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From: whit3rd on 24 Mar 2010 17:34
On Mar 23, 11:55 am, George Herold <ggher...(a)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?
From: George Herold on 24 Mar 2010 21:31
On Mar 24, 5:34 pm, whit3rd <whit...(a)gmail.com> wrote:
> On Mar 23, 11:55 am, George Herold <ggher...(a)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?

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.

From: Bob Masta on 25 Mar 2010 09:52
On Tue, 23 Mar 2010 11:55:15 -0700 (PDT), George
Herold <ggherold(a)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!
From: George Herold on 25 Mar 2010 16:15
On Mar 25, 9:52 am, N0S...(a)daqarta.com (Bob Masta) wrote:
> On Tue, 23 Mar 2010 11:55:15 -0700 (PDT), George
>
> Herold <ggher...(a)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!

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.
From: Jasen Betts on 26 Mar 2010 04:17
On 2010-03-25, George Herold <ggherold(a)gmail.com> wrote:
> On Mar 25, 9:52 am, N0S...(a)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








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