pulse counter
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From: George Herold on 23 Mar 2010 14:55 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.
From: John Larkin on 23 Mar 2010 16:05 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.) > >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. It's probably a trigger level problem. I don't think B&K actually makes anything any more... they jsut rebrand it. John
From: George Herold on 23 Mar 2010 22:11 On Mar 23, 4:05 pm, John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> 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.) > > >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 wed 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.
From: John Fields on 24 Mar 2010 09:18 On Tue, 23 Mar 2010 19:11:41 -0700 (PDT), George Herold <ggherold(a)gmail.com> wrote: >On Mar 23, 4:05�pm, John Larkin ><jjlar...(a)highNOTlandTHIStechnologyPART.com> 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.) >> >> >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
From: George Herold on 24 Mar 2010 09:52
On Mar 24, 9:18 am, John Fields <jfie...(a)austininstruments.com> wrote: > On Tue, 23 Mar 2010 19:11:41 -0700 (PDT), George Herold > > > > > > <ggher...(a)gmail.com> wrote: > >On Mar 23, 4:05 pm, John Larkin > ><jjlar...(a)highNOTlandTHIStechnologyPART.com> 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.) > > >> >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 wed 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 - 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(a)teachspin.com I could give you some simple specs and maybe you have some idea of a 'ball park' price. George H. |