Magnetic Fluid Based High Precision Temperature Sensor

We have developed a high precision (3.7 mK) temperature sensor using nanomagnetic fluid bearing. The device is based on the basic principle of Charles law (v $\propto $ T). For this, we have prepared kerosene-based magnetic fluid for ferrofluid bearing formation with permanent magnet. The ferrofluid bearing has very low coefficient of friction ( $\mu _{f} = 0.002$ ), and provides a frictionless movement and perfect sealing. The device is highly sensitive as it uses air as a working media whose coefficient of volume expansion (0.0036) is much larger (20 times) than mercury (0.00018), ethanol (0.00026), and so on usually used in expansion-based thermometers. At constant atmospheric pressure (1 atm), a temperature variation of 1 °C causes a variation of 20 mm (capillary diameter 5 mm) in the position of fluid column. The device has been calibrated and tested using standard calibrated equipment’s. The device shows the high sensitivity of 3.7 (± 0.2) mK and can be used where high accuracy in temperature measurements is required. The device sensitivity and range is easily customizable. The device is capable of finding many useful applications, viz., standards and the calibration of thermometers.