A Thermostatted Magnetometer Channel

A channel for measuring the magnetic flux density based on four integrated Hall-effect magnetic sensors (IHMSs) is described. Built-in thermal compensation and dynamic offset cancellation circuits of IHMSs do not eliminate the sensor’s magnetic sensitivity drift due to the thermomechanical packaging stresses that causes an output-voltage offset. The placement of the sensors in a thermostatically controlled cell, as well as the design and circuit solutions related to the spatial orientation of the sensors relative to the magnetic induction vector and to the IHMS output voltage processing algorithm, made it possible to minimize the instability and increase the signal-to-noise ratio of the channel’s ADC input voltage. The design and operation of the hardware–software-based PI controller that regulates the thermostatted cell temperature are considered. The developed channel is used to measure the magnetic-field flux density of the magnetic analyzer of the mass-spectrometric system for isotopic analysis of noble gases and provides the following specifications: the measurement range is ±512 mT; the bandwidth is 0–4 Hz; the noise-free code resolution of the channel is 16.3 bits; the peak-to-peak value of the equivalent input magnetic noise in the bandwidth is 0.012 mT; and the equivalent input long-term drift of measurements is no more than 0.08 mT within 48 h.