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Michael A. Terrell
electronics forum Guru
Joined: 24 Mar 2005
Posts: 2291
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 Posted: Fri Jul 21, 2006 1:28 am Post subject:
Re: FREQ COUNTER help
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bill.sloman@ieee.org wrote:
| Quote: |
Michael A. Terrell wrote:
bill.sloman@ieee.org wrote:
As for rattling Phil Allison's cage - the longer we keep him mad, the
better the chance that he will blow a blood vessel and lose his
capacity to manipulate a keyboard. This would be a rather pyschopathic
motivation if one considered Phil to be fully human.
The same could be said for you, Bill.
But I said it first. You have to invent your own abuse if you want to
get any brownie points.
And I don't show much sign of blowing a blood vessel.
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I don't want brownie points, Bill. Brownies are young girls on their
way to being Girls Scouts. The first sign of blowing a blood vessel is
when it explodes.
--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.
Michael A. Terrell
Central Florida |
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Michael A. Terrell
electronics forum Guru
Joined: 24 Mar 2005
Posts: 2291
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| Posted: Fri Jul 21, 2006 1:29 am Post subject:
Re: FREQ COUNTER help
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bill.sloman@ieee.org wrote:
| Quote: |
John Fields wrote:
On 19 Jul 2006 02:46:44 -0700, bill.sloman@ieee.org wrote:
As for rattling Phil Allison's cage - the longer we keep him mad, the
better the chance that he will blow a blood vessel and lose his
capacity to manipulate a keyboard. This would be a rather pyschopathic
motivation if one considered Phil to be fully human.
---
When not having to deal with some of the less-than-human lifeforms
infecting this forum, Phil often comes into his own and offers
outstanding advice, I've found. YMMV.
On his chosen subjects he is pretty good, but he does degenerate into
snarling rage remarkably quickly, and he remains incensed for
remarkably long periods.
--
Bill Sloman, Nijmegen
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Kind of like your insane anti America rants, old boy?
--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.
Michael A. Terrell
Central Florida |
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Bill Sloman
electronics forum Guru
Joined: 12 May 2005
Posts: 1080
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| Posted: Fri Jul 21, 2006 3:06 am Post subject:
Re: FREQ COUNTER help
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Michael A. Terrell wrote:
| Quote: | bill.sloman@ieee.org wrote:
Michael A. Terrell wrote:
bill.sloman@ieee.org wrote:
As for rattling Phil Allison's cage - the longer we keep him mad, the
better the chance that he will blow a blood vessel and lose his
capacity to manipulate a keyboard. This would be a rather pyschopathic
motivation if one considered Phil to be fully human.
The same could be said for you, Bill.
But I said it first. You have to invent your own abuse if you want to
get any brownie points.
And I don't show much sign of blowing a blood vessel.
I don't want brownie points, Bill. Brownies are young girls on their
way to being Girls Scouts.
|
The Australian scouting movement uses the same name for that particular
age-group.
The concept has generalised over the years.
| Quote: | The first sign of blowing a blood vessel is
when it explodes.
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True, but the chances of it blowing depend pretty heavily on your blood
pressure. Mine is about 130/65.
--
Bill Sloman, Nijmegen |
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Bill Sloman
electronics forum Guru
Joined: 12 May 2005
Posts: 1080
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| Posted: Fri Jul 21, 2006 3:11 am Post subject:
Re: FREQ COUNTER help
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Michael A. Terrell wrote:
| Quote: | bill.sloman@ieee.org wrote:
John Fields wrote:
On 19 Jul 2006 02:46:44 -0700, bill.sloman@ieee.org wrote:
As for rattling Phil Allison's cage - the longer we keep him mad, the
better the chance that he will blow a blood vessel and lose his
capacity to manipulate a keyboard. This would be a rather pyschopathic
motivation if one considered Phil to be fully human.
---
When not having to deal with some of the less-than-human lifeforms
infecting this forum, Phil often comes into his own and offers
outstanding advice, I've found. YMMV.
On his chosen subjects he is pretty good, but he does degenerate into
snarling rage remarkably quickly, and he remains incensed for
remarkably long periods.
--
Bill Sloman, Nijmegen
Kind of like your insane anti America rants, old boy?
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This is "insane" in the Communist Russian sense - if you disagree with
my ideology you must be crazy and I have to lock you up in an insane
asylum until you see the logic of my position.
Try a little reasoned argument the next time you come across a poltical
opinion you don't like. Your education system doesn't exactly prepare
you for this sort of discussion, but it is a skill you ought to learn.
--
Bill Sloman, Nijmegen |
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Michael A. Terrell
electronics forum Guru
Joined: 24 Mar 2005
Posts: 2291
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| Posted: Fri Jul 21, 2006 5:33 am Post subject:
Re: FREQ COUNTER help
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bill.sloman@ieee.org wrote:
| Quote: |
This is "insane" in the Communist Russian sense - if you disagree with
my ideology you must be crazy and I have to lock you up in an insane
asylum until you see the logic of my position.
Try a little reasoned argument the next time you come across a poltical
opinion you don't like. Your education system doesn't exactly prepare
you for this sort of discussion, but it is a skill you ought to learn.
--
Bill Sloman, Nijmegen
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It is insane for you to sit on the other side of the world and try to
influence how I think. Maybe you could learn that, if you tried?
