CA1066433A - Radiacmeter with flashing light readout - Google Patents
Radiacmeter with flashing light readoutInfo
- Publication number
- CA1066433A CA1066433A CA246,741A CA246741A CA1066433A CA 1066433 A CA1066433 A CA 1066433A CA 246741 A CA246741 A CA 246741A CA 1066433 A CA1066433 A CA 1066433A
- Authority
- CA
- Canada
- Prior art keywords
- dose rate
- light emitting
- radiation dose
- emitting diodes
- counting
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/16—Measuring radiation intensity
- G01T1/18—Measuring radiation intensity with counting-tube arrangements, e.g. with Geiger counters
Abstract
Abstract A low cost, hand held gamma radiation dose rate meter covering the dose rate range 0.1 to 100 R/hr, in which pulses from a Geiger-Mueller tube are amplified, counted and fed to a plurality of inter-connected light emitting diodes (LEDs) which flash at a rate proportional to the dose rate. The LEDs are interconnected so that only one can be on at any time thereby reducing peak current drain and making the dis-play simpler to read. The meter is contained in a pocket sized case which incorporates a battery and which may be moulded in plastic or die cast in metal.
Description
This invention ~elates to gamma radiation dose-rate meter (Radiac-meter) and more particularly to a simple, hand held, radiacmeter having a flashing light display.
This invention is related to the device described and claimed in A my copending Canadian application~ filed y ~ ~ch /~76 and which describes a radiacmeter with a null deflection readout system.
Radiacmeters are employed to determine gamma radiation dose-rate information in area6 where a radiation hazard exlsts or may exist. A
standard film badge dosimeter, which measures the cumulative radiation to which the individual wearer has been exposed, i8 an "after-the-event"
device in that the wearer is not aware of any excessive radiation at the time of expobure and it is only after the film has been developed that the hazard can be determined. Hence such a device is of no benefit to an individual or group of individuals who might be exposed to radiation levels which impose an immediate risk and whose freedom of action may, therefore, be limited to moving out of the contaminated area, or taking whatever steps are possible to find a more sheltered spot. It will be appreciated that, in peace time, exposure to low dose rates only is normally considered and such exposure poses no immediate risk to personnel and only a potential long term risk to those highly specialized personnel who are repeatedly exposed. In the event of nuclear war however, high dose rates that pose an immediate risk may well be encountered by a large number of individuals who are isolated from any control authority and it becomes essential to be able to determine rapidly that a hazard exists and decide whether evacua-tion or other measures are possible. A radiscmeter is therefore an essent-ial piece of equipment. This i8 essentially a "go - no go" sltuation and high accuracy of the equipment is not required. Small s$ze and ruggedness are, however, prime considerations, particularly for use in military survival packs or radiation kits issued to civil authorities or emergency measures organizations. For extensive civilian use low cost, reliability and ruggedne6s are of considerable importance and therefore plastic casings and encapsulation are considered highly desirable.
Many radiacmeters have been developed over the years but such -1- ~
instruments tend to be expensiye, heayy, bulky and xelatiYely fragile because they contain delicate moving parts 80 that they are not entirely suitable for use in the environmental sit^uations envisioned herein-above.
It is an ob~ect, therefore, of the present invention to provide a simple, lightweight, hand held radiacmeter which ig sufficiently rugged for use in military and civilian ~urvival situations, and which eliminates all moving parts except for an ON-OFF switch.
Thus, by one aspect of the present invention there is provided a self contained gamma radiation dose rate meter adapted to be hand held and comprising:
a substantially rigid, pocket sized casing which contains a power supply means;
a Geiger-Mueller tube, operatively connected to said power supply;
means for counting pulses transmitted by said Geiger-Mueller tube; and light means operatively connected to said counting means, providing a visual display proportional to said counted pulses which is viewable externally of said casing and which is indicative of a received gamma radiation dose rate.
