Liquid level sensing apparatus and method

Patent metadata

Field	Value
Publication number	US-9423286-B2
Application number	US-201314374272-A
Country	US
Kind code	B2
Filing date	Jan 25, 2013
Priority date	Jan 26, 2012
Publication date	Aug 23, 2016
Grant date	Aug 23, 2016

Abstract

Provided is a apparatus for sensing a liquid level reliably based solely on an analog process even if a liquid held in a container boils, causing the liquid level to fall. A liquid level sensing apparatus includes: a probe selection unit configured to select a probe whose heater is to be activated from among the plurality of probes; an input unit configured to receive an output of the temperature sensor of the probe selected by the probe selection unit, the output being received as a temperature signal directly in the form of an analog quantity; a signal processing unit configured to output a processing signal of the temperature signal in synchronization with activation of the heater; a calculation unit configured to arithmetically process the temperature signal and the processing signal and output a result; a gas/liquid discrimination unit configured to discriminate whether the detecting point exists in a gas phase or a liquid phase based on the output result of the arithmetic processing; and a display unit configured to indicate a discrimination result produced by the gas/liquid discrimination unit.

First claim

The invention claimed is:

1. A liquid level sensing apparatus which measures a liquid level in a liquid holding vessel based on temperature signals from a plurality of probes placed at fixed intervals in a vertical direction of the liquid holding vessel, wherein each of the probes includes a temperature sensor and a heater enclosed in the probe and the heater is placed in a neighborhood of a detecting point of the temperature sensor, the liquid level sensing apparatus comprising:
a probe selection unit configured to select a probe whose heater is to be activated from among the plurality of probes;
an input unit configured to receive an output of the temperature sensor of the probe selected by the probe selection unit, the output being received as a temperature signal directly in a form of an analog quantity;
a signal processing unit configured to output a processing signal of the temperature signal in synchronization with activation of the heater;
a calculation unit configured to arithmetically process the temperature signal and the processing signal and output a result;
a gas/liquid discrimination unit configured to discriminate whether the detecting point exists in a gas phase or a liquid phase based on the output result of the arithmetic processing; and
a display unit configured to indicate a discrimination result produced by the gas/liquid discrimination unit,
wherein the calculation unit finds one of a difference and a quotient between the temperature signal and the processing signal and outputs a result, and
the signal processing unit is one of a hold circuit and a first order delay circuit, wherein the hold circuit holds the processing signal at a level of the temperature signal at a start time of the heat supply and the first order delay circuit outputs a first order delay response to the temperature signal.

2. The liquid level sensing apparatus according to claim 1 , further comprising a liquid level determination unit configured to determine the liquid level based on the discrimination result produced by the gas/liquid discrimination unit.

3. A liquid level sensing method for measuring a liquid level in a liquid holding vessel based on temperature signals from a plurality of probes placed at fixed intervals in a vertical direction of the liquid holding vessel, wherein each of the probes includes a temperature sensor and a heater enclosed in the probe and the heater is placed in a neighborhood of a detecting point of the temperature sensor, the liquid level sensing method comprising:
selecting a probe whose heater is to be activated from among the plurality of probes;
receiving an output of the temperature sensor of the selected probe as a temperature signal directly in a form of an analog quantity;
outputting a processing signal of the temperature signal in synchronization with activation of the heater;
arithmetically processing the temperature signal and the processing signal and outputting a result;
discriminating whether the detecting point exists in a gas phase or a liquid phase based on the output result of the arithmetic processing; and
displaying a discrimination result based on at least one of the selected probes,
wherein the arithmetically processing finds one of a difference and a quotient between the temperature signal and the processing signal and outputs a result, and
the outputting a processing signal utilizes one of a hold circuit and a first order delay circuit, wherein the hold circuit holds the processing signal at a level of the temperature signal at a start time of the heat supply and the first order delay circuit outputs a first order delay response to the temperature signal.

Assignees

• Toshiba Kk

Inventors

• Nishimura Kentaro
• Nagase Katsumoto
• Shiraishi Fujio
• Takada Yuka

Classifications

• G01F23/241 Primary

  for discrete levels · CPC title

• G01F23/243

  Schematic arrangements of probes combined with measuring circuits · CPC title

• G21C19/07

  Storage racks; Storage pools · CPC title

• G21C17/035

  Moderator- or coolant-level detecting devices {(indicating or measuring liquid level in general G01F23/00)} · CPC title

• G01F23/22 Primary

  by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water (involving the