Twelve tips of oscilloscope you must know
(1). The most valuable index of oscilloscope ---Bandwidth, class parameter
(2). How high is the sampling rate?
Generally speaking, the sampling rate is 5 times the bandwidth, such as 200M oscilloscope, with 1G sampling rate is ok.
The pursuit of higher sampling rate is nothing more than to catch small burrs, but these high frequency burrs have been filtered out in the bandwidth layer, and higher sampling rate cannot bring good benefits.
(3). What is the difference between normal trigger and automatic trigger?
Normal trigger, it will sample the waveform only with trigger event satisfies the condition.
Automatic trigger, after wait for a moment, if there is no eligible trigger events occur, the oscilloscope will force the trigger function and start sampling. As random trigger position, the waveform will show unsteady. If above sequence occurs, please adopt normal mode.
(4). How to catch abnormal signal under uncertain condition?
You could catch the signal with template trigger.
When the template trigger is turned on, the template actually comes as a layer. It will constantly detect whether there is waveform that will touch the area of the template. When there is waveform that touches the template, a signal will be detected and it will be filtered and displayed.
(5). Are those channels isolated of oscilloscope?
No. Bottom of oscilloscope is connected with the earth, it could not be connected directly with the zero line.
To isolation, transformer could directly measure 220V city power, however, this is not recommended, and the safest and correct method it to use difference probes.
(6). Which is more accurate between oscilloscope and multimeter when measure voltage?
The vertical resolution ratio of general oscilloscopes is 8 bits. The measure accuracy is related to vertical resolution ratio and vertical gear.
The accuracy of multimeter is much higher. ADC of six and a half meter is up to 24 bits. That of handheld meter is far more than 8 bits. The voltage measured by the multimeter is more reliable.
(7). Differences between probe X1 and gear X10?
Two important points
Different attenuate bandwidth, signal x1 gear amplitude does not decay. X10 gear signal decay to 1/10 of original signal.
Different bandwidth, bandwidth of X1 gear is almost 10M, and 250M for X10 gear.
(8). Does the general oscilloscope probe need to be calibrated periodically?
The standard does not have a specific metering specification for the probe, but for passive probes, at least the probe compensation must be adjusted when the probe is replaced and the probe switches channels.
(9). What is main factor determines the price of oscilloscope probe ?
The main determinants of price are, of course, bandwidth and functionality.
There are many types of oscilloscope probe, different performance, such as high voltage, difference, active high-speed probe and so on, the price also from a few hundred yuan to nearly ten thousand dollars.
The probe is part of the oscilloscope contact circuit. A good probe can provide the fidelity required for testing.To do this, even passive probes must have a very large number of passive device compensation circuits (RC networks) inside.
(10). Is there any way to measure the working condition of high frequency transformer or inductor core by oscilloscope?
Can rely on the oscilloscope's own power analysis software to do, there is a function - B-H curve analysis, it can reflect the working state of the magnetic core, but also can measure the dynamic inductance value, and get the core loss.
(11). Can an oscilloscope perform Fourier decomposition?
Modern digital oscilloscope mostly has FFT function, but need to pay attention to FFT can analyze the number of points, which directly determines the accuracy of FFT analysis results, avoid spectrum leakage.
(12). Can oscilloscope filter? Such as low pass filtering of PWM wave?
Oscilloscopes typically have a 20MHz bandwidth limit, and this is a hardware filter.Some oscilloscopes also support software filters with adjustable cutoff frequencies.
How to use digital oscilloscope to distinguish analog bandwidth from digital real - time bandwidth？
Bandwidth is one vital index of oscilloscope. Bandwidth of analog oscilloscope is one certain value, however, bandwidth of digital oscilloscope has two kinds, analog bandwidth and digital real-time bandwidth. Digital oscilloscope to repeating the signal in a sequential sampling and random sampling technology can achieve the maximum bandwidth of the oscilloscope digital real-time bandwidth, real-time digital bandwidth and the highest frequency and digital waveform reconstruction technology related factor K = (digital real-time bandwidth digital highest rate/K), generally not directly given as an indicator. It can be seen from the definition of the two kinds of bandwidths that the analog bandwidths are only suitable for the measurement of repeated periodic signals, while the digital real-time bandwidths are suitable for the measurement of repeated signals and single signals at the same time.
The manufacturer claims the bandwidth of oscilloscope can achieve how many megabytes, it is analog bandwidth actually, digital real time bandwidth is below this value. For example, if the bandwidth of an oscilloscope is 500MHz, it actually means that its analog bandwidth is 500MHz, while the highest digital real-time bandwidth can only reach 400MHz, which is much lower than the analog bandwidth. Therefore, when measuring a single signal, it is necessary to refer to the digital real-time bandwidth of the digital oscilloscope, otherwise it will bring unexpected errors to the measurement.
The development of oscilloscope probe
In the past 50 years, the interface design of various oscilloscope probes has been evolving continuously to meet the requirements of increased instrument bandwidth speed and measurement performance. In the earliest days, banana plugs and UHF connectors were commonly used. In the 1960s, the common BNC connector became the common probe interface type because BNC was smaller and more frequent. Currently, the BNC probe interface is still used for test and measurement instrument design, and the current higher quality BNC connector provides a maximum available bandwidth function of nearly 4GHz.
Later, some manufacturers put forward the common workarounds, BNC type probe interface design in the use of the BNC connector at the same time, additional provides a simulation code detection scale coefficients of stitching, as part of the mechanical and electrical interface design, which makes the oscilloscope is compatible with automatic detection and change the oscilloscope display of vertical attenuation range.
Requirements for oscilloscope current probe
Wide frequency range: from dc to tens or even hundreds of megabytes.
The range is large: from milliampere to kiloampere.
Small size: with the improvement of integration and the increase of signal frequency, the external size of components is getting smaller and shorter and pins are getting shorter and shorter.
Easy operation and high accuracy.