The invention will be described in more detail hereinafter with reference to the drawings in which:
Flgure 1 is an isometric view, partially cut away, of a portable radiacmeter according to one aspect of this invention;
Figure 2 is a circuit diagram of the counting circuit employed in the radiacmeter of Figure l;
Figure 3 is a block diagram illustrating the timing of the flashing light readout of the radiacmeter of Figure l; and Figure 4, which is located on the sheet containing Figure 1, is a circuit diagram of the power supply circuit employed in the radiacmeter of Figure 1, Turning firstly to Figure 1, there is shown a portable lQ~6433 radiacmeter 1 which ha6 a lightweight cage, i5 approximately 4 1/8" x
This invention is related to the device described and claimed in A my copending Canadian application~ filed y ~ ~ch /~76 and which describes a radiacmeter with a null deflection readout system.
Radiacmeters are employed to determine gamma radiation dose-rate information in area6 where a radiation hazard exlsts or may exist. A
standard film badge dosimeter, which measures the cumulative radiation to which the individual wearer has been exposed, i8 an "after-the-event"
device in that the wearer is not aware of any excessive radiation at the time of expobure and it is only after the film has been developed that the hazard can be determined. Hence such a device is of no benefit to an individual or group of individuals who might be exposed to radiation levels which impose an immediate risk and whose freedom of action may, therefore, be limited to moving out of the contaminated area, or taking whatever steps are possible to find a more sheltered spot. It will be appreciated that, in peace time, exposure to low dose rates only is normally considered and such exposure poses no immediate risk to personnel and only a potential long term risk to those highly specialized personnel who are repeatedly exposed. In the event of nuclear war however, high dose rates that pose an immediate risk may well be encountered by a large number of individuals who are isolated from any control authority and it becomes essential to be able to determine rapidly that a hazard exists and decide whether evacua-tion or other measures are possible. A radiscmeter is therefore an essent-ial piece of equipment. This i8 essentially a "go - no go" sltuation and high accuracy of the equipment is not required. Small s$ze and ruggedness are, however, prime considerations, particularly for use in military survival packs or radiation kits issued to civil authorities or emergency measures organizations. For extensive civilian use low cost, reliability and ruggedne6s are of considerable importance and therefore plastic casings and encapsulation are considered highly desirable.
Many radiacmeters have been developed over the years but such -1- ~
instruments tend to be expensiye, heayy, bulky and xelatiYely fragile because they contain delicate moving parts 80 that they are not entirely suitable for use in the environmental sit^uations envisioned herein-above.
It is an ob~ect, therefore, of the present invention to provide a simple, lightweight, hand held radiacmeter which ig sufficiently rugged for use in military and civilian ~urvival situations, and which eliminates all moving parts except for an ON-OFF switch.
Thus, by one aspect of the present invention there is provided a self contained gamma radiation dose rate meter adapted to be hand held and comprising:
a substantially rigid, pocket sized casing which contains a power supply means;
a Geiger-Mueller tube, operatively connected to said power supply;
means for counting pulses transmitted by said Geiger-Mueller tube; and light means operatively connected to said counting means, providing a visual display proportional to said counted pulses which is viewable externally of said casing and which is indicative of a received gamma radiation dose rate.
The invention will be described in more detail hereinafter with reference to the drawings in which:
Flgure 1 is an isometric view, partially cut away, of a portable radiacmeter according to one aspect of this invention;
Figure 2 is a circuit diagram of the counting circuit employed in the radiacmeter of Figure l;
Figure 3 is a block diagram illustrating the timing of the flashing light readout of the radiacmeter of Figure l; and Figure 4, which is located on the sheet containing Figure 1, is a circuit diagram of the power supply circuit employed in the radiacmeter of Figure 1, Turning firstly to Figure 1, there is shown a portable lQ~6433 radiacmeter 1 which ha6 a lightweight cage, i5 approximately 4 1/8" x
2 1/2~' x 7t8" thick and which weighg between about 6 and 7 1/2 ounces including the battery. The cage 2 may be fabricated in either metal or plastic. A metal case, such as an aluminum alloy die-ca~ting, has the advantage of rigidity and ruggedness but is relatively more expensive to produce than the preferred thermopla8ticor thermosetting plastic moulded case. The case 2 is cloeed with an end cap 3 which incorporates an ON-OFF switch 4 and a battery compartment acces6 cap 5. A screw 6 may be provided to secure the cap 5 to case 2, or the cap may be designed to snap over case 2 and resiliently engage therewith in known manner.
