Digital oscilloscopes is triggered by waveform display, measuring, storage and data processing, etc, waveform, the unique advantages growing popularity. As a result of digital oscilloscopes and analogue oscilloscope between larger difference, if use undeserved, can produce bigger, thereby affecting the measurement error test tasks.

Distinguish real-time digital simulation bandwidth and bandwidth Bandwidth is one of the most important indicators oscilloscope. The bandwidth is an analogue oscilloscope fixed value, while the bandwidth of the digital oscilloscopes are simulated bandwidth and digital real-time bandwidth. Digital oscilloscopes by order of repeated signal sampling or random sampling technique can achieve the highest bandwidth for real-time digital oscilloscopes, bandwidth digital real-time bandwidth with highest frequency and digital waveform reconstruction technique factor K related (= the highest number of real-time bandwidth digital speed/K), generally not as an index directly. From the definition of two kinds of bandwidth can be seen only suitable for simulating bandwidth, repeated measurements of periodic signal, and is also suitable for real-time bandwidth digital signal and repeated measurements of single signal. It says the bandwidth of the oscilloscope, how can actually refers to the simulation, real-time bandwidth digital bandwidth is less than the value. For example TES520B TEK company of bandwidth for 500MHz, actually refers to the simulation, and 500MHz bandwidth for the highest number 400MHz achieve real-time bandwidth only than analog bandwidth. So in a single signal, the number of real-time reference digital oscilloscopes, otherwise, it will give bandwidth measurement bring unexpected errors.

Relevant sampling rate Sampling rate is also called digital rate, refers to the unit of time, the analog input signal sampling frequency, often with MS/s. Sampling rate of digital oscilloscopes is an important index.

1 if the sampling rate, easy enough to mix superposition phenomenon appears If the input signal for oscilloscope sinusoidal signal, a 100 KHZ oscilloscope display of the signal frequency 50KHz, is this what is the row? This is the sampling oscilloscope, slow rate of mixed stack phenomenon. Mixed stack is oscilloscope displayed on the screen of the signal frequency waveforms than actual frequency, or even oscilloscope trigger indicator light, but that has been the waveform is still unstable. Mix the produce is shown in figure 1. So, for an unknown frequency waveforms, how to determine whether the waveform display is mixed stack? Can sweep through slowly changing quickly to rapidly t/div when the yankees gear, see whether frequency waveforms sharp change, if the parameter is mixed, waveform composite has occurred, The waveform in a shaking or when the yankees files quickly and stabilize mixed composite wave has occurred. According to the specific reason suggests, sampling dc power supply rate at least above of high signal twice won't occur, such as a 500MHz mixed signals, need at least 1GS/s sampling rate. There are several ways you can simply to prevent mixed stack:

Saul, adjusting speed, Robert adopts automatic Settings (Autoset), Try to collect way, switch to the envelope or peak detection means, because the envelope is collected in more extreme records, and peak detection in single mode is collected in the record for minimum and maximum values, the two methods can be detected rapidly changing signal. Robert has Insta Vu collection if oscilloscope, can choose, because this acquisition waveform speed, using this method is similar to that of the waveform in analogue oscilloscope display of the waveform.

2 sampling rate and t/div

Each of the biggest sampling rate of digital oscilloscopes is a fixed value. However, in an arbitrary scanning time t/div, sampling rate is under the type of fs: Fs = N/N (t/div) for each sampling points When sampling points for certain value, N t/div 0.2%fs and inversely proportional to Saul, sampling speed, lower rate. Below is a group of Saul TDS520B sampling rate with the data: Table 1 sweep speed and sampling rate T/div (ns) 1252550100200fs (GS/s 502510210.50.25) To sum up, the use of digital oscilloscopes, in order to avoid mixed stack, sweep speed files in the best position and fast speed. If you want to capture of evanescent burr, sweep speed files are the best in the position of Saul slower speed. Digital oscilloscopes dc power supply rise time In analogue oscilloscope, the rise time is an extremely important oscilloscope. While in digital oscilloscopes, rise time don't even as indicators are clear. Because of the measurement method for digital oscilloscopes, automatic measurement of time not only with the rising of the relative position of sampling points, as shown in figure 2 in a rise in the said just two points, then rise time intervals for digital of 0.8 times. Figure 2 in the rise of the central along a sampling point, then the same wave, rise time intervals for the digital 1.6 times. In addition, rise time and esau speed, the same below TDS520B measurement is a group of esau when wave velocity and the rise of the time data:

Table 2 sweep speed and rise-time t/div (ms) 502010521tr (s) 800320160803216 speeds By this group of data can be seen on the rise time, although the waveform is a fixed value, and use of digital oscilloscopes measurement results for sweep speed oscilloscope can differ greatly. The rise time of analogue oscilloscope and speed, and with the rise time of digital oscilloscopes and sweep speed, position of sampling, using digital oscilloscopes, we cannot use analogue oscilloscope, according to the measure of time to launch the rise time signal.