Radiant energy – Geological testing or irradiation – Well testing apparatus and methods
Patent
1994-08-16
1995-10-24
Willis, Davis L.
Radiant energy
Geological testing or irradiation
Well testing apparatus and methods
250262, G01V 504, G01V 500
Patent
active
054612306
ABSTRACT:
A method and apparatus for providing temperature compensation in gamma radiation detectors used in measurement-while-drilling applications in oil and gas exploration. During the initial calibration of a gamma radiation detector, a source of radiation in the form of Americium 241 provides gamma radiation narrowly centered at 60 KeV. The variation in the output signal of the detector as a function of temperature is then determined by placing the detector in close proximity to the radiation source while monitoring the variation in the magnitude of the output pulses as a function of temperature. The detector includes a temperature compensation circuit that generates a threshold voltage whose magnitude corresponds to the desired threshold energy of gamma radiation. The temperature compensation circuit uses a temperature sensor to vary the magnitude of the threshold voltage as a function of the operating temperature of the detector. The variation in the threshold voltage compensates for attenuation of the high frequency output signal of the detector as a function of the operating temperature by comparing the magnitude of the threshold voltage with the magnitude of a filtered output signal. A high count signal is produced whenever the energy level of the detected gamma radiation is equal to or greater than the threshold energy value. The high count signal indicates to other circuitry that the detected gamma radiation is to be counted.
REFERENCES:
patent: 3916685 (1975-11-01), Paap et al.
patent: 4220851 (1980-09-01), Whatley
patent: 4346590 (1982-08-01), Brown
patent: 5272336 (1993-12-01), Moake
Halliburton Company
Hanig Richard
Willis Davis L.
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