A Proton Precession Magnetometer

Abstract

A simple portable proton precession magnetometer designed and constructed for Kodaikanal Observatory is described. Except for the signal amplifier, the instrument is transistorized. The accuracy of measurement of absolute value of the earth`s total field with the magnetometer is plus or minus 1 gamma. The precession signal voltage from the sampling coil is amplified and squared by a Schmitt trigger circuit, the output of which drives 10 stages of binary dividers. The first pulse in the output of the chain of dividers opens a gate allowing pulse from a 100 Kc/s crystal oscillator to pass to a pulse counter. The pulse immediately following the opening pulse closes the gate. By suitable feed back of this closing pulse any following pulse is prevented from opening the gate again. For the next observation, a manual resetting is necessary. The number of 100 Kc/s pulses counted are used to compute the scalar field