should be at least 3 times times higher than the maximum frequency of the analog signal in the design being measured.

sampling rate: The inverse of the sampling point time interval, that is, the higher the sampling rate, the more points are sampled in unit time, the more realistic the waveform.

Storage length (storage depth): storage length = sample rate X Sample time

3, the trigger source selection

(1) A single test, the trigger source must be the same channel as the measured signal, for example, Y-channel CH1 test trigger source must be selected CH1, otherwise the waveform will be unstable

(2) Two of the same-frequency signal dual-channel test, the signal should be selected to be strong all the way to trigger the signal source.

(3) Two signals with an integer multiple frequency relationship should be selected as the trigger signal source with low frequency.

Use of digital oscilloscopes