Measuring and testing – Liquid level or depth gauge – Thermal type
Patent
1989-12-01
1991-04-16
Yasich, Daniel M.
Measuring and testing
Liquid level or depth gauge
Thermal type
73304R, 324721, G01F 2324
Patent
active
050072889
ABSTRACT:
A heat radiating type liquid level sensor comprises a liquid level measuring resistor having a first temperature coefficient and an inverting amplifier gain of which is dependent on the change in resistance of an input resistor thereof. The input resistor has a second temperature coefficient. The liquid level measuring resistor and the input resistor are placed side by side so that the input resistor can experience the same ambient temperature as the liquid level measuring resistor. The first temperature coefficient is set to a greater value than that the second temperature coefficient taking into consideration the temperature dependency of the resistor-to-air thermal resistance Rth of the liquid level measuring assembly, the temperature coefficient of the liquid level measuring resistor Ro, changes in liquid level due to thermal expansion of the liquid, and the maximum liquid level of the liquid tank, so that the liquid level sensor can provide an output indicative of the total weight of the liquid in the liquid tank. The desired value of the second temperature coefficient may be achieved by combining, in series connection or parallel connection, a resistor Ri of the same lot as the liquid level measuring resistor Ro is manufactured and a resistor Rs that has a negligibly small temperature coefficient as compared to that of Ri.
REFERENCES:
patent: 3205709 (1965-09-01), Gearing et al.
patent: 4163391 (1979-08-01), Bezard et al.
patent: 4217544 (1980-08-01), Schmidt
patent: 4525850 (1985-06-01), Miller
patent: 4717811 (1988-01-01), Fujii
Kataoka Ichiro
Sasaki Kazuyuki
Yasich Daniel M.
Yazaki -Corporation
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