Richard H. wrote:
wrote:
I've been trying not to get into the details, because details lead to
the request for more details, and this is just way to complex to get
into here.
Darren,
You are correct that it takes details to provide a useful answer. Based
on the broad question originally asked, the URL I provided should have
met your needs. Perhaps if we understood why you didn't find what you
needed there, more accurate responses might be possible.
If you work with engineers much, you'll appreciate that people very
often ask for the wrong thing - by challenging questionable requirements
the true specs become known, often hugely affecting the complexity
involved. Here, you are asking for a degree of accuracy that is
difficult to achieve, but you say you won't actually be using it, which
sounds flawed. (Irrespective of the event frequency in the DUT, if you
are only capturing one-second granularity, more accuracy is wasted.)
I'm not asking for the wrong thing. The requirements are only
"questionable to someone not familiar to with what I am trying to do. I
never said that I will not be using the accuracy I am searching for.
And I think it has already been established that the kind of accurate
timer I need doesn't exist(or no one here knows of one).
... the timer I am
seeking is actually inadequate for all of the experiments I want to do.
Now if this is so difficult to understand, then the more complex timer
will be near impossible to explain.
So, you're wasting everyone's time (including yours) looking for a
solution that won't meet your needs? If you really want nanosecond
accuracy, we can guide you to a solution that'd give you that, but not
if you don't ask.
Who said that I'm looking for a solution that won't meet my needs?(And
I only need 1/60th of a second acccuracy).
If you would be less defensive about the requirements and share more
about your desired goal, you might get help in meeting it - the volume
of responses here demonstrates folks' willingness to help. We don't
need you to divulge your experiment, but significant requirements would
be nice (budget, size, weight, power, connectivity, inputs, outputs,
skillset), along with some tolerance for validating the potentially
difficult specs.
All this is unecessary info for a timer with a simple read-out. There
are no other rquirements than what I stated.
All that said, have you considered the overly simple solution of
software on a PC? It may be difficult to get better than 18.2ms
resolution from the system clock, but that is very close to your stated
requirement, and an RTC clock card would be easy enough to add.
Again, I need only 1/60th of a second accuracy, and the reference point
will be from "start".
Then, use SNTP to frequently check an atomic source and factor the drift
into the local clock's readings. (Or ditch the local clock entirely and
just make an SNTP/Daytime query of an atomic clock at the time you want
a reading - the accuracy can be calc'd as good as 1/250 sec.) Plus,
this is easily extensible to integrate with an event log, rather than
using a manual process.
Of course, there's no knowing if this will meet your other unstated
requirements, so perhaps it was a waste of time to share this idea?
Yeah. I guess I'll have to look elsewhere.
Thanks.
Darren Harris
Staten Island, New York.