[ Pobierz całość w formacie PDF ]
and ³ particles. Fortunately most radio- connected the cathode strap supplied drilled in the board. The cathode con-
active elements emit all three radiations
so the ZP1310 is entirely adequate for
most purposes.
Construction
The construction is reasonably sim-
ple, since it is mostly confined to the
printed circuit board. Start by mounting
the resistors and capacitors on the pc
board. Then mount the transistors,
diodes and power transformer. Be sure
the transistors, diodes and electrolytic
capacitors are connected the correct
way around. The pc board has provi-
sion to drive a 50 uA meter movement
although I did not use this facility when
building the prototype. The biggest
problem is one of calibration. The meter
is useless unless one has access to a cal-
©
ibrated reference instrument. For most
purposes it is sufficient to use the click
rate as an indication as to how radioac-
Geotech Page 3
ETI: How To Build Gold & Treasure Detectors, 1981 Copyright
Murray/Modern Magazines, reproduce for personal use only
nection to the tube is made by soldering
the cathode strap onto the small pc
board. As with the ZP1310 do not sol-
der directly to the anode of the tube.
Use an anode connector if it is supplied
or a socket pin from a 9-pin valve
socket.
Once the board is completed it can be
mounted in a suitable chassis. I used a
Horwood type 34/10/DS, in which
everything fits quite nicely. The circuit
operates from six to nine volts and the
battery used in the prototype was an
Eveready type 276-P. This is a nine volt
battery and is best mounted using a
bracket of bent-up aluminium. The cir-
cuit pulls around 50 mA, so whatever
battery you choose make sure it is capa-
ble of delivering this amount of current.
Powering up
Before applying power to the circuit
check the pc board layout. Make sure
that all polarised components have been
mounted on the pc board correctly.
Make a special check of the two 10 V
zener diodes. These regulate the volt-
age that is applied to the tube so it is
important that they are inserted cor-
rectly. If all is well connect the battery
and measure the voltage at point X on
©
the pc board. This is the output of the
voltage multiplier and the voltage at this
point should be between 550 V and 650
V.
The moment the unit is turned on it
THE GEIGER MULLER TUBE
the anode and the cathode,
This consists of a metal tube
anode being positive with
or cylinder, hermetically sealed
respect to the cathode.
and filled with a gas at less
As the voltage between the
than atmospheric pressure. If
electrodes is increased, the
the tube is intended for the
tube goes through three
detection of alpha particles (as
well as beta and gamma radia- phases: if the voltage is lower
than a particular value, the gas
tions), it will be constructed with
in the tube will not be ionised
an end window , as illustrated
and no current will flow. Above
here. Since alpha particles
this particular voltage (the
have so little penetrating ability
striking voltage), the gas ion-
the window must be extremely
When a particle enters the and electrons. Each avalanche
thin. Thus, the windows are dif- ises and a small current flows
tube operating in its plateau is registered as a momentary
continuously through the tube.
ficult to manufacture and are
region, it ionises the gas fur- increase in the current through
This is the phase in which the
fragile.
ther and the ions produced are the tube. This current pulse can
tube is operated referred to as
Geiger tubes constructed to
accelerated towards the cath- be detected as a voltage pulse
the plateau region . If the volt-
detect only beta and gamma
ode, electrons towards the across a resistor connected in
age is increased even further
radiations do not have an end
anode. These moving ions series with the tube. If the volt-
window, otherwise construc- still the tube will enter the third
cause further ionisations and age pulse is coupled to a
phase that of arc discharge
tion is similar.
an avalanche of ions (and elec- sensitive audio amplifier driv-
between the anode and cath-
In the centre of the tube is a
trons) occurs. ing a loudspeaker, a sharp
wire ANODE. The metal cylin- ode. If the tube is allowed to
When the tube is operated in click will be heard. Each click
operate in these conditions it
der itself serves as a
its plateau region a single parti- from the geiger counter repre-
will almost certainly be
CATHODE. In operation, a high
cle of radiation will cause an sents the incidence of a particle
damaged.
voltage is connected between
avalanche of millions of ions on the GM tube.
Geotech Page 4
ETI: How To Build Gold & Treasure Detectors, 1981 Copyright
Murray/Modern Magazines, reproduce for personal use only
will start to detect
background radiation.
The unit will click
once every couple of
seconds. This back-
ground radiation is
caused mainly by cos-
mic radiation.
Some older watches
used small amounts of
radioactive isotopes to
activate the luminous
dial. Even if the dial
has long since lost its
luminosity it will still
be radioactive. If this
watch dial is brought
near the geiger counter
the count rate will
increase significantly.
