FLUXGATE MAGNETOMETER FOR TEMPERATURES UP TO 180°C
Patrick Sebbes – Frank Ludwig – Meinhard Schilling
For applications in geothermal drilling fluxgate magnetometers in Vacquier geometry are investigated. The high operation temperatures in these applications require new selection of materials, especially for the core where Vitroperm 800R from Vaccumschmelze is employed here. The apparent permeability of the Vitroperm core at 260°C was found to be 6% lower than at room temperature. We characterize the fluxgate sensor by its closed loop sensitivity in dependence of temperature up to 180°C. At room temperature, the sensor exhibits a closed-loop sensitivity of 130.000 V/T, a linearity of better than 40 ppm in the range ±50 μT and a noise at 100 Hz of 15 pT/√Hz. The sensitivity of the sensor operated in a current-compensation loop at 180°C is only 0.6% higher than the room temperature value, mainly caused by the temperature coefficient of the resistance of the copper wire of the secondary coil.
Keywords: Fluxgate sensor, Vacquier geometry, high temperature operation