Improve Calibration Accuracy Research Articles

A theoretical investigation of calibration methods for radwaste radioactivity detection systems

The three-dimensional point-kernel computer code QAD-CGGP is used to calibrate the Q2 detection system proposed as the detection system for measuring uncollided photon fluence rate from low-level radwaste at the Kuosheng and Maanshan Nuclear Power Plants in Taiwan. The calibration drum in the Q2 detection system was originally divided into seven concentric regions of equal volume. This was replaced by seven thin source tubes to eliminate storage problems associated with the uniformly distributed sources for each concentric region, and was found that the position of the source tube in the outermost region of the drum can significantly affect calibration accuracy. This phenomenon becomes more serious for highly attenuated radwaste such as sand. Although proper adjustment of the source tube position in the outermost region improves calibration accuracy, especially for highly attenuated radwaste, the new source tube position is too close to the surface of the drum and can increase calibration inaccuracy when the materials in the source tube and in the rest of the drum are different. We propose an improved method that divides the calibration drum into three region sources. Appropriate arrangement of the source tube positions within these regions was found to improve calibration accuracy, simplify calibration procedures, and save calibration time.

Segment based camera calibration

The basic idea of calibrating a camera system in previous approaches is to determine camera parameters by using a set of known 3D points as calibration reference. In this paper, we present a method of camera calibration in which camera parameters are determined by a set of 3D lines. A set of constraints is derived on camera parameters in terms of perspective line mapping. From these constraints, the same perspective transformation matrix as that for point mapping can be computed linearly. The minimum number of calibration lines is 6. This result generalizes that of Liu, Huang and Faugeras[12] for camera location determination in which at least 8 line correspondences are required for linear computation of camera location. Since line segments in an image can be located easily and more accurately than points, the use of lines as calibration reference tends to ease the computation in image preprocessing and to improve calibration accuracy. Experimental results on the calibration along with stereo reconstruction are reported.

Impedance characteristics of transducers and reciprocity calibration

This paper investigates impedance characteristics of electrodynamic-type and piezoelectric-type transducers. The inherent relation between mechanical impedance of a mass load and electrical impedance of the transducing element of transducers is revealed. The substance of reciprocity calibration is just to utilize the impedance inversive property of both types of transducers so that one can determine the mechanical quantities (force and velocity) by measuring electrical quantities, which can be measured conveniently and accurately. According to the theory, for high-frequency calibration, mass values in the reciprocity calibration formulas should be replaced by their equivalent masses rather than static mass values, because the mechanical impedances of mass loads will be remarkably changed due to the stress wave effect. Making the correction can improve calibration accuracy by about one-half order of magnitude.

Effects of body size on potassium-40 measurement in the whole body counter (tilt-chair technique).

The precision of 40K determination in man by the tilt-chair technique is compromised by geometrical and self absorption factors. In an attempt to improve calibration accuracy simultaneous measurements of 40K and total body water (deuterium dilution) were made in 50 subjects of widely varying body size. The results show that neither height nor weight per se affects the observed body ratio of 40K/H2O, and that the principal systematic error concerns the relative fat content of the subject. Correction of the observed 40K values for this factor improves the accuracy of the measurement.

Calibration of the Donaldson Colorimeter

The standard procedure of calibrating the Donaldson six-primary colorimeter is reviewed critically and some sources of systematic errors which might affect the accuracy of the calibration are discussed. In particular, the effect of the temperature variations of the primary filters and the nonuniform spectral transmittances of certain optical components of the instrument are studied. A way is described which leads to an improved calibration accuracy.

Electroencephalographic technique from an engineer's point of view

A fairly recent medical usage of electronic equipment is in the recording of the electrical activity of the brain. High-gain, high-fidelity amplifying equipment is used to record 50-microvolt, 2- to 40-cycle-per-second impulses from the brain. A brief summary of interpretation is made, particularly in reference to artifact. A new type of electrode is described which fulfills the criteria for good leads. Suggestions on the improvement of existing equipment are made, such as to improve calibration accuracy and recorder performance.