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FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
pantelei4:
--- Quote from: radiolistener on August 22, 2019, 09:02:26 am ---With Hi-Z your oscilloscope will show you random amplitude, you cannot believe it.
--- End quote ---
Do not invent, everything is correct, it shows without a terminator.
radiolistener:
--- Quote from: pantelei4 on August 22, 2019, 09:07:50 am ---With Hi-Z your oscilloscope Do not invent, everything is correct, it shows without a terminator.
--- End quote ---
No. With no terminator, there is 1M +15pF impedance on the cable end.
It means that your cable works as impedance transformer with random transformation ratio. In simple words, your 1 meter cable works as step-up or step-down transformer with random and unknown transformation ratio.
Since we-re talking about 100 ns steps, you're needs to take into account 10 MHz bandwidth. But since each step has square waveform, actual signal bandwidth is much more higher than 10 MHz. It's about 100-1000 MHz.
So, you can assume unterminated measurement just as random value... You cannot believe amplitude measurement at the end of transmission line with no proper termination.
pantelei4:
--- Quote from: radiolistener on August 22, 2019, 09:15:55 am ---No. With no terminator, there is 1M +15pF impedance on the cable end.
Since we-re talking about 100 ns steps, you're needs to use 10 MHz frequency.
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I can set a time step longer if I use a low frequency and it will not change anything.
In addition, the inclusion of a 20 MHz bandwidth limit also does not spoil the signal, just steps with a longer front, but they can also be seen with the same vertical step.
radiolistener:
pantelei4, since there is no proper impedance match, this is measurement at the output of transformer with random transformation ratio and random frequency response. It's transformation ratio will depends on many factors, include cable length and frequency.
All what you know, is that all amplitudes on your oscilloscope will be scaled with random factor which also depends on the frequency. So, there is no way to measure amplitude in correct way with no proper termination at the end of transmission line.
pantelei4:
--- Quote from: radiolistener on August 22, 2019, 09:27:28 am --- since there is no proper impedance match, this is measurement at the output of transformer with random transformation ratio and random frequency response. It's transformation ratio will depends on many factors, include cable length and frequency.
--- End quote ---
The level of quantization will not change.
Can show you the vertical step of a linearly increasing signal with a frequency of 1 Hz? |O
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