Ales Zikmund

Precise Calibration Method for Triaxial Magnetometers Not Requiring Earth’s Field Compensation

A calibration procedure for calibrations of triaxial magnetometers is presented. The procedure uses a triaxial Helmholtz coil system and an Overhauser scalar magnetometer and is performed in the Earths field range. The triaxial coils are first calibrated with the Overhauser magnetometer, and subsequently, a triaxial magnetometer calibration is performed. As opposed to other calibration approaches, neither Earths field nulling system nor movements of the magnetometer are needed. A real calibration test was carried out-the extended calibration uncertainty was better than 430 ppm in sensitivity and 0.06° in orthogonality.

Biofilm detection by the impedance method

The impedance method was used to detect bacterial layer on the surface of micro-electrodes. The interdigital electrodes arrangement was simulated by FEM to determine the detection distance of the sensor. Then, the KB-12 sensor with spacing 15 µm was selected as the most suitable sensor. For experiments, Escherichia coli was chosen as a typical representative of a biofilm creating bacterium and the bacterial growth was measured during 12 hour intervals. The impedance of the sensor KB-12 was changed by 10 percent when covered with a layer of bacteria.

Long-range magnetic tracking

Two magnetic trackers are described in this paper. The first one is fully magnetic and has 1 meter range. This device can measure distance with 1 mm resolution and 1 cm total accuracy. The second system is a hybrid tracker using active magnetic ranger, three optical gyros and three micromachined inclinometers. It has 15 m range and for distances below 5 m the position accuracy is 50cm. The heading error is below 0.1 deg.

Calibration procedure for triaxial magnetometers without a compensating system or moving parts

A calibration procedure for calibrations of triaxial magnetometers is presented. The procedure uses triaxial Helmholtz coil system and Overhauser scalar magnetometer and is performed in the Earths field range. The triaxial coils are first calibrated with the help of Overhauser magnetometer and subsequently the triaxial magnetometer calibration is performed. As opposed to other approaches, neither Earths field nulling system is needed, nor are movements of the magnetometer. Calibration uncertainty better than 200 ppm in sensitivity and 0.02 degrees in orthogonality can be achieved.

Precise Scalar Calibration of a Tri-Axial Braunbek Coil System

A calibration of the well-defined Braunbek coil system was carried out using the scalar method. The whole measuring setup was designed to minimize the uncertainty of the scalar calibration procedure. The measurement time as well as the sampling ratio were adjusted to reduce the influence of the ambient magnetic field variation. We calibrated the coil sensitivity with the uncertainty of 30 ppm and orthogonality with the uncertainty <;0.01°. The results were compared with a different technique.

Long-Range Magnetic Tracking System

This paper presents a new long-range full 3-D magnetic tracking system for horizontal directional drilling, and describes its performance. The system is able to determine the full 3-D mutual position of the receiver with respect to the transmitter. The system presented here belongs to the category of hybrid trackers using an active magnetic ranger, an optical gyro, and three micromachined inclinometers. The gyro is used for dead-reckoning navigation over long distances (up to 2 km), and the magnetic tracking system, consisting of a coil magnetic transmitter and a magnetometer receiver, is used when two drill heads are approaching each other beneath the surface at the assumed meeting point. The functionality of the system was verified for the maximum range of 17 m with 1,2-m rms accuracy, and with 0,34-m rms accuracy for the range below 10 m.