I need of a Geiger counter to do radiation measurements of x-ray
equipment, cabinets, etc. Since these are numbers going into FDA
reports the counter has to be calibrated and meet all requirements for
the US. Something like a Bicron Surveyor would work quite well. I
would like to get a digital unit that could be used for long term
measurement (downloadable to a computer), though. So the requirements
a

1) Constant real-time measurement, i.e. not just one measurement for
one button click plus quick response time.
2) Beeper that beeps quicker and/or louder depending on the mR/h
measured.
3) Digital read-out for long term measurement.

There are two units I have seen:

1) http://www.gammascout.com/
2) http://www.imagesco.com/geiger/digit...r-counter.html

Any input is highly appreciated.

wrote:
Since these are numbers going into FDA
reports the counter has to be calibrated


Might want to look at the calibration rules a little harder. The rules
could say that it has to be locally calibrated after shipment from the
factory. If so, you might want to call around to some local labs to see
what they say about this.

On Jul 24, 10:23 am, Vey wrote:

Since these are numbers going into FDA

reports the counter has to be calibrated

Might want to look at the calibration rules a little harder. The rules
could say that it has to be locally calibrated after shipment from the
factory. If so, you might want to call around to some local labs to see
what they say about this.

Thanks for the response. That's a good point. What confuses the heck
out of me is why the two units I listed are so cheap (like many
others, too). They cost like $400. An analog or digital unit from one
of the well known brands (Bicron/NDS/Ludlum) are huge and and cost
from $600 (analog)-$3000 (digital). Where does that price difference
come from and should I care about it (the functional difference, not
price difference)?

On Tue, 24 Jul 2007 09:37:25 -0700, "
wrote:

I need of a Geiger counter to do radiation measurements of x-ray
equipment, cabinets, etc. Since these are numbers going into FDA
reports the counter has to be calibrated and meet all requirements for
the US. Something like a Bicron Surveyor would work quite well. I
would like to get a digital unit that could be used for long term
measurement (downloadable to a computer), though. So the requirements
a

1) Constant real-time measurement, i.e. not just one measurement for
one button click plus quick response time.
2) Beeper that beeps quicker and/or louder depending on the mR/h
measured.
3) Digital read-out for long term measurement.

There are two units I have seen:

1) http://www.gammascout.com/
2) http://www.imagesco.com/geiger/digit...r-counter.html

Any input is highly appreciated.

Geigers are not used for medical X-rays.
The energy spectrum of geiger tubes forbids that.

You may use either a ionisation chamber, or even better
a modern cadmium-zink-telluride sensor.

There are very stringent rules how to monitor medical equipment
and you better contact the manufacturers of your machines.

w.

On Jul 24, 12:04 pm, H. Wabnig .... .-- .- -... -. .. --.
@ .- --- -. DOT .- - wrote:
On Tue, 24 Jul 2007 09:37:25 -0700, "




I need of a Geiger counter to do radiation measurements of x-ray
equipment, cabinets, etc. Since these are numbers going into FDA
reports the counter has to be calibrated and meet all requirements for
the US. Something like a Bicron Surveyor would work quite well. I
would like to get a digital unit that could be used for long term
measurement (downloadable to a computer), though. So the requirements
a

1) Constant real-time measurement, i.e. not just one measurement for
one button click plus quick response time.
2) Beeper that beeps quicker and/or louder depending on the mR/h
measured.
3) Digital read-out for long term measurement.

There are two units I have seen:

1)http://www.gammascout.com/
2)http://www.imagesco.com/geiger/digit...r-counter.html

Any input is highly appreciated.

Geigers are not used for medical X-rays.
The energy spectrum of geiger tubes forbids that.

You may use either a ionisation chamber, or even better
a modern cadmium-zink-telluride sensor.

There are very stringent rules how to monitor medical equipment
and you better contact the manufacturers of your machines.

w.- Hide quoted text -

- Show quoted text -


w.

Thanks for the input. This is actually not for a medical device. FDA
does not just regulate medical devices but also for instance x-ray
cabinet systems. They have certain requirements that need to be met
for these kind of devices. One stipulation is that you cannot exceed
0.5mR/h 5cm from the cabinet. So I need a device that can verify this
reliably. If any of the cheap ($500) digital devices I mentioned can
do this then that's fine. Do they?

I'm still puzzled why there are such huge differences between
different devices ($500 vs $3000).

