IDSO1070 Sample rate

amy

Customer Consultation

Hello!
I bought iDSO1070A oscilloscope from your store https://www.aliexpress.com/item/33000749687.html?spm=a2g0s.9042311.0.0.17d733eduyJcr4, all delivered well...

But when I started working with him, questions immediately arose:
1)  According to the documentation, Real-time Sampling Rate: 250MSa / s (single channel), 125MSa / s (two channels), but the application (IDSO1070A Software ver 1.0.22) displays 200MSa / s (single channel), the screenshot is attached below.
2) In the screenshot, the frequency of the measured signal is 36 MHz, TTL levels, it is not clear where such distortions come from.

Please tell me what is the problem, it may be necessary to update the firmware, it is very important for me that the oscilloscope can measure the frequency of 70 MHz.

I need to understand whether to open a dispute or not.


Best wishes

amy

Reply

The software shows an error. The maximum sampling rate is 250MSa/s for single channel.
To test the 36MHz signal, do you use a 50 ohm impedance matcher?
In addition, 36MHz square wave is different from 36MHz sine wave, which is composed of sine waves of different frequencies and higher frequencies.
If you want to test a square wave, it is recommended to choose an oscilloscope with a bandwidth greater than 10 times the frequency of the square wave.

amy

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Because the square waveform contains many high frequency harmonics. For example, a 50MHz square waveform, according to the Fourier expansion, contains 50MHz, 150MHz, 250MHz, 350MHz, 450MHz, ... 50×(n+1)MHz harmonics (all sine waveform) components. If you use a low-bandwidth oscilloscope, the high-frequency harmonic components will be attenuated when passing through the oscilloscope. For example, a 50MHz oscilloscope can only leave a 50MHz fundamental wave, so the result displayed by the oscilloscope is a sine waveform. Therefore, it is generally believed that to observe a square waveform, you need to see the fifth harmonic of the square waveform, that is, the 9th harmonic. Therefore, an oscilloscope with a bandwidth of more than 9 times the square waveform frequency is needed.