Abstract: The present invention relates to an improvement in a nuclear measuring gauge for measuring the composition of a hydrogen containing material by counting neutrons which are thermalized by the presence of the hydrogen in the material. The present invention is based upon the recognition that in measuring samples, such as hot asphalt, with such a gauge, the error which is introduced by temperature variations in a sample is a function of not only the temperature of the sample but also its hydrogen content. In accordance with the present invention, this inaccuracy is compensated for by applying to the measurement a correction factor which is a function of both the temperature of the sample and its hydrogen content.

Abstract: The present invention provides a method and system which is useful on instruments requiring experimentally determined calibration curves by which calibration data can be transferred to a plurality of field gauges, thereby avoiding the necessity of individually calibrating each gauge each time calibration is necessary. The field gauges are initially cross related to a master gauge. At a later time when a new calibration is necessary, the master gauge is calibrated using carefully prepared samples of a test material. Using the experimentally derived calibration curves with the cross relation data provides calibration data for the field gauges.

Abstract: Nuclear density gauges of the type having a gamma source which is positionable at several different source depth positions with respect to a detector are calibrated in an efficient and advantageous manner by a calibration procedure which reduces the number of experimental counts which must be taken. In accordance with the present invention, a single calibration block is employed and counts are taken at one or more source depth positions on the block. Through the use of historically derived relationships between the count rate obtained from the calibration block to the count rates obtained from at least two different calibration blocks of other known densities, the expected calibration counting rates for the other blocks can be obtained. These calculated counting rates are then used along with the experimentally determined counting rate to obtain the calibration constants for the gauge.

Abstract: The nuclear moisture-density gauge of the present invention employs a low activity neutron radiation source and a low activity gamma radiation source. In order to achieve more accurate density measurements at the relatively low count rates which results from the use of a low activity gamma source, the present invention is provided with means for generating a correction signal which is a function of the moisture content of the test material and which represents the amount of gamma radiation emitted from the test material resulting from the neutron capture reaction due to the presence of neutron capture elements, such as hydrogen, present in the test material. This correction signal is applied to the uncorrected density signal obtained from the gauge to thereby obtain a corrected density measurement which is unaffected by background gamma radiation caused by the presence of neutron capture elements in the test material.

Abstract: The present invention provides an apparatus for detecting the depth position of the source rod of a portable nuclear measuring gauge having a housing with the elongate source rod extending vertically therethrough and mounted for vertical sliding movement to various depth positions. The apparatus comprises an elongate variable resistance element extending axially parallel to said source rod, means for slideably engaging the elongate variable resistance element as the source rod is moved to various depth positions so as to vary the resistance of said variable resistance element, and means electrically connected to said variable resistance element for sensing the changes in resistance thereof and converting such changes into an indication of the depth position of the source rod.

Abstract: The remaining battery life of a battery powered device is predicted by monitoring the immediate past history of battery life and employing this immediate past history as a basis for subsequent predictions of the useful life of the battery. By this approach, the present invention is able to take into account the deterioration of battery life which occurs during the life-time of a rechargeable battery.

Abstract: The present invention provides a nuclear radiation backscatter gauge and method by which an accurate determination of the density of a test material can be made, even though the test material may have surface irregularities or voids which would otherwise contribute significant error to the density measurement. The invention is based upon the use of a nuclear density gauge which is specially designed for measuring thin layers, and which is characterized by having a source and at least two separate detector systems mounted in geometrically differing relationships with respect to the source. Through the use of this type of gauge, in combination with a pad or block of known thickness and density, a measurement is made of the density of a top zone of a predetermined thickness which is greater than the thickness of the block and which thus encompasses not only the block but also an upper portion of the underlying material where the surface voids and irregularities exists.

Abstract: The present invention provides a nuclear radiation backscatter gauge which is capable of directly measuring the density of a thin top layer of material from a composite material comprised of the relatively thin top layer of material applied over an underlying base material. The gauge includes a nuclear radiation source and two radiation detector means so positioned with respect to the source as to form two geometrically differing source-to-detector relationships. A signal processing circuit responds to detected radiation from the two detector means to generate respective signals D.sub.G1 and D.sub.G2 representative of the components densities of the top and base layers as measured by the detector means. The density D.sub.T of the thin top layer is then determined by a signal processing means from the relationship ##EQU1## wherein k.sub.1 and k.sub.2 are empirically derived instrument constants.

Abstract: A method for recalibrating nuclear density gauges comprises the taking of count rate data from two calibration blocks, preferably magnesium and aluminum, for each source depth position of the gauge and thereafter computing new values for constants A and C in a standard working exponential equation for the gauge:CR=A exp (-BD)-C.

Abstract: An area is surveyed for variation in a physical characteristic or property which is effective for modifying nuclear radiation of a predetermined type through the use of an apparatus and in accordance with a method in which the modifying characteristic is measured by applying nuclear radiation while generating a signal representative of the measured characteristic, the generated signal is registered in the programmable memory device, the steps of measuring while generating and registering are thereafter repeated, and the information gathered is transmitted for retrieval and processing at a remote location.

Abstract: A method, and a nuclear radiation gauge, for surveying a roof for moisture in which a thermal neutron gauge is positioned at a predetermined location on a roof, the signal representative of the hydrogen content of the roof at that location is generated and registered in a programmable memory device, and the gauge is then moved to a succession of predetermined locations arranged in a predetermined array on the roof while repeating the steps of generating and registering signals at each location.

Abstract: A radiation scatter gauge includes multiple detector locations for developing separate and independent sets of data from which multiple physical characteristics of a thin material and underlying substrate may be determined. In an illustrated embodiment, the apparatus and method of the invention are directed to determining characteristics of resurfaced pavement by nondestructive testing. More particularly, the density and thickness of a thin asphalt overlay and the density of the underlying pavement may be determined.

Abstract: A hydrophobic standard for calibrating nuclear radiation moisture gauges. In accordance with this invention, each standard has physical characteristics and dimensions effective for representing to a nuclear gauge undergoing calibration an infinite mass of homogeneous hydrogen content. Calibration standards are disclosed which are suitable for use with surface gauges and with depth gauges.