pulse counter

G

George Herold

Guest
I want to count TTL pulses from a PMT. (There is already some pulse
shaping and discriminator electronics between the PMT and output.)
The TTL pulses have a fixed width of 300ns and a rate from 10 Hz to
several hundred kHz (coming at random times). In the good-old-days
all the frequency counters did this just fine. You selected a gate
time and the thing just counted the number of transitions in that time
window. Exactly what I want. The counters they are selling today
seem to measure the period and then invert it to tell me the
frequency. Not at all what I want. Anyone know of old style counters
still for sale. (Not ebay or used stuff please these are to send to
our customers.)

We are using these,
http://www.bkprecision.com/products/model/1803D/200-mhz-frequency-counter.html

Which 'almost' work. The count rate from the random photons should
have a Poisson distribution. When I make a histogram of the counts
from the above meter there is not enough variation in the output. On
the front panel it says it's counting for one second, but it's doing
something else... either counting for two seconds and dividing by two
or it's averaging over a few seconds. I wouldn't mind either if they
would just tell me what it's doing.... Yes I've emailed and called
tech support at B&K... still waiting.

Thanks,

George H.
 
On Tue, 23 Mar 2010 11:55:15 -0700 (PDT), George Herold
<ggherold@gmail.com> wrote:

I want to count TTL pulses from a PMT. (There is already some pulse
shaping and discriminator electronics between the PMT and output.)
The TTL pulses have a fixed width of 300ns and a rate from 10 Hz to
several hundred kHz (coming at random times). In the good-old-days
all the frequency counters did this just fine. You selected a gate
time and the thing just counted the number of transitions in that time
window. Exactly what I want. The counters they are selling today
seem to measure the period and then invert it to tell me the
frequency. Not at all what I want. Anyone know of old style counters
still for sale. (Not ebay or used stuff please these are to send to
our customers.)

We are using these,
http://www.bkprecision.com/products/model/1803D/200-mhz-frequency-counter.html

Which 'almost' work. The count rate from the random photons should
have a Poisson distribution. When I make a histogram of the counts
from the above meter there is not enough variation in the output. On
the front panel it says it's counting for one second, but it's doing
something else... either counting for two seconds and dividing by two
or it's averaging over a few seconds. I wouldn't mind either if they
would just tell me what it's doing.... Yes I've emailed and called
tech support at B&K... still waiting.

Thanks,

George H.
Click to expand...
It's probably a trigger level problem.

I don't think B&K actually makes anything any more... they jsut
rebrand it.

John
 
On Mar 23, 4:05 pm, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Tue, 23 Mar 2010 11:55:15 -0700 (PDT), George Herold





ggher...@gmail.com> wrote:
I want to count TTL pulses from a PMT.  (There is already some pulse
shaping and discriminator electronics between the PMT and output.)
The TTL pulses have a fixed width of 300ns and a rate from 10 Hz to
several hundred kHz (coming at random times).  In the good-old-days
all the frequency counters did this just fine.  You selected a gate
time and the thing just counted the number of transitions in that time
window.  Exactly what I want.  The counters they are selling today
seem to measure the period and then invert it to tell me the
frequency.  Not at all what I want.  Anyone know of old style counters
still for sale.  (Not ebay or used stuff please these are to send to
our customers.)

We are using these,
http://www.bkprecision.com/products/model/1803D/200-mhz-frequency-cou...

Which 'almost' work.  The count rate from the random photons should
have a Poisson distribution.  When I make a histogram of the counts
from the above meter there is not enough variation in the output.  On
the front panel it says it's counting for one second, but it's doing
something else... either counting for two seconds and dividing by two
or it's averaging over a few seconds.  I wouldn't mind either if they
would just tell me what it's doing.... Yes I've emailed and called
tech support at B&K... still waiting.

Thanks,

George H.

It's probably a trigger level problem.

I don't think B&K actually makes anything any more... they jsut
rebrand it.

