I is for... Isotope. The geiger-counter / meter page.

some radiation detector / geiger-meter stuff ....

This is my old, Now sold Radiac 2. This was a nice old gamma device.
It's major disadvantages were the need for four batteries. Two of them were
high voltage special types, and that it responds to gamma only. I had this for a
few years and as I could not get the batteries for it. I never got it going. It's
really more for the cold-war era radiation atomic - bomb nuts really. Made here
in the UK by E.K.Cole Ltd. I picked this one up at a military show here in Kent.

The Thorn radiac unit. Rather nice and reminds me of the German made radiac meters
of the 80's. But again the need for a button-cell and a high voltage battery made this
device a novelty rather than a practical geiger meter for my needs. So again this unit
has now been sold. You can see from the label that it has it's own internal radiation
source so the unit can be self-calibrated! This was no-doubt removed before the radiac
was released to the public. It would have been a rather nice unit had it used more common
batteries, as it is a gamma and beta detector.

This is My Tube Test Box. It's small and portable. It's got a griffen
and george inverter unit in the case, along with a comparator, a 555 based
oscillator, and pizzo-sounder. All battery-powered from 4 AA cells. On the
front panel are a couple of sockets so I can attach tubes from my other units
voltage control to set the tube working voltage from 200-450V. a sounder and
on-off switch. At some point in the future I will find a small meter and build
some circuitry to drive it. But for now it's a quick and easy way of checking
un-known tubes. Shown in the pictures here with a mulard MX168 Beta-Gamma tube.

This is a Nuclear Enterprises Ltd. Contamination Meter 95/0339-1/6
I picked this rather cool UK made radioactivity contamination meter up on an
internet auction site. These are not to common. and this one needed just
a little minor TLC and some fresh batteries before it came back to life. It
rather nicely uses two D-Cells and the current drain on them is very low so
they will last ages! the connection between the main unit and the probe is co-ax
and BNC connectors. Not ideal given the high voltages it uses. The Beta probe
Nuclear Enterprises Ltd Part number BP3/4 uses an octal-based detector tube
made by Centronic (a type B12H). This tube has a working voltage of 350V
The main unit can be adjusted on the front panel to produce from 300-1300V
so this combination of meter and probe are rather versatile. I have connected
the probe to my universal test-jig (see above) too and it works very well.

See here for a video of it up and running. I switch it on to Battery-test, then
to EHT and set the volts to about 375V. then to scintillation and show it working
with a rather active source I use for testing. it reads 150counts/second on gamma
and 3000counts/second on beta. How cool is that. Copy/Paste the Link to a video below.

The SV500 type NATO radiac. this one is marked up in Dutch? I think? I don't
understand the language... It came in for repair. A dead High-Voltage section.
This is a good radiation meter and is one of my favorites

A recent one in. this is another SV500 type NATO radiac / geiger counter. This
unit is marked-up in English. It arrived from Germany complete with the user manual
lovely and clean and in working order. It has intermittant connections on the
earphone and battery lead. but these can both be repaired or replaced. The case
of this unit is larger than the SV500 above. This version has a second tube
for detecting Beta and Gamma radiation. As you can see from the kit-layout
above. The battery pack and gamma tube can be removed from the main-unit. This
is the same with all of this series of radiation meter. The battery can be
tucked somewhere warm if you are working in acctic conditions. and connected bu the
cable. Also either the gamma or the Beta/Gamma tube can be attached remotely
making this a rather useful device. I have made a video of this unit working
and as you can see it's rather sensitive over 5000c/s beta. Link to a video below.

Arrived here from a good friend in Derbyshire. This is a "Mini-monitor" G-M Meter
Type 510. Made by Mini Instruments in Essex here in the UK. The meter uses the ZP1481
tube from Centronic which is a compatible/replacement for the Mulard MX168 Beta-Gamma tube.
The tube is contained in an aluminium tube of about 1 1/2 inches diameter (about 37mm)
which can be clipped to the top of the meter. Sensitive to Beta and Gamma, and close-up
Alpha particles. and very sensitive even with the brass tube-cap in place. A nice small
instrument! According to the information on the rear of this unit. It can also be used
with the Centronic B6H. and Mullard MX123 and MX180 tubes.

A couple of minor complaints with this GM Meter are :-
1/ It needs 12x AA-Type batteries (a total of 18v DC).
2/ The tube and instrument are hard-wired (no connectors between them).

At some stage, possibly when the 12 batteries I have put in there are flat, I will try
the unit on two smaller and cheaper 9v batteries. The current drain of this instrument
in very low so I can see no problems other than a shorter period of operation between
battery changes. Also I may retro-fit connectors on the meter and the tube assembly
to allow other tubes to be used more easily.
The first picture above shows the unit responding to a Sr 90 source with the brass
tube cap in place. Without the cap the meter reads way over full-scale >2000 c/sec.