The device i8 powered by a single penlight AA ~ize 1.5 V
battery 7 which is retained in a separate compartment 8 at one end of the case 2. At the opposite end of the case there is provided Geiger-Nueller (G-M) tube 9 which, if the preferred 18529 series tube is employed, is designed to Deasure do~e rates over the range 0.1 to 100 R/hr. A
flashing light readout 10, consisting of three different coloured light emitting diodes (LED) 11, 12,and 13, (Hewlett Packard 4684 series) is also provided in the case 2 80 that the LEDs are visible eYternally thereof. The LEDs flash at a rate proportional to the dose rate and provide a simple, easy-to-read indication of the dose rate level. An accurate readlng can be obtained by countlng the number of flashes during a predetenmined countlng period. Each counting perlod, which 18 preferably of about three second duration, is marked by a blank perlod of about one second during which time all three LEDs are off. Green LED 11 flashes once during each counting period per O.lR/hr of dose rate, orange LED 12 flashes once per lR/hr of dose rate and red LED 13 flashes once per lOR/hr as explalned in re tetail hereinunder the reference to Figure 3.
Circuit boards containing the GiM pulse amplification, counting, timing and power supply circuitry are unted in the caee between the battery compartment 8 and G~N tube 9.
An effective counting and ti~ing circuit as used in the device
The device i8 powered by a single penlight AA ~ize 1.5 V
battery 7 which is retained in a separate compartment 8 at one end of the case 2. At the opposite end of the case there is provided Geiger-Nueller (G-M) tube 9 which, if the preferred 18529 series tube is employed, is designed to Deasure do~e rates over the range 0.1 to 100 R/hr. A
flashing light readout 10, consisting of three different coloured light emitting diodes (LED) 11, 12,and 13, (Hewlett Packard 4684 series) is also provided in the case 2 80 that the LEDs are visible eYternally thereof. The LEDs flash at a rate proportional to the dose rate and provide a simple, easy-to-read indication of the dose rate level. An accurate readlng can be obtained by countlng the number of flashes during a predetenmined countlng period. Each counting perlod, which 18 preferably of about three second duration, is marked by a blank perlod of about one second during which time all three LEDs are off. Green LED 11 flashes once during each counting period per O.lR/hr of dose rate, orange LED 12 flashes once per lR/hr of dose rate and red LED 13 flashes once per lOR/hr as explalned in re tetail hereinunder the reference to Figure 3.
Circuit boards containing the GiM pulse amplification, counting, timing and power supply circuitry are unted in the caee between the battery compartment 8 and G~N tube 9.
An effective counting and ti~ing circuit as used in the device
-3-of Figure 1 is shown in pigure 2. pulses from the G-M tube 9 are ampli~ied and fed to four decade-counters Cl-C4 connected in series. The output of the second decade-counter is al60 fed into a NAND gate G5 inverted (G7) a~d into a constant current stage driving green LED 11.
Similarly the third counter stage drives the orange LED 12 and the fourth counter feed~ the red LED 13 drlven stage directly. The NAND
gates G5, G6 are connected ~o that only one of the three LEDs can be ON
at any time ao as to limit the peak current drain and also make the display simpler to read.
