Magnus,
Thanks for the detailed reply and history.
The counter (just got it recently) came with the Fluke CD which had an
op manual on it. I also found the CNT-81 manual on a Pendulum site. They
seem to have identical content except for name changes. One note, if
anyone else has one of these
On 06/09/2011 07:30 PM, Peter Vince wrote:
Hi Rex,
You could try asking the guys at Pendulum. A couple of them came
down a gave a talk at the UK's National Physical Laboratory "Time&
Frequency Club" meeting a few years ago and were very interesting and
approachable. It looks like they mi
Hi Rex,
You could try asking the guys at Pendulum. A couple of them came
down a gave a talk at the UK's National Physical Laboratory "Time &
Frequency Club" meeting a few years ago and were very interesting and
approachable. It looks like they might have been swallowed by
Spectracom now - s
richt-
Von: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] Im Auftrag
von Rex
Gesendet: Montag, 6. Juni 2011 00:42
An: Discussion of precise time and frequency measurement
Betreff: Re: [time-nuts] Fluke PM6681 triggering
I forgot that I had a 50 ohm load on the scope end of my cabl
of precise time and frequency measurement
Betreff: Re: [time-nuts] Fluke PM6681 triggering
I forgot that I had a 50 ohm load on the scope end of my cable for that
picture. The audio output is cap coupled. That's why the short pulse
with long exponential tail. If I use 1M input at the scope it
I forgot that I had a 50 ohm load on the scope end of my cable for that
picture. The audio output is cap coupled. That's why the short pulse
with long exponential tail. If I use 1M input at the scope it is a
square pulse >200 uS but still has that glitch on the leading edge.
I put a simple RC
Hi Rex,
I think Bruce has hit it on the old nail head. Especially now that I have a
schematic to look at.
You indicated you changed the tube to a different one, is that right ? I wonder
if it may be a characteristic of the new tube you are using ? Maybe it needs a
higher voltage to cause a sta
Crap. Maybe you are right. I didn't need another project. Trying to
decide if I should investigate, ignore it, or just move on to a better
interface.
On 6/5/2011 3:53 AM, Bruce Griffiths wrote:
Maybe, but the circuit diagram indicates that the pulse that you see
is nothing like what it should
Maybe, but the circuit diagram indicates that the pulse that you see is
nothing like what it should be.
There may well be a circuit fault.
The circuit already includes a monostable.
Bruce
Rex wrote:
We are getting pretty far afield of my original counter triggering
question.
As far as I know
We are getting pretty far afield of my original counter triggering question.
As far as I know, any specific quenching is only necessary for achieving
the highest counting rates which isn't involved in my measurements, so
far as I know.
Like I said, this is a 1960's CD counter. Pretty impressi
Is the GM tube internally or externally quenched?
Its necessary to quench each avalanche discharge either by using an
internal quenching gas (eg a halogen) or to use suitable circuitry to
ensure the discharge terminates.
Bruce
Rex wrote:
Bill and Bruce,
Clearly, fixing the messed up signal
Bill and Bruce,
Clearly, fixing the messed up signal is the proper approach. What you
are missing is that I got a shiney new (for me) expensive hammer and I
thought that it should be able to drive defective nails. :)
I got an off-list reply that suggested that hold-off affects the counter
ga
A Geiger Muller (GM) tube produces an output pulse as a result of an
avalanche discharge in the gas filled tube initiated by the passage of
ionising radiation through the tube.
A high voltage is initially maintained between an outer usually
cylindrical electrode and an inner small diameter wire
Hi again Rex,
I should have asked these questions in the first place.
How are you connecting the Fluke to the geiger counter ?
Is this a signal that drives a speaker or some other kind of noise maker ?
What happens if you load that line with some capacitance like 1 uf or more ?
If the capacita
Hi Rex,
I am not familiar with that counter, but I am wondering if you could use a
"one-shot" to clean up that problem ? Something similar to the 74121 or 74122.
Make sure you do not select a "re-triggerable" type (74123) as that will follow
the apparent double pulse. You might see if there is a
I recently picked up a Fluke PM6681 counter (same as a Pendulum CNT-81).
Looks like a sweet device.
I was just trying to use it for a not-so-much-timing purpose and was
hoping to find an expert here who might help me with a triggering question.
I just set it up to count total pulses, over a 5
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