Hi,
You may have already done this, but if you log the same pulses with a
counter or actual TDC IC you can view it and see how they compare with
your measurements.
Then you can look at how to get them closer - or find that it's
actually correct and that's just where the pulse is at the time.
In message <59ab451c-ca1b-4824-a953-4f0f28b66...@kfu.com>, Nick Sayer via
time-nuts writes:
>My theory at the moment is that sampling the ADC multiple times in a row might
>help, but then what’s the best way to (quickly) pick which sample to use?
If you are sampling for noise: Always
I always try to calculate things like the standard deviation and
peak-to-peak to get some idea if the measurement is valid.
A DSO with infinite persistence or envelope mode is great for tracking
this sort of thing down during development. Only toy DSOs will lack
both.
On Wed, 05 Oct 2016
time-nuts@febo.com said:
> Thatâs kind of why Iâm going down the road of multiple samples - to see if
> thereâs anything to it.
I would hack up some way to grab a clump (say 10) of samples and print them
out where you can capture them on a PC and analyze them.
I'd start by looking with
On Wed, Oct 5, 2016 at 7:45 PM, Nick Sayer via time-nuts wrote:
> I notice periodically that the phase measurements seem “noisy.” You can
> see that over the course of several seconds the value doesn’t change, then
> it jumps a bunch and then comes right back.
>
Hi Nick,
It sounds like once in awhile your sampling something else too. Ground
bounce of a 10 MHz buffer, or something coupling onto your phase detector,
or running your adc at the edge of a timing spec?
How large would the outlier be in mV?
On Wednesday, 5 October 2016, Nick Sayer via time-nuts
Hi
If you are looking at a high impedance source with a “normal” ADC, you need a
buffer amp.
If you have a signal that decays, it is generally not a good idea to toss all
the samples into a
single bucket. You probably need to do some sort of slope estimation.
The still better solution is
> On Oct 5, 2016, at 5:00 PM, Bob Camp wrote:
>
> Hi
>
> What does the signal you are sampling look like?
The last time I actually looked (it was a while ago), it looked reasonable as
closely as I could look, but the ADC resolution is something like 1mV per LSB,
and I’m not
2016 6:57 PM
Subject: Re: [time-nuts] ADC sample voting algorithm?
> On Oct 5, 2016, at 4:52 PM, Bob Stewart <b...@evoria.net> wrote:
>
> Hi Nick,
>
> Are you applying sawtooth correction to your phase measurement?
Yes, these are post-correction observations. I have som
Hi
What does the signal you are sampling look like?
Does it (maybe) have a bit of noise on it?
If it is the output of a “normal” TDC, then the answer is to sample once.
Bob
> On Oct 5, 2016, at 7:45 PM, Nick Sayer via time-nuts
> wrote:
>
> This is tangentially on
quency measurement <time-nuts@febo.com>
Sent: Wednesday, October 5, 2016 6:45 PM
Subject: [time-nuts] ADC sample voting algorithm?
This is tangentially on topic, I suppose. It’s for my GPSDO.
I notice periodically that the phase measurements seem “noisy.” You can see
that over the cours
Sayer via time-nuts <time-nuts@febo.com>
> To: Discussion of precise time and frequency measurement <time-nuts@febo.com>
> Sent: Wednesday, October 5, 2016 6:45 PM
> Subject: [time-nuts] ADC sample voting algorithm?
>
> This is tangentially on topic, I suppose. It’s for my
This is tangentially on topic, I suppose. It’s for my GPSDO.
I notice periodically that the phase measurements seem “noisy.” You can see
that over the course of several seconds the value doesn’t change, then it jumps
a bunch and then comes right back.
My theory at the moment is that sampling
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