The operating voltages required, 500 V for the G-M tube and 3.5 V for the LEDs and counters, sre obtained from a dc-dc converter which is powered by a suitable sized 1.5 V dry cell. Conveniently a single pen light AA size 1.5 V battery will suffice as the instrument is not intended for continuous use and a zinc-carbon cell will provide for about 20 hours of operation. A manganese-al~aline cell will provide for at least 30 hours of operation. The circuit diagram of the converter, which i8 mounted on a suitable board and enclosed in case 2, as previous-ly indicated, is shown in Figure 4. Transistor Ql is a regulated swing-ing cho~e 08clllator. Any difference between the 3.5 V output voltage and the sener voltage is fed to the base of Q2which controlq the base drive of Qland the power supplied to the output circuits. The battery current drain varies from about 25 milliamps with no radiation to 35 milliamps with radiation at a battery voltage of 1.5 volts and 60 mllli-amps at 1 volt for an overscale reading i.e. more than ten red fla~hes per counting period.
In operation, the counting period is approximately three seconts and is controlled by a simple multivibrator Gl, G2 which drives a ~even stage rlpple counter C5. The last two stages of the ripple counter, fed to a NAND gate G3 and inverter G4, provide a reset pulse which inhibits the decade counters Cl, C2, C3, C4 for a time equal to one third of the counting period. At 0.1 R/hr a 18529 G-M tube is designed to emit about 33 pulses per
Similarly the third counter stage drives the orange LED 12 and the fourth counter feed~ the red LED 13 drlven stage directly. The NAND
gates G5, G6 are connected ~o that only one of the three LEDs can be ON
at any time ao as to limit the peak current drain and also make the display simpler to read.
The operating voltages required, 500 V for the G-M tube and 3.5 V for the LEDs and counters, sre obtained from a dc-dc converter which is powered by a suitable sized 1.5 V dry cell. Conveniently a single pen light AA size 1.5 V battery will suffice as the instrument is not intended for continuous use and a zinc-carbon cell will provide for about 20 hours of operation. A manganese-al~aline cell will provide for at least 30 hours of operation. The circuit diagram of the converter, which i8 mounted on a suitable board and enclosed in case 2, as previous-ly indicated, is shown in Figure 4. Transistor Ql is a regulated swing-ing cho~e 08clllator. Any difference between the 3.5 V output voltage and the sener voltage is fed to the base of Q2which controlq the base drive of Qland the power supplied to the output circuits. The battery current drain varies from about 25 milliamps with no radiation to 35 milliamps with radiation at a battery voltage of 1.5 volts and 60 mllli-amps at 1 volt for an overscale reading i.e. more than ten red fla~hes per counting period.
In operation, the counting period is approximately three seconts and is controlled by a simple multivibrator Gl, G2 which drives a ~even stage rlpple counter C5. The last two stages of the ripple counter, fed to a NAND gate G3 and inverter G4, provide a reset pulse which inhibits the decade counters Cl, C2, C3, C4 for a time equal to one third of the counting period. At 0.1 R/hr a 18529 G-M tube is designed to emit about 33 pulses per
-4-second or 100 pulses pex counting period. The output stage of each counter goes posltive after the eighth count and sta~s positive for two counts, thus the green LED 11 is on for the last 0.6 second of each countlng perlod at a 0.1 R/hr dose rate. Similarly the orange and red LEDs 12 and 13 are on for 0.6 second at lR/hr and lOR/hr respectively.
The device is calibrated by ad~u~ting the counting period to give two red flashes in a known field of 20 R/hr. Second figure accuracy can then be obtained by counting the flashe~ of the preceding (orange) stage.
For example, at 25 R/hr there will be two red flashes and five orange flashes after the second red flash and before the blank period. This is demonstrsted more clearly ln Figure 3. At the 25 R/hr level the G-M
tube pulses at a nominal 25,000 rate in the 3 second counting perlod.
There will therefore be approxi~ately 250 green LED pulses, 25 orange LED pulses and 2 red LED pulses. It will be appreciated that the green pulses will be blanked during orange or red pulses and that the orange pulse~ will be blanked during red pulses, 80 that the vi~ible pulses will be a- lndicated in Flgure 3. For the purposes of clarity only, 4 green pulses are illustrated between each orange pulse and lt will be appreciat-ed that, ln fact, there will be 8 such pulses. Following the counting period, the timing circuit provides that the reset period is approx1~tely one second and is signalled by a blank period during which all LEDs are extinguished.