©
Geotech Page 5
ETI: How To Build Gold & Treasure Detectors, 1981 Copyright
Murray/Modern Magazines, reproduce for personal use only [ Pobierz całość w formacie PDF ]
zanotowane.pl doc.pisz.pl pdf.pisz.pl ocenkijessi.opx.pl
and ³ particles. Fortunately most radio- connected the cathode strap supplied drilled in the board. The cathode con-
active elements emit all three radiations
so the ZP1310 is entirely adequate for
most purposes.
Construction
The construction is reasonably sim-
ple, since it is mostly confined to the
printed circuit board. Start by mounting
the resistors and capacitors on the pc
board. Then mount the transistors,
diodes and power transformer. Be sure
the transistors, diodes and electrolytic
capacitors are connected the correct
way around. The pc board has provi-
sion to drive a 50 uA meter movement
although I did not use this facility when
building the prototype. The biggest
problem is one of calibration. The meter
is useless unless one has access to a cal-
©
ibrated reference instrument. For most
purposes it is sufficient to use the click
rate as an indication as to how radioac-
Geotech Page 3
ETI: How To Build Gold & Treasure Detectors, 1981 Copyright
Murray/Modern Magazines, reproduce for personal use only
nection to the tube is made by soldering
the cathode strap onto the small pc
board. As with the ZP1310 do not sol-
der directly to the anode of the tube.
Use an anode connector if it is supplied
or a socket pin from a 9-pin valve
socket.
Once the board is completed it can be
mounted in a suitable chassis. I used a
Horwood type 34/10/DS, in which
everything fits quite nicely. The circuit
operates from six to nine volts and the
battery used in the prototype was an
Eveready type 276-P. This is a nine volt
battery and is best mounted using a
bracket of bent-up aluminium. The cir-
cuit pulls around 50 mA, so whatever
battery you choose make sure it is capa-
ble of delivering this amount of current.
Powering up
Before applying power to the circuit
check the pc board layout. Make sure
that all polarised components have been
mounted on the pc board correctly.
Make a special check of the two 10 V
zener diodes. These regulate the volt-
age that is applied to the tube so it is
important that they are inserted cor-
rectly. If all is well connect the battery
and measure the voltage at point X on
©
the pc board. This is the output of the
voltage multiplier and the voltage at this
point should be between 550 V and 650
V.
The moment the unit is turned on it
THE GEIGER MULLER TUBE
the anode and the cathode,
This consists of a metal tube
anode being positive with
or cylinder, hermetically sealed
respect to the cathode.
and filled with a gas at less
As the voltage between the
than atmospheric pressure. If
electrodes is increased, the
the tube is intended for the
tube goes through three
detection of alpha particles (as
well as beta and gamma radia- phases: if the voltage is lower
than a particular value, the gas
tions), it will be constructed with
in the tube will not be ionised
an end window , as illustrated
and no current will flow. Above
here. Since alpha particles
this particular voltage (the
have so little penetrating ability
striking voltage), the gas ion-
the window must be extremely
When a particle enters the and electrons. Each avalanche
thin. Thus, the windows are dif- ises and a small current flows
tube operating in its plateau is registered as a momentary
continuously through the tube.
ficult to manufacture and are
region, it ionises the gas fur- increase in the current through
This is the phase in which the
fragile.
ther and the ions produced are the tube. This current pulse can
tube is operated referred to as
Geiger tubes constructed to
accelerated towards the cath- be detected as a voltage pulse
the plateau region . If the volt-
detect only beta and gamma
ode, electrons towards the across a resistor connected in
age is increased even further
radiations do not have an end
anode. These moving ions series with the tube. If the volt-
window, otherwise construc- still the tube will enter the third
cause further ionisations and age pulse is coupled to a
phase that of arc discharge
tion is similar.
an avalanche of ions (and elec- sensitive audio amplifier driv-
between the anode and cath-
In the centre of the tube is a
trons) occurs. ing a loudspeaker, a sharp
wire ANODE. The metal cylin- ode. If the tube is allowed to
When the tube is operated in click will be heard. Each click
operate in these conditions it
der itself serves as a
its plateau region a single parti- from the geiger counter repre-
will almost certainly be
CATHODE. In operation, a high
cle of radiation will cause an sents the incidence of a particle
damaged.
voltage is connected between
avalanche of millions of ions on the GM tube.
Geotech Page 4
ETI: How To Build Gold & Treasure Detectors, 1981 Copyright
Murray/Modern Magazines, reproduce for personal use only
will start to detect
background radiation.
The unit will click
once every couple of
seconds. This back-
ground radiation is
caused mainly by cos-
mic radiation.
Some older watches
used small amounts of
radioactive isotopes to
activate the luminous
dial. Even if the dial
has long since lost its
luminosity it will still
be radioactive. If this
watch dial is brought
near the geiger counter
the count rate will
increase significantly.
©
Geotech Page 5
ETI: How To Build Gold & Treasure Detectors, 1981 Copyright
Murray/Modern Magazines, reproduce for personal use only [ Pobierz całość w formacie PDF ]