为什么250M的6254BD测10M以上的方波根本看不出方波的样子？
测10M的波形测20M的波形
测70M的波形
您好，DDS输出方波大于20MHz以上，我们均不做定性测量。
Edited by OASJ2YSeeEhBQo1 at 2020-6-13 11:37
I can't understand Chinese language and I'm not sure how you are doing your tests, but some points you should check:
- The maximum bandwidth of ANY oscilloscope is specified to a sine wave: https://www.tek.com/support/faqs ... ined-oscilloscope-0
- What is the maximum square wave frequency that yours function generator is specified to generate? Refer to its manual. Looks like you are setting a much higher frequency than the DDS is capable of.
- For higher frequencies measurements, special care must be taken with the test setup: like type of probe, how it is attached to the instruments, length of the ground leads... all that will influence your measurement and if not done properly will induce to errors.
那这样算的话这个250M的6254BD也达不到250M啊
Edited by OASJ2YSeeEhBQo1 at 2020-6-17 09:27
Still, I am not sure what you are trying to show with the pictures above. If you are trying to test the maximum bandwidth of the oscilloscope, I have an impression that you are doing it wrong.
As you did not give any detail of the setup and procedures you are using to do the measurements, I can only suppose.
The maximum output frequency of the HT6254BD's DDS is 25MHz (according to its manual), you are trying to output 60MHz, I think that is the cause of the deformation you are seeing. Try to use a function generator capable of output the frequencies you need.
Another method, is to measure the rising time of a step pulse signal (you will need a special step signal with a very fast edge rising rate, in the order of ps. Tip: you will need a special circuit for that, try to search for "fast edge pulse generator") and then calculate the BW with that number.
Also make sure that you are using correct probes and grounding techniches.
Some articles that may be of interest:
https://community.keysight.com/c ... -bandwidth-yourself
https://community.keysight.com/c ... -of-the-scope-probe
https://community.keysight.com/c ... width-of-your-probe
OASJ2YSeeEhBQo1 replied at 2020-6-13 00:38
I can't understand Chinese language and I'm not sure how you are doing your tests, but some points y ...
yes，you are right，he shuld use sine wave test ..
the probe need calibration....
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