--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.
Michael A. Terrell
Central Florida |
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Paul Taylor
electronics forum beginner
Joined: 10 Feb 2005
Posts: 45
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| Posted: Fri Jul 21, 2006 8:20 am Post subject:
Re: FREQ COUNTER help
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<bill.sloman@ieee.org> wrote in message
| Quote: | It doesn't need to be synchronous. Only the first stage needs to be able
to start and stop in one cycle. The rest of it can be a ripple counter.
If you wait for things to calm down after the first stage is stopped, the
rippling will finish before you read the counter.
First counter I ever put on a printed circuit board worked that way - a
monstable stopped you reading the counter until the last count had
rippled all the way through. That was back in 1972.
Nowadays that sort of trickery is rarely necessary - though I did
extend an MC100E016 based counter with an 74HCT40103 a few years back
for a particularly cheap-skate customer. It cost more in design time
than it could ever save in parts costs, but it was quite fun to do.
--
Bill Sloman, Nijmegen
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That sounded like fun, we have plenty of the cheap skate customer coming
through, wanting something for nothing? |
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Paul Taylor
electronics forum beginner
Joined: 10 Feb 2005
Posts: 45
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| Posted: Fri Jul 21, 2006 8:25 am Post subject:
Re: FREQ COUNTER help
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"Rick" <rik_nntp@dsl.pipex.com> wrote in message
news:iqGdnQDDtYFxciLZnZ2dnUVZ8qWdnZ2d@pipex.net...
| Quote: | In the case that of a discriminator with
memory and a dead-time, that simplifies to "what's the length of that
memory of an event plus the deadtime", which is what you're now saying.
---
No, it's what _you're_ now saying. I always postulated a train of
maximum-density detectable pulses and you're only now coming around
to it while trying to make it seem like it's been your position all
along.
Trouble is, you define maximum density (see 2 or 3 of your posts ago) in
terms of the 1ms reporting period and in terms of the bit-width of the
counter. Better tell the PAD your assumptions.
--
Rick
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Rick 2 to the power of 16 is the maximum counter rate required! |
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Rick H
electronics forum beginner
Joined: 19 Jul 2005
Posts: 18
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| Posted: Fri Jul 21, 2006 12:26 pm Post subject:
Re: FREQ COUNTER help
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Paul Taylor <paul.taylor@uea.ac.uk> wrote:
| Quote: | "Rick" <rik_nntp@dsl.pipex.com> wrote in message
news:iqGdnQDDtYFxciLZnZ2dnUVZ8qWdnZ2d@pipex.net...
In the case that of a discriminator with
memory and a dead-time, that simplifies to "what's the length of that
memory of an event plus the deadtime", which is what you're now saying.
---
No, it's what _you're_ now saying. I always postulated a train of
maximum-density detectable pulses and you're only now coming around
to it while trying to make it seem like it's been your position all
along.
Trouble is, you define maximum density (see 2 or 3 of your posts ago) in
terms of the 1ms reporting period and in terms of the bit-width of the
counter. Better tell the PAD your assumptions.
--
Rick
Rick 2 to the power of 16 is the maximum counter rate required!
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Hi Paul,
Yes, we understand that you're designing the system to detect a maximum
of 65536 events per millisecond (Although I'm going to guess that
actually your maximum count is 65535, because that's the most a 16-bit
counter will give you).
This sub-thread started because John was estimating the accuracy
required of the ms timer - the one that says "stop counting and tell me
what you've got" - to be sure that the count is accurate to one event.
Well, you may not even be interested in 1-event accuracy, but that's the
way the conversation turned!
Clearly, the most error you can tolerate on a timer in order to make
sure the count is accurate to 1 event is related to the *minimum* time
between events. As an example (with made-up numbers, John), if your
clock toggles early by 10us and if the PAD happened to detect an extra
2 events in that extra 10us before the clock *should* have toggled, then
your count is out by two. The only way to ensure the count is accurate
to one event is to make sure that the ms clock transitions at 1ms +/-
the smallest possible time-gap between events.
John went about it in a different way - , he assumed that the PAD
would change its output (at its fastest, when lots of photons are being
detected) exactly 65536 times per ms. Obviously if that actually _was_
the case, then the minumum time between events becomes 1ms/65536 and that
therefore defines the accuracy of the ms clock neatly in terms of the
1ms period and the 16 bit width of the counter. But unless you can alter
the PAD's pulse time plus dead-time so that it's accurately 1/65536 ms,
that's not going to happen.
The difference between us is that I say "measure or look up the minimum
possible time between events and use that number to determine timer
accuracy", whereas John says "Assume that the minimum time between
events is (conveniently) 1/65536ms and take it from there".
As an aside, somewhere else in the thread, John suggested using the
PAD's output to gate a fast clock into the counter. If you do that, you
need to make sure that the fast clock is guaranteed to have exactly one
edge per event. Failure to do so will result in the PAD gating a clock
that's not currently doing anything (missed count) or gating a clock that
may transition more than once during the PAD's output pulse (multiple
counts per event). However, upon re-reading some of the thread, I
realise that John abandoned that idea, so my spiel in my last post about
lost/extra counts is redundant.
Anyway, good luck in building your project, Paul - I hope it's a success.
--
Rick |
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