Boots – shoes – and leggings
Patent
1991-04-03
1993-11-02
Harvey, Jack B.
Boots, shoes, and leggings
G01T 118
Patent
active
052589269
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of measuring radiation for a radiation measurement device with at least two Geiger-Muller counter tubes of different sensitivity, high voltage supply means in connection with each of said Geiger-Muller counter tubes and microprocessor means including program storage means and random access memory means capable of switching between said Geiger-Muller tubes based on said radiation intensity whereby at least one Geiger-Muller counter tube generates pulses wherein an actual integration interval is determined by a measurement algorithm.
2. Description of Prior Art
Various radiation measuring devices, both stationary and portable, are known, including those employing a Geiger-Muller counter. In Geiger-Muller counters, a gas filled chamber is employed in which is incorporated two electrodes. The ionization produced by radiation dissipates part of all of its energy by generating electron ion pairs. A count is registered each time a pulse of voltage exceeds a minimum value established. European Patent Publication No. 0 151 880 refers to a particular radiation detector using Geiger-Muller tubes, in which instead of counting radiation pulses the elapsed time interval to the incident of the first strike is determined. This is done to avoid negative influences of dead time and thus to provide a linear read-out. Furthermore, this document discloses the possibility of switching between two different detectors based on the radiation intensity. IEEE Transactions on Nuclear Science, Vol. NS-34, No. 1, Feb. 1987 (New York, NY, U.S.A); H. C. Staley et al.: "Radiation Detection Algorithm for a Portable Survey Instrument", pp. 619 -621, discloses detectors counting impulses over a predetermined time interval.
Heretofore, different measurement instrument devices were required for different types of radiation and different intensity levels. For example, a device for measuring low level environmental background radiation would not be suitable for measuring high dose rates.
SUMMARY OF THE INVENTION
It is a principal object and purpose of the present invention to provide an accurate method of measuring radiation with a radiation measurement device which covers an extremely wide operating range utilizing two Geiger-Muller tubes with a central microprocessor which automatically switches between the two.
According to the invention, the aforementioned method comprises setting the actual integration interval to the value of the previous integration interval or to a fixed value at start up; retrieving a check interval from the actual integration interval, by taking the square root of the actual integration interval and adding a constant; calculating the average of the Geiger-Muller counter pulses for the check interval of time; selecting a specific measuring range and specific values for parameters of the algorithm according to the average, said values being the upper and the lower limit for the actual integration interval and the upper and lower limit for the allowed statistical fluctuation of the radiation intensity in said measuring range; comparing the actual integration interval to the upper limit; determining whether the actual integration interval falls below or above the upper limit for the actual integration interval; setting the integration interval to the upper limit if it was above the limit and letting the integration interval remain unchanged if it was less than or equal to the limit; calculating the average value of the counted Geiger-Muller pulses during the actual integration interval; determining a tolerance band by weighting said average value with the given values of the upper and lower limit of the statistical fluctuation; using the average value of the counter pulses for calculation of the dose rate if the average falls within said tolerance band and incrementing the actual integration interval or shortening the actual integration interval if the average falls outside the tolerance band and using said shortened integra
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"Radiation Detection Algorithm for a Portable Survey Instrument," IEEE Transactions on Nuclear Science, vol. NS-34, No. 1, of Feb. 1987, pp. 619-621.
Duftschmid Klaus E.
Norbert Bock
Wolfgang Klosch
Harvey Jack B.
Osterreichesches Forschungszentrum Seibersdorf GmbH
Ramirez Ellis B.
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