In order to provide an indication that the instrument is working in the absence of a radiation field, the red LED is turned on for 1-2 seconds when the instrument is switched on. Thls is effected, as shown in Figure 2, by the CR circuit at the input of inverter 4~. As soon as the red test period has expired the instrument is ready for routine use and no further warm up period i- required.
It will, of cour~e, be appreciated that Dany difications to the circuitry and components may be made without departing fro~ the scope of this invention. For exaDple, although the Hewlett Packard 4684 _5_ series LED8 used iP tbe iPstX~oent shown in Fi~uxe 1 can be read easily at night ox in nor~al indoor or dull outdoor lighting conditions, they cannot be seen clearly in direct sunlight and it may be necessary to incorporate appropriate i'ilters into the visual sygtem or, in the alternative to employ larger, brighter LEDs guch a~ the Hewlett Packard 4658 series with attendent modificat~ons to the unit size of the instrument. Encapsulation of the components of the device contained within the case i8 also contemplated in order to ensure rigidity, water proofing ant elimination of long term corrosion and insulation break-down problems.
Replacing the 18529 G-M tube, or equivalent, with an 18503 G-M tube, or equivalent, enables this instrument to measure dose-rates over the range 0.1 to lOObR/h.
A solid state detector and amplifier could be used instead of the 18529 G-M tube and amplifier. This could pexmit four decades of dose-rate, 0.1 to l,OOOR/h, to be measured. Appropriate modificationc to the power supply and counting circuit would have to be made.
The device is calibrated by ad~u~ting the counting period to give two red flashes in a known field of 20 R/hr. Second figure accuracy can then be obtained by counting the flashe~ of the preceding (orange) stage.
For example, at 25 R/hr there will be two red flashes and five orange flashes after the second red flash and before the blank period. This is demonstrsted more clearly ln Figure 3. At the 25 R/hr level the G-M
tube pulses at a nominal 25,000 rate in the 3 second counting perlod.
There will therefore be approxi~ately 250 green LED pulses, 25 orange LED pulses and 2 red LED pulses. It will be appreciated that the green pulses will be blanked during orange or red pulses and that the orange pulse~ will be blanked during red pulses, 80 that the vi~ible pulses will be a- lndicated in Flgure 3. For the purposes of clarity only, 4 green pulses are illustrated between each orange pulse and lt will be appreciat-ed that, ln fact, there will be 8 such pulses. Following the counting period, the timing circuit provides that the reset period is approx1~tely one second and is signalled by a blank period during which all LEDs are extinguished.
In order to provide an indication that the instrument is working in the absence of a radiation field, the red LED is turned on for 1-2 seconds when the instrument is switched on. Thls is effected, as shown in Figure 2, by the CR circuit at the input of inverter 4~. As soon as the red test period has expired the instrument is ready for routine use and no further warm up period i- required.
It will, of cour~e, be appreciated that Dany difications to the circuitry and components may be made without departing fro~ the scope of this invention. For exaDple, although the Hewlett Packard 4684 _5_ series LED8 used iP tbe iPstX~oent shown in Fi~uxe 1 can be read easily at night ox in nor~al indoor or dull outdoor lighting conditions, they cannot be seen clearly in direct sunlight and it may be necessary to incorporate appropriate i'ilters into the visual sygtem or, in the alternative to employ larger, brighter LEDs guch a~ the Hewlett Packard 4658 series with attendent modificat~ons to the unit size of the instrument. Encapsulation of the components of the device contained within the case i8 also contemplated in order to ensure rigidity, water proofing ant elimination of long term corrosion and insulation break-down problems.
Replacing the 18529 G-M tube, or equivalent, with an 18503 G-M tube, or equivalent, enables this instrument to measure dose-rates over the range 0.1 to lOObR/h.
A solid state detector and amplifier could be used instead of the 18529 G-M tube and amplifier. This could pexmit four decades of dose-rate, 0.1 to l,OOOR/h, to be measured. Appropriate modificationc to the power supply and counting circuit would have to be made.
