An improved proton magnetometer for Earth's magnetic field observation
As a precision instrument to measure the earth magnetic field, proton magnetometer is widely used in different fields such as geological survey, buried objects detection and earth field variations. Due to poor signal to noise ratio (SNR) of the system, proton magnetometer suffers from low sensitivity which directly affects the performance. In order to increase the sensitivity, we present an improved proton magnetometer. First, the effect of matching resistance on Q value is discussed to enhance SNR, and high matching resistance has been chosen to improve the Q value of the resonant circuit. Second, noise induced by pre-amplifier is investigated in order to obtain low noise signal, and we adopt the JFET with noise figure less than 0.5dB as the pre-amplifier. Third, by using band-pass filter, low-noise output signal is obtained. Fourth, the method of period measurement based on CPLD is employed to measure frequency of the square wave shaped from the output sinusoidal signal. High precision temperature compensate crystal oscillator (TCXO) has been used to improve the frequency measurement accuracy. Last, experimental data is obtained through field measurements. By calculating the standard deviation, the sensitivity of the improved proton magnetometer is 0.15nT for Earth’s magnetic field observation. Experimental results show that the new magnetometer is sensitive to earth field measurement.
Advanced Proton Magnetometer Design and its Application for Absolute Measurement
A new processor controlled Proton Magnetometer design and its application for an automated absolute measurement will be presented in this paper. The new design is based on an online signal processing of single period measurements of the sensor signal, aiming to improve the resolution and to valuate the signal quality. Applying a cylindrical coil for auxiliary fields, optimized for high homogeneity, a measurement of the geomagnetic field vector can be realized. To demonstrate the need for homogeneous coils, the relation between the homogeneity of the probe volume and the relaxation of the resulting sensor signal will be shown. In order to perform an absolute measurement, the system is equipped with a telescope, aligned along the coil axis and it can be rotated by a motor about its vertical axis. In contrast to conventional methods, the requirements on manual skills of the observer are quite moderate. Furthermore, an option for full automation is provided.
Development of a high sensitivity potassium magnetometer for near surface geophysical mapping
Dr Ivan Hrvoic, Greg M. Hollyer and Mike Wilson of Canadian company GEM Advanced Magnetometers, and Dr Anthony Szeto (York University, Toronto) discuss how development of its Overhauser magnetometer system led to a new potassium magnetometer/gradiometer for high sensitivity work in near surface geophysical mapping.