John- Hide quoted text -

- Show quoted text -
Click to expand...

Oh it doesn't seem to be a trigger level problem. All the pulses are
the same height and width.... how can you screw that up? The average
value of the count rate is fine. There are just not enough counts out
on the wings. You've got to record a bunch of numbers, plot them up
and look at the statistics.

I figure who ever designed the thing no longer works there and no-one
can answer my question. (They have no idea how it works.) We can
build our own pulse counter, but that just costs a fortune when we're
only going to sell ten or so a year.... I'd really like someone else
to do it. Still at least then we’d know how it works.

There are Nim bin and Camac things that can count pulses but those
prices seem over the top too. (You've gotta buy the bin after all.)

Sigh,
George H.
 
On Tue, 23 Mar 2010 19:11:41 -0700 (PDT), George Herold
<ggherold@gmail.com> wrote:

On Mar 23, 4:05 pm, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Tue, 23 Mar 2010 11:55:15 -0700 (PDT), George Herold





ggher...@gmail.com> wrote:
I want to count TTL pulses from a PMT.  (There is already some pulse
shaping and discriminator electronics between the PMT and output.)
The TTL pulses have a fixed width of 300ns and a rate from 10 Hz to
several hundred kHz (coming at random times).  In the good-old-days
all the frequency counters did this just fine.  You selected a gate
time and the thing just counted the number of transitions in that time
window.  Exactly what I want.  The counters they are selling today
seem to measure the period and then invert it to tell me the
frequency.  Not at all what I want.  Anyone know of old style counters
still for sale.  (Not ebay or used stuff please these are to send to
our customers.)

We are using these,
http://www.bkprecision.com/products/model/1803D/200-mhz-frequency-cou...

Which 'almost' work.  The count rate from the random photons should
have a Poisson distribution.  When I make a histogram of the counts
from the above meter there is not enough variation in the output.  On
the front panel it says it's counting for one second, but it's doing
something else... either counting for two seconds and dividing by two
or it's averaging over a few seconds.  I wouldn't mind either if they
would just tell me what it's doing.... Yes I've emailed and called
tech support at B&K... still waiting.

Thanks,

George H.

It's probably a trigger level problem.

I don't think B&K actually makes anything any more... they jsut
rebrand it.

John- Hide quoted text -

- Show quoted text -


Oh it doesn't seem to be a trigger level problem. All the pulses are
the same height and width.... how can you screw that up? The average
value of the count rate is fine. There are just not enough counts out
on the wings. You've got to record a bunch of numbers, plot them up
and look at the statistics.

I figure who ever designed the thing no longer works there and no-one
can answer my question. (They have no idea how it works.) We can
build our own pulse counter, but that just costs a fortune when we're
only going to sell ten or so a year.... I'd really like someone else
to do it. Still at least then we’d know how it works.
Click to expand...
---
We can build you something which will do exactly what you want
without the expense of all the added frills.

Email me or call me at 512 339 9020 if you're interested.

JF
 
On Mar 24, 9:18 am, John Fields <jfie...@austininstruments.com> wrote:
On Tue, 23 Mar 2010 19:11:41 -0700 (PDT), George Herold





ggher...@gmail.com> wrote:
On Mar 23, 4:05 pm, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Tue, 23 Mar 2010 11:55:15 -0700 (PDT), George Herold

ggher...@gmail.com> wrote:
I want to count TTL pulses from a PMT.  (There is already some pulse
shaping and discriminator electronics between the PMT and output.)
The TTL pulses have a fixed width of 300ns and a rate from 10 Hz to
several hundred kHz (coming at random times).  In the good-old-days
all the frequency counters did this just fine.  You selected a gate
time and the thing just counted the number of transitions in that time
window.  Exactly what I want.  The counters they are selling today
seem to measure the period and then invert it to tell me the
frequency.  Not at all what I want.  Anyone know of old style counters
still for sale.  (Not ebay or used stuff please these are to send to
our customers.)