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A hand held self contained gamma radiation dose rate meter comprising:
a substantially rigid, pocket sized casing which contains:
(a) a power supply means;
(b) a Geiger-Mueller tube, operatively connected to said power supply;
(c) means for counting pulses transmitted by said Geiger-Mueller tube in the presence of ionizing radiations over a preselected time period; and (d) a plurality of light emitting diodes operatively interconnected with said counting means, each of which is adapted to flash at a different rate proportional to said counted pulses over a predetermined counting period thereby providing a substantially continuous visual display of a received dose rate.
a substantially rigid, pocket sized casing which contains:
(a) a power supply means;
(b) a Geiger-Mueller tube, operatively connected to said power supply;
(c) means for counting pulses transmitted by said Geiger-Mueller tube in the presence of ionizing radiations over a preselected time period; and (d) a plurality of light emitting diodes operatively interconnected with said counting means, each of which is adapted to flash at a different rate proportional to said counted pulses over a predetermined counting period thereby providing a substantially continuous visual display of a received dose rate.
2. A radiation dose rate meter as claimed in claim 1 and including (e) means for amplifying said pulses transmitted from said Geiger-Mueller tube interposed between said Geiger-Mueller tube and said counting means.
3. A radiation dose rate meter as claimed in claim 1 which includes coloured light emitting diodes each of which flashes at a rate proportional to a decade of dose rate.
4. A radiation dose rate meter as claimed in claim 3 including timing delay means for effecting a blank period, between each successive counting period, during which all said light emitting diodes are off.
5. A radiation dose rate meter as claimed in claim 1 including means for actuating one of said light emitting diodes for a short period of time in the absence of a radiation field, thereby providing an indicator of operability.
6. A radiation dose rate meter as claimed in claim 3 including means to prevent flashing of two of said light emitting diodes when a third said light emitting diode is flashing.
7. A radiation dose rate meter as claimed in claim 3 having three differently coloured light emitting diodes.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA246,741A CA1066433A (en) | 1976-02-27 | 1976-02-27 | Radiacmeter with flashing light readout |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA246,741A CA1066433A (en) | 1976-02-27 | 1976-02-27 | Radiacmeter with flashing light readout |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1066433A true CA1066433A (en) | 1979-11-13 |
Family
ID=4105336
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA246,741A Expired CA1066433A (en) | 1976-02-27 | 1976-02-27 | Radiacmeter with flashing light readout |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1066433A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4642466A (en) * | 1985-03-05 | 1987-02-10 | The United States Of America As Represented By The United States Department Of Energy | Fast counting electronics for neutron coincidence counting |
| WO1990001709A1 (en) * | 1988-08-08 | 1990-02-22 | Österreichisches Forschungszentrum Seibersdorf Ges.M.B.H. | Radiation measuring device |
| US5045700A (en) * | 1989-08-29 | 1991-09-03 | Crowson Robert H | Headgear-mounted indicator for ionizing radiation |
| US5258926A (en) * | 1988-08-08 | 1993-11-02 | Osterreichesches Forschungszentrum Seibersdorf Gmbh | Method of measuring radiation for a radiation measuring device |
-
1976
- 1976-02-27 CA CA246,741A patent/CA1066433A/en not_active Expired
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4642466A (en) * | 1985-03-05 | 1987-02-10 | The United States Of America As Represented By The United States Department Of Energy | Fast counting electronics for neutron coincidence counting |
| WO1990001709A1 (en) * | 1988-08-08 | 1990-02-22 | Österreichisches Forschungszentrum Seibersdorf Ges.M.B.H. | Radiation measuring device |
| US5258926A (en) * | 1988-08-08 | 1993-11-02 | Osterreichesches Forschungszentrum Seibersdorf Gmbh | Method of measuring radiation for a radiation measuring device |
| US5045700A (en) * | 1989-08-29 | 1991-09-03 | Crowson Robert H | Headgear-mounted indicator for ionizing radiation |
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