Abstract: A method for thermal diffusivity measurement includes the steps of periodically heating a sample with a heat source modulated at an operating frequency, detecting an ac temperature of the sample at a detection point a predetermined distance apart from a heating point of the sample, the ac temperature being a periodic temperature oscillation, measuring a phase of the detected ac temperature by a phase sensitive detection operation, maintaining the phase constant by controlling the operating frequency of the heat source based on the measured phase to realize a constant-wave-number condition in which both a wave number and a thermal diffusion length are kept constant, and determining the thermal diffusivity of the sample based on the relative change in the operating frequency under the constant-wave-number condition.

Abstract: A temperature sensor includes a first sensor section having first and second conductors connected at their one ends and defining macroscopic current paths directed in different directions with respect to that of a magnetic field and having resistance values such that the magnetic field produces identical changes in resistance therein, a similarly constituted second sensor section having third and fourth conductors connected to the second and first conductors, and heat coupling means for keeping the temperature of the first and second sensor sections uniform.

Abstract: A pressure sensor for fluids includes first, second, third and fourth strain gauges disposed on a diaphragm with prescribed spacing so that the majority of current flowing through the first strain gauge has a predetermined direction and the majority of current flowing through each of the second, third and fourth strain gauges has a direction identical with or opposite to the predetermined direction, first and second conductors interconnecting the first and second strain gauges and the third and fourth strain gauges, and first and second voltage leads connected to the first and second conductors from the side identical with or opposite to the direction of a vector product determined by a vector in the direction of current flow through the conductors and a vector in a direction normal to the diaphragm. The configuration causes voltages produced in the conductors by the Hall effect to cancel out, thus making the pressure sensor immune to the effect of magnetic fields.

Abstract: A thermometer comprises a first sample space having a liquefiable gas sealed therein and a second sample space partitioned from the first sample space by a pressure difference detecting element and having a liquefiable gas sealed therein in conjunction with an adsorbent. As this thermometer is cooled to cryogenic temperatures, the second sample space is vacuumized by the action of the adsorbent. As the pressure difference detected by pressure difference detecting element at this is equal to the vapor pressure in the first sample space, the temperature can be accurately measured from the detected pressure difference.

Abstract: A thermometer capable of providing temperature measurement over a wide temperature range comprises at least one temperature detection unit consisting of a first superconductor as a core, and a normal conductor and a second supercondutor sequentially superposed coaxially on the first superconductor; a first power source disposed to pass electric current between the first and second superconductors, a second power source disposed between the opposite terminals of the first superconductor, and a voltmeter connected to the first and second superconductors. This thermometer effects measurement of temperature by fixing the value of the electric current from the first power source and changing the value of the electric current from the second power source thereby causing cyclic change of the voltage and measuring the increment of electric current from the second power which is required to cause one cycle of change of the voltage.