We are using these,
http://www.bkprecision.com/products/model/1803D/200-mhz-frequency-cou....

Which 'almost' work.  The count rate from the random photons should
have a Poisson distribution.  When I make a histogram of the counts
from the above meter there is not enough variation in the output.  On
the front panel it says it's counting for one second, but it's doing
something else... either counting for two seconds and dividing by two
or it's averaging over a few seconds.  I wouldn't mind either if they
would just tell me what it's doing.... Yes I've emailed and called
tech support at B&K... still waiting.

Thanks,

George H.

It's probably a trigger level problem.

I don't think B&K actually makes anything any more... they jsut
rebrand it.

John- Hide quoted text -

- Show quoted text -

Oh it doesn't seem to be a trigger level problem.  All the pulses are
the same height and width.... how can you screw that up?  The average
value of the count rate is fine.  There are just not enough counts out
on the wings.  You've got to record a bunch of numbers, plot them up
and look at the statistics.

I figure who ever designed the thing no longer works there and no-one
can answer my question.  (They have no idea how it works.) We can
build our own pulse counter, but that just costs a fortune when we're
only going to sell ten or so a year.... I'd really like someone else
to do it.   Still at least then we’d know how it works.

---
We can build you something which will do exactly what you want
without the expense of all the added frills.

Email me or call me at 512 339 9020 if you're interested.

JF- Hide quoted text -

- Show quoted text -
Click to expand...
Hi John, Well that may be one solution. Problem is we really don't
sell many units.
So price is a bit sticky... I have no idea how much you charge for
such a relatively simple design. The counter hangs on the end of ths
piece of apparatus.

http://www.teachspin.com/instruments/two_slit/index.shtml

We sell maybe 20-30 a year, and hope to go on selling it for many
more. Many schools already have counters and so perhaps only 1/2 of
the users need to buy a counter.

The two slit is not my baby and my boss is responsible for most of the
'upkeep' of the instrument. He's still sort of flaiing around, trying
to decide what to do.

You can email me at,
gherold@teachspin.com

I could give you some simple specs and maybe you have some idea of a
'ball park' price.

George H.
 
On Mar 23, 11:55 am, George Herold <ggher...@gmail.com> wrote:
I want to count TTL pulses from a PMT.  (There is already some pulse
shaping and discriminator electronics between the PMT and output.)
The TTL pulses have a fixed width of 300ns and a rate from 10 Hz to
several hundred kHz (coming at random times).  In the good-old-days
all the frequency counters did this just fine.  You selected a gate
time and the thing just counted the number of transitions in that time
Click to expand...
Red Lion Controls 'sub-cub' counter is a kind of panel-meter module
that does simple counting. It might simplify the build-your-own
option.

<http://www.redlion.net/Products/Groups/DigitalInputs/SCUB1/2/Docs/
09008.pdf>

Are you accounting for pile-up effects at high count rates?
 
On Mar 24, 5:34 pm, whit3rd <whit...@gmail.com> wrote:
On Mar 23, 11:55 am, George Herold <ggher...@gmail.com> wrote:

I want to count TTL pulses from a PMT.  (There is already some pulse
shaping and discriminator electronics between the PMT and output.)
The TTL pulses have a fixed width of 300ns and a rate from 10 Hz to
several hundred kHz (coming at random times).  In the good-old-days
all the frequency counters did this just fine.  You selected a gate
time and the thing just counted the number of transitions in that time

Red Lion Controls 'sub-cub' counter is a kind of panel-meter module
that does simple counting.  It might simplify the build-your-own
option.

http://www.redlion.net/Products/Groups/DigitalInputs/SCUB1/2/Docs/
09008.pdf

Are you accounting for pile-up effects at high count rates?
Click to expand...
Thanks Whit3rd, the 10kHz count rate won't cut it.