Since we use tube voltages similar to medical I am intersted in your
statement that a GM tube can't be used. Why is that?

wrote:
On Jul 24, 12:04 pm, H. Wabnig .... .-- .- -... -. .. --.
@ .- --- -. DOT .- - wrote:
On Tue, 24 Jul 2007 09:37:25 -0700, "




I need of a Geiger counter to do radiation measurements of x-ray
equipment, cabinets, etc. Since these are numbers going into FDA
reports the counter has to be calibrated and meet all requirements for
the US. Something like a Bicron Surveyor would work quite well. I
would like to get a digital unit that could be used for long term
measurement (downloadable to a computer), though. So the requirements
a
1) Constant real-time measurement, i.e. not just one measurement for
one button click plus quick response time.
2) Beeper that beeps quicker and/or louder depending on the mR/h
measured.
3) Digital read-out for long term measurement.
There are two units I have seen:
1)http://www.gammascout.com/
2)http://www.imagesco.com/geiger/digit...r-counter.html
Any input is highly appreciated.
Geigers are not used for medical X-rays.
The energy spectrum of geiger tubes forbids that.

You may use either a ionisation chamber, or even better
a modern cadmium-zink-telluride sensor.

There are very stringent rules how to monitor medical equipment
and you better contact the manufacturers of your machines.

w.- Hide quoted text -

- Show quoted text -


w.

Thanks for the input. This is actually not for a medical device. FDA
does not just regulate medical devices but also for instance x-ray
cabinet systems. They have certain requirements that need to be met
for these kind of devices. One stipulation is that you cannot exceed
0.5mR/h 5cm from the cabinet. So I need a device that can verify this
reliably. If any of the cheap ($500) digital devices I mentioned can
do this then that's fine. Do they?

I'm still puzzled why there are such huge differences between
different devices ($500 vs $3000).

Since we use tube voltages similar to medical I am intersted in your
statement that a GM tube can't be used. Why is that?



I am going to take your word for it and assume you know what you are
doing. You ask why prices differ so much. I can think of may reasons,
boiled down to words such as MILSPEC, Marine and Medical. Those words
can make a world of difference in prices, usually up.

Of those, I think that Milspec is legitimate in this case. A counter of
that type must meet a pretty good shock.

On Tue, 24 Jul 2007 17:12:47 -0700, "
wrote:


........
Thanks for the input. This is actually not for a medical device. FDA
does not just regulate medical devices but also for instance x-ray
cabinet systems. They have certain requirements that need to be met
for these kind of devices. One stipulation is that you cannot exceed
0.5mR/h 5cm from the cabinet. So I need a device that can verify this
reliably. If any of the cheap ($500) digital devices I mentioned can
do this then that's fine. Do they?

I'm still puzzled why there are such huge differences between
different devices ($500 vs $3000).

Since we use tube voltages similar to medical I am intersted in your
statement that a GM tube can't be used. Why is that?

X-rays and gamma rays are essential the same thing.
X-rays are below 100keV, gamma rays range from 100 to 3000 keV
with some overlapping, do not take that as a sharp distinction.


Let us look at the energy spectrum of a typical medical device:
it ranges from 0 to 100 keV
http://www.amptek.com/medical.html

Now we look at the energy response of a geiger tube:
http://www.hps.org/hpspublications/articles/allard.html

The sensing threshold is about 60 keV, with a large overproportional
peak around 100 keV. For linearity over the energy range the tube has
to be linearized by wrapping it in lead and copper. Still there is no
response below 60 keV.

Geiger tubes are calibratet with Co60 radiation at 1,33 MeV
e.g. the LND712 which is used in the Gamma-Scout
http://www.lndinc.com/gm/alpha/712.htm

I cannot give a recommendation about what device to buy,
please join the Yahoo groups and put your question in there,
they are very knowledgeable people.


http://tech.groups.yahoo.com/group/CDV700CLUB/
http://tech.groups.yahoo.com/group/G...terEnthusiasts

w.

wrote:
On Jul 24, 12:04 pm, H. Wabnig .... .-- .- -... -. .. --.
@ .- --- -. DOT .- - wrote:

On Tue, 24 Jul 2007 09:37:25 -0700, "





I need of a Geiger counter to do radiation measurements of x-ray
equipment, cabinets, etc. Since these are numbers going into FDA
reports the counter has to be calibrated and meet all requirements for
the US. Something like a Bicron Surveyor would work quite well. I
would like to get a digital unit that could be used for long term
measurement (downloadable to a computer), though. So the requirements
a

1) Constant real-time measurement, i.e. not just one measurement for
one button click plus quick response time.
2) Beeper that beeps quicker and/or louder depending on the mR/h
measured.
3) Digital read-out for long term measurement.

