Abstract
Abstract A method for calculating quality estimation of the magnetic field value measured by proton-precession magnetometers from data of single measurement is presented. This method is appropriate for frequency measurement algorithms which process time-series of signal’s zero crossing. Expressions for measurement error estimation are obtained taking into account signal decay and correlated noise. Presented formulas allow a result reliability to be estimated immediately in single measurement and give an opportunity for complex control of a device performance. Correlation and relaxation corrections are given. It was experimentally tested that the standard deviation of measurements is in a good qualitative agreement with presented error estimation.
Highlights
One of the most commonly used high-precision methods for geomagnetic field measurement is based on the phenomena of nuclear magnetic resonance (Primdahl, 1998)
The Quality Measurement Criterion (QMC) expressed by Eq (8) is build-in function in these devices
As shown in the previous section, the expressions for the quality measurement criterion QMC presented in this paper provide us a reliability to be estimated immediately in single measurement excepting long-period variations in the geomagnetic field
Summary
One of the most commonly used high-precision methods for geomagnetic field measurement is based on the phenomena of nuclear magnetic resonance (Primdahl, 1998). The geomagnetic equipment accuracy strongly depends on service conditions, such as intrinsic noise, external disturbance, the presence of instability and measured field gradient. Many modern magnetometers have such built-in functions, a numerical system of estimation or time-averaged signal/noise for example (Freedman and Roualt, 1989). Where n is a number of precession half-period between the two neighbouring crossing, ρ(t) = exp(−t/τC ) expresses the normed correlation function for receiving circuit tuned to the signal frequency ω, τC is correlation time of a magnetometer’s receiving circuit noise, and σ 2 is output noise dispersion. The standard deviation of the calculated geomagnetic field value for non-damped signal and uncorrelated Gaussian noise is σ
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