Data acquisition system for noise measurement on magnetic sensors

In this paper, we describe a principle of noise induction by varying the amplitude of a magnetic field in which we operate four magnetoresistors (sensors). In accordance with this principle, we achieve an acquisition system used to collect all necessary information for noise measurement on magnetic sensors. The magnetic field used in measurements can be modified by varying both its orientation and amplitude. The sensitivity coefficient, ΔR/ΔH, of magnetoresistors is established accurately by a technique which uses a lock-in amplifier and a function generator. The noise is collected with ultra-low-noise amplifiers and then is applied at the measurement system based on a personal computer (PC) and a data acquisition system. In addition, we use a PC to automate the measuring system. The circuit presented here has the capability to control the bias circuitry (bias current through sensors). The additional noise introduced by the instrumentation and circuitry is negligible