There are two units I have seen:

1)http://www.gammascout.com/
2)http://www.imagesco.com/geiger/digit...r-counter.html

Any input is highly appreciated.

Geigers are not used for medical X-rays.
The energy spectrum of geiger tubes forbids that.

You may use either a ionisation chamber, or even better
a modern cadmium-zink-telluride sensor.

There are very stringent rules how to monitor medical equipment
and you better contact the manufacturers of your machines.

w.- Hide quoted text -

- Show quoted text -



w.

Thanks for the input. This is actually not for a medical device. FDA
does not just regulate medical devices but also for instance x-ray
cabinet systems. They have certain requirements that need to be met
for these kind of devices. One stipulation is that you cannot exceed
0.5mR/h 5cm from the cabinet. So I need a device that can verify this
reliably. If any of the cheap ($500) digital devices I mentioned can
do this then that's fine. Do they?

I'm still puzzled why there are such huge differences between
different devices ($500 vs $3000).

Since we use tube voltages similar to medical I am intersted in your
statement that a GM tube can't be used. Why is that?



You may need to employe a Certified Health Physicist (CHP) to make the
measurements and certify the results if FDA is involved.

Depending on your state regulations you may need to use a CHP approved
by your state Nuclear Regulation division, usually part of the state
health department.

GM tubes can be used at low X radiation levels but normal surveys are
done with ionisation chamber or solid state detector.


Hugh
Retired Nuc and not looking for work

On 7/25/07 12:32 AM, in article ,
"H. Wabnig" .... .-- .- -... -. .. --. @ .- --- -. DOT .- -
wrote:

On Tue, 24 Jul 2007 17:12:47 -0700, "
wrote:


........
Thanks for the input. This is actually not for a medical device. FDA
does not just regulate medical devices but also for instance x-ray
cabinet systems. They have certain requirements that need to be met
for these kind of devices. One stipulation is that you cannot exceed
0.5mR/h 5cm from the cabinet. So I need a device that can verify this
reliably. If any of the cheap ($500) digital devices I mentioned can
do this then that's fine. Do they?

I'm still puzzled why there are such huge differences between
different devices ($500 vs $3000).

Since we use tube voltages similar to medical I am intersted in your
statement that a GM tube can't be used. Why is that?

X-rays and gamma rays are essential the same thing.
X-rays are below 100keV, gamma rays range from 100 to 3000 keV
with some overlapping, do not take that as a sharp distinction.


Let us look at the energy spectrum of a typical medical device:
it ranges from 0 to 100 keV
http://www.amptek.com/medical.html

Now we look at the energy response of a geiger tube:
http://www.hps.org/hpspublications/articles/allard.html

The sensing threshold is about 60 keV, with a large overproportional
peak around 100 keV. For linearity over the energy range the tube has
to be linearized by wrapping it in lead and copper. Still there is no
response below 60 keV.

Geiger tubes are calibratet with Co60 radiation at 1,33 MeV
e.g. the LND712 which is used in the Gamma-Scout
http://www.lndinc.com/gm/alpha/712.htm

I cannot give a recommendation about what device to buy,
please join the Yahoo groups and put your question in there,
they are very knowledgeable people.


http://tech.groups.yahoo.com/group/CDV700CLUB/
http://tech.groups.yahoo.com/group/G...terEnthusiasts

w.
I do not know just what the FDA regulations aare, but a true Geiger counter
is not going to give a good exposure measurement. Every Geiger click will be
treated the same way whether it comes from a high or low energy photon. My
guess is that you want something like an ionization chamber in which high
energy photons can generate a number of counts roughly proportional to the
photon energy. Even an ion chamber will not tell you how tissue will react
because tissue will have a different composition than will air or whatever
gas fills the chamber.

The right way would be to use a proportional counter and a pulse height
analyzer. That way you will get a spectrum of the various energies in the
x-ray. That could be converted to an effective exposure in various ways by
weighing pulse heights in proportion to how they affect tissue or whatever
material is of interest.

Solid state radiation counters would probably be better to use rather than
gas counters.

Bill
--
Support the troops. Impeach Bush. Oh, I forgot about Cheney.