It looks like we're just going to build our own. Turns out the boss
was never happy with the discriminator on the current module. So
we'll put our own threshold level into the front end and detect ~100mV
pulses and not the TTL's. I was going to use a LM393 comparator,
which I've used before. So at least we'll be adding a bit of value.
A co-worker wants to squirt the count number out a usb port, which
sounds like a good idea. (Hmm, I'm going to have to understand how
that works.)


George H.
 
On Tue, 23 Mar 2010 11:55:15 -0700 (PDT), George
Herold <ggherold@gmail.com> wrote:

I want to count TTL pulses from a PMT. (There is already some pulse
shaping and discriminator electronics between the PMT and output.)
The TTL pulses have a fixed width of 300ns and a rate from 10 Hz to
several hundred kHz (coming at random times). In the good-old-days
all the frequency counters did this just fine. You selected a gate
time and the thing just counted the number of transitions in that time
window. Exactly what I want. The counters they are selling today
seem to measure the period and then invert it to tell me the
frequency. Not at all what I want. Anyone know of old style counters
still for sale. (Not ebay or used stuff please these are to send to
our customers.)
Click to expand...
I think the "new" type you are trying to avoid is
typically called "intelligent counter" or words to
that effect. So you might want to look at
manufacturers that offer both "intelligent"
models, and other models that don't claim to be
intelligent.

A quick Web search for "cheap frequency counter"
turned up the Instek GFC-8010H at $175.50 from
<www.tequipment.net> (in the adevertising sidebar
on the right panel of the Google page). The same
company offers 2 other Instek models that claim to
be "intelligent", so I assume that this one is
not. (But I don't know for sure.)

Best regards,


Bob Masta

DAQARTA v5.10
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, FREE Signal Generator
Pitch Track, Pitch-to-MIDI
DaqMusic - FREE MUSIC, Forever!
(Some assembly required)
Science (and fun!) with your sound card!
 
On Mar 25, 9:52 am, N0S...@daqarta.com (Bob Masta) wrote:
On Tue, 23 Mar 2010 11:55:15 -0700 (PDT), George

Herold <ggher...@gmail.com> wrote:
I want to count TTL pulses from a PMT.  (There is already some pulse
shaping and discriminator electronics between the PMT and output.)
The TTL pulses have a fixed width of 300ns and a rate from 10 Hz to
several hundred kHz (coming at random times).  In the good-old-days
all the frequency counters did this just fine.  You selected a gate
time and the thing just counted the number of transitions in that time
window.  Exactly what I want.  The counters they are selling today
seem to measure the period and then invert it to tell me the
frequency.  Not at all what I want.  Anyone know of old style counters
still for sale.  (Not ebay or used stuff please these are to send to
our customers.)

I think the "new" type you are trying to avoid is
typically called "intelligent counter" or words to
that effect.  So you might want to look at
manufacturers that offer both "intelligent"
models, and other models that don't claim to be
intelligent.  

A quick Web search for "cheap frequency counter"
turned up the Instek GFC-8010H at $175.50 from
www.tequipment.net> (in the adevertising sidebar
on the right panel of the Google page).  The same
company offers 2 other Instek models that claim to
be "intelligent", so I assume that this one is
not.  (But I don't know for sure.)

Best regards,

Bob Masta

              DAQARTA  v5.10
   Data AcQuisition And Real-Time Analysis
             www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
    Frequency Counter, FREE Signal Generator
           Pitch Track, Pitch-to-MIDI
         DaqMusic - FREE MUSIC, Forever!
             (Some assembly required)
     Science (and fun!) with your sound card!
Click to expand...
Thank Bob, my Boss has looked at a whole bunch of different
commercial units from Protek, B&K, I'm not sure if we looked at any
from Instek. It looks like we are going to build our own. At least
then we know what is going on inside.

I was playing with a LM393 (dual of the LM339) today. These are a bit
slower than I'd like. Any favorite compartors with perhaps a 50
-100nS response time? LM311?

