Re: 11801 NVRAM

Albert Otten

On Mon, Sep 16, 2019 at 12:22 AM, Reginald Beardsley wrote:

FYI I created a photo album and posted a picture of the 33622A ramp displayed
on my 11801 using an SD-26 head at 1 ps/div and 2 mV/div with 1024 samples.

With a trigger signal at 100 kHz, you need a ramp at 100.0001 kHz to test the
linearity of the time base. I'm just using the internal timebase, the 33622A
set as close as I could and taking the photo at the right moment. It took a
couple of tries. I'll try for more rigorous results later.

I'd like to thank be_moulton for suggesting the idea. I had pondered the
subject, but lacked the insight needed. It's a great pleasure to have such
excellent company join us.

Have Fun!
Hi Reg,

I try to understand what's going on but don't see it. What is wrong in the following reasoning?
The trigger and ramp periods are equal to and almost equal to 10 us, with a difference of 10^-6 period or 10 ps. So per sample the time shift of ramp w.r.t. trigger is 10 ps while at 1 ps/div the time base adds only 10 fs per sample to the shift. If my view is correct then the time base accuracy plays no role in your display.
Another concern is the following. The total time shift during one trace is 10 ns, only 1/1000 period. The display shows a very small portion of the ramp. You measure at 2 mV/div. The total of 20 mV difference during one trace would correspond to 0.001 x total ramp amplitude. Hence total ramp amplitude would be 20 V, obviously way to high for the sampling head. Apart from that, the displayed ramp would nearly always be vertically off screen.

Something must be wrong in my reasoning, but what?


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