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Old 10th April 2013, 06:27 PM   #1641
Salas is offline Salas  Greece
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Using AC coupling to the scope for all captures I guess. Looking early rounding in the HF. Showing the same for the grounded grid pre maybe shows a trend in the measurement loop. What is the wave generator spec? What is the probe spec and its setting?
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Old 10th April 2013, 06:33 PM   #1642
stajo is offline stajo  Sweden
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Scope is set on AC for the measures. Does that matter since its after the output cap?

Its this Very-High-Resolution Oscilloscopes from Pico Technnology one and the built in signal generator. I havent used it much so mebbe i have some settings wrong.

Probes... well, the ones that came with. It says 60 mHz on them. Setting x1

Staffan

Last edited by stajo; 10th April 2013 at 06:41 PM.
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Old 10th April 2013, 06:55 PM   #1643
Salas is offline Salas  Greece
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Oscilloscope — Vertical
Bandwidth
20 mV range
10 mV range 5 MHz
4 MHz
3 MHz
Bandwidth limiter 200 kHz, switchable
Rise time (calculated)
20 mV range
10 mV range 70 ns
88 ns
117 ns

Signal Generator
Standard output signals Sine, square, triangle, DC voltage, ramp, sinc, Gaussian, half–sine, white noise, PRBS
Standard signal frequency DC to 20 kHz

That last spec above means you should expect decent square up to 2kHz and its best rise time up to 1kHz only. Difficult to see wee HF wiggle if any is there with those rise times and bandwidths mentioned. But a low frequency one at 1kHz or under it should have been visible. AC coupling to a scope introduces further high pass but its not of interest here, avoid DC coupling in non HV CAT I capable mini scope interfaces inputs when probing valve gear. When a probe is set at X1 it drastically cuts its bandwidth spec to few MHZ but the system gains SNR is what happens. Still at much faster spec than the included generator, so its OK for that.
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Old 10th April 2013, 07:02 PM   #1644
stajo is offline stajo  Sweden
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I have a better (I think) signal generator somewhere that I might try tonight after i putted kiddo to bed. So I shall keep the other measurement settings?
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Old 10th April 2013, 07:03 PM   #1645
Salas is offline Salas  Greece
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P.S. That pico model looks good enough for audio band FFT though.
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Old 10th April 2013, 07:05 PM   #1646
Salas is offline Salas  Greece
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Quote:
Originally Posted by stajo View Post
I have a better (I think) signal generator somewhere that I might try tonight after i putted kiddo to bed. So I shall keep the other measurement settings?
If its cheap DDS it will have wiggles of its own on square waves. See if it can output 10-20kHz good squares as a loop to the scope first. Optimize any settings needed. If it can, then introduce the devices under test in the loop.
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Old 10th April 2013, 08:55 PM   #1647
stajo is offline stajo  Sweden
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You were surely right about the built in signal generators limitations up in the freq ranges. Heres some pix of that: 10kHz and 20kHz
Attached Images
File Type: png 10kHz.png (16.1 KB, 132 views)
File Type: png 20kHz.png (23.8 KB, 129 views)
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Old 10th April 2013, 08:57 PM   #1648
stajo is offline stajo  Sweden
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And heres an old Wavetek model 182 that can do the squares but with some nice wiggles
Attached Images
File Type: png 10kHzW.png (17.9 KB, 127 views)
File Type: png 15kHzW.png (19.7 KB, 126 views)
File Type: png 20kHzW.png (17.2 KB, 122 views)
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Old 10th April 2013, 08:59 PM   #1649
stajo is offline stajo  Sweden
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Heres the GG with Wavetek, 10kHz, 15kHz and 20kHz (same as above):
Attached Images
File Type: png 10kHzGG.png (17.9 KB, 23 views)
File Type: png 15kHzGG.png (16.0 KB, 20 views)
File Type: png 20kHzGG.png (17.3 KB, 20 views)
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Old 10th April 2013, 09:00 PM   #1650
stajo is offline stajo  Sweden
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And the patient itself, same freqs:
Attached Images
File Type: png 10kHz6V6.png (18.5 KB, 21 views)
File Type: png 15kHz6V6.png (17.3 KB, 18 views)
File Type: png 20kHz6V6.png (18.0 KB, 18 views)
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