George H.
 
On 2010-03-25, George Herold <ggherold@gmail.com> wrote:
On Mar 25, 9:52 am, N0S...@daqarta.com (Bob Masta) wrote:


Thank Bob, my Boss has looked at a whole bunch of different
commercial units from Protek, B&K, I'm not sure if we looked at any
from Instek. It looks like we are going to build our own. At least
then we know what is going on inside.
Click to expand...
it seems to me that frequency counters are for measuring singals that
have a frequency that can be measured un Hz. the randomly distributed
pulses from a photomultiplier or a geiger tube can't.

I was playing with a LM393 (dual of the LM339) today. These are a bit
slower than I'd like.
Click to expand...
what do you expect for less than 25c :)

Any favorite compartors with perhaps a 50
-100nS response time? LM311?
Click to expand...
LM319 is at slow end of that range.

hit an online electronic supplier site like digikey, newark, or mouser
type "comparitor" into the search box and pick your desired parameters








--- news://freenews.netfront.net/ - complaints: news@netfront.net ---
 
On 26 Mar 2010 08:17:53 GMT, Jasen Betts <jasen@xnet.co.nz> wrote:

On 2010-03-25, George Herold <ggherold@gmail.com> wrote:
On Mar 25, 9:52 am, N0S...@daqarta.com (Bob Masta) wrote:


Thank Bob, my Boss has looked at a whole bunch of different
commercial units from Protek, B&K, I'm not sure if we looked at any
from Instek. It looks like we are going to build our own. At least
then we know what is going on inside.

it seems to me that frequency counters are for measuring singals that
have a frequency that can be measured un Hz. the randomly distributed
pulses from a photomultiplier or a geiger tube can't.

I was playing with a LM393 (dual of the LM339) today. These are a bit
slower than I'd like.

what do you expect for less than 25c :)

Any favorite compartors with perhaps a 50
-100nS response time? LM311?

LM319 is at slow end of that range.

hit an online electronic supplier site like digikey, newark, or mouser
type "comparitor" into the search box and pick your desired parameters
Click to expand...
---
I tried it on DigiKey and got back "No records match your search
criteria."

How can that be???

JF
 
On Fri, 26 Mar 2010 08:43:29 -0500, John Fields
<jfields@austininstruments.com> wrote:


hit an online electronic supplier site like digikey, newark, or mouser
type "comparitor" into the search box and pick your desired parameters

---
I tried it on DigiKey and got back "No records match your search
criteria."

How can that be???

JF
Try "comparator". ;-)
Click to expand...
 
On Thu, 25 Mar 2010 13:15:08 -0700 (PDT), George Herold
<ggherold@gmail.com> wrote:


Thank Bob, my Boss has looked at a whole bunch of different
commercial units from Protek, B&K, I'm not sure if we looked at any
from Instek. It looks like we are going to build our own. At least
then we know what is going on inside.

I was playing with a LM393 (dual of the LM339) today. These are a bit
slower than I'd like. Any favorite compartors with perhaps a 50
-100nS response time? LM311?

George H.
Click to expand...
Have a look at Analog Devices - they have a couple with TTL or CMOS
outputs with 7 - 8 ns propagation delay.



--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca
 
On Mar 24, 6:31 pm, George Herold <ggher...@gmail.com> wrote:

Red Lion Controls 'sub-cub' counter...
Are you accounting for pile-up effects at high count rates?

Thanks Whit3rd, the 10kHz count rate won't cut it.
Click to expand...
It's about 500 kHz (that 10 kHz number was 3V worst case value).

Yeah, the counter is a tad underpowered. Most micros (the PICs
in particular) are weak on counter functions. Best bet is something
with a true counter/timer module, and some preprocessing to
take out pile-up like an up/down pre-counter. Clock UP on input
signal, DOWN iff nonzero, in synchrony with a local clock,
incrementing
the slow counter at a steady rate... a couple of stages of
74F193 can gobble lots of pulses fast, and disgorge at
a compliant rate to the main counter. Your CPU count
is only correct after the pre-counter finishes unloading, of course.
 
On Mar 26, 11:58 am, Peter Bennett <pete...@somewhere.invalid> wrote:
On Thu, 25 Mar 2010 13:15:08 -0700 (PDT), George Herold

ggher...@gmail.com> wrote:
Thank Bob,  my Boss has looked at a whole bunch of different
commercial units from Protek, B&K, I'm not sure if we looked at any
from Instek.  It looks like we are going to build our own.  At least
then we know what is going on inside.

I was playing with a LM393 (dual of the LM339) today.  These are a bit
slower than I'd like.  Any favorite compartors with perhaps a 50
-100nS response time?  LM311?

George H.

Have a look at Analog Devices - they have a couple with TTL or CMOS
outputs with 7 - 8 ns propagation delay.

--
Peter Bennett, VE7CEI  
peterbb4 (at) interchange.ubc.ca  
GPS and NMEA info:http://vancouver-webpages.com/peter
Vancouver Power Squadron:http://vancouver.powersquadron.ca
Click to expand...
Thanks Peter, I was thinking today that maybe the spec I care about
is the slew rate. I'd like it to get to 5V in about 100nS.. 50V/us.
I don't think I care too much about the propigation delay. (But I
could be wrong... I've only used the slow lm393 for switching low
frequency stuff <1MHz.) I just don't want to miss two close together
pulses.
 
On Mar 26, 3:57 pm, whit3rd <whit...@gmail.com> wrote:
On Mar 24, 6:31 pm, George Herold <ggher...@gmail.com> wrote:

Red Lion Controls 'sub-cub' counter...
Are you accounting for pile-up effects at high count rates?

Thanks Whit3rd, the 10kHz count rate won't cut it.

It's about 500 kHz (that 10 kHz number was 3V worst case value).

Yeah, the counter is a tad underpowered.  Most micros (the PICs
in particular) are weak on counter functions.   Best bet is something
with a true counter/timer module, and some preprocessing to
take out pile-up like an up/down pre-counter.  Clock UP on input
signal, DOWN iff nonzero, in synchrony with a local clock,
incrementing
the slow counter at a steady rate... a couple of stages of
74F193 can gobble lots of pulses fast, and disgorge at
a compliant rate to the main counter.    Your CPU count
is only correct after the pre-counter finishes unloading, of course.
Click to expand...
Ahh 500kHz on the red lion... that could almost do it. I should have
looked at the specs more carefully. 1 MHz is the maximum needed count
rate and most of the time it's counting 100's of pulses a second.

You mentioned 'pulse pile-up' before, But I don't know exactly what
you are talking about. At high count rates I'll sometimes have two
pulses arriving at time's that are below the resolution of front end.
I'll just count these as one event. But you seem to be impling some
pile up at the counter. Will this be a problem at a mximum 1MHz
count rate?

Thanks,

George H.
 
In article <f1426257-ef50-4545-ae17-790024fdbb6d@j21g2000yqh.googlegroups.com>,
George Herold <ggherold@gmail.com> wrote:
I was playing with a LM393 (dual of the LM339) today. These are a bit
slower than I'd like. Any favorite compartors with perhaps a 50
-100nS response time? LM311?
Click to expand...
Back about 25 years ago, I tried the LM311 as video amplifer to
feed a TTL input CRT monitor. More like 200 nS, as I remember.
(Replaced it with a NE592 video amp).

One of the oufits in Florida (Optoelectronics or one of their
competitors) used the LT1016(?) comparator as the input for one of
their frequency counter kit projects in Radio-Electronics magazine
back in the '80s. I think it's good for 20 nS.

Mark Zenier mzenier@eskimo.com
Googleproofaddress(account:mzenier provider:eskimo domain:com)
 
On Fri, 26 Mar 2010 14:15:54 -0700 (PDT), George Herold
<ggherold@gmail.com> wrote:

On Mar 26, 11:58 am, Peter Bennett <pete...@somewhere.invalid> wrote:
On Thu, 25 Mar 2010 13:15:08 -0700 (PDT), George Herold

ggher...@gmail.com> wrote:
Thank Bob,  my Boss has looked at a whole bunch of different
commercial units from Protek, B&K, I'm not sure if we looked at any
from Instek.  It looks like we are going to build our own.  At least
then we know what is going on inside.

I was playing with a LM393 (dual of the LM339) today.  These are a bit
slower than I'd like.  Any favorite compartors with perhaps a 50
-100nS response time?  LM311?

George H.

Have a look at Analog Devices - they have a couple with TTL or CMOS
outputs with 7 - 8 ns propagation delay.

--
Peter Bennett, VE7CEI  
peterbb4 (at) interchange.ubc.ca  
GPS and NMEA info:http://vancouver-webpages.com/peter
Vancouver Power Squadron:http://vancouver.powersquadron.ca

Thanks Peter, I was thinking today that maybe the spec I care about
is the slew rate. I'd like it to get to 5V in about 100nS.. 50V/us.
I don't think I care too much about the propigation delay. (But I
could be wrong... I've only used the slow lm393 for switching low
frequency stuff <1MHz.) I just don't want to miss two close together
pulses.
Click to expand...
---
Then what you have to decide on is the criterion which determines what's
one pulse and what's more than one, and then devise a strategy to
determine how many pulses have gone by.

JF
 
On Mar 26, 2:35 pm, George Herold <ggher...@gmail.com> wrote:

You mentioned 'pulse pile-up' before, But I don't know exactly what
you are talking about. At high count rates I'll sometimes have two
pulses arriving at time's that are below the resolution of front end.
Click to expand...
Yes, basically that's it. The pulses (300 ns) can be too close
together
for the counter to resolve, and a (say 100 kHz) counter might
need a wider pulse or spacing. 100 kHz applies to 50% duty cycle
clock, i.e. 5 us pulses, with 5 us spacing. Fast counters (74F193
does
over 100 MHz) can handle the 300 ns pulses, and down to 5 ns spaces
between pulses. The dead time of the system is then calculable,
instead of being unknown and unknowable.

The average frequency is misleading in terms of the individual random
times of pulses... and the market for 'frequency counters' doesn't
support
the timing requirements of pulse counting with appropriate
specifications.
 
On Mar 27, 1:46 pm, whit3rd <whit...@gmail.com> wrote:
On Mar 26, 2:35 pm, George Herold <ggher...@gmail.com> wrote:

You mentioned 'pulse pile-up' before, But I don't know exactly what
you are talking about.  At high count rates I'll sometimes have two
pulses arriving at time's that are below the resolution of front end.

Yes, basically that's it.  The pulses (300 ns) can be too close
together
for the counter to resolve, and a (say 100 kHz) counter might
need a wider pulse or spacing.  100 kHz applies to 50% duty cycle
clock, i.e. 5 us pulses, with 5 us spacing.   Fast counters (74F193
does
over 100 MHz) can handle the 300 ns pulses, and down to 5 ns spaces
between pulses.   The dead time of the system is then calculable,
instead of being unknown and unknowable.

The average frequency is misleading in terms of the individual random
times of pulses... and the market for 'frequency counters' doesn't
support
the timing requirements of pulse counting with appropriate
specifications.
Click to expand...
OK thanks, The existing front end elecronics gives a pulse with
~100ns rise time and >300ns fall time. (Kinda crappy for a PMT,) And
I'll live with that. Most of the time the counting rates are really
low... 10's to 1,000's per second. At high rates there is some error
due to pulse overlap... we'll just ignore it.

George H.
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top