SE336976B - - Google Patents

Abstract

1,126,381. Measuring temperature electrically; resistance measurements. BUZZARDS CORP. Sept. 7, 1965 [Sept. 11, 1964; April 29, 1965], No. 38234/ 65. Headings GiN and G1U. Temperature at a remote location is measured by a thermistor 25 (Fig. 2) whose resistance is compared with that of an adjustable variable resistor 30. Each resistance 25, 30 is shunted by a diode 28, 34 respectively, poled in opposite directions, and connected in series to a constant current D. C. source 36 which is reversed at a regular rate, so that the voltage across the appropriate resistor in the half-cycle when its diode shunt is open-circuit is proportional to the value of the resistance. The voltages are composed in a differential amplifier, and a servomotor adjusts the standard resistor 30 until the difference is zero, simultaneously driving a recorder 44. Alternative methods of inter-connecting the thermistor 25 and adjustable resistor 30 are described Figs. 6a, 6b, (not shown). The system is described in relation to apparatus for determining the relationship between temperature and depth in a body of water, and comprises a probe released from a ship to record temperature against depth and optionally also velocity of sound as it falls through the water. The thermistor 25 is located in the nose of the probe, and connected to the ship by a single core cable 16, using the sea as the signal return path 22 between electrodes 18 on the probe and 20 on the ship. The resistances 23 of the cable and return path are common to the measurements in both half-cycles, and so do not affect accuracy. The rate of reversal of the applied D. C. is continuously reduced as the probe falls to keep the effect of the shunt capacity between the electrodes 18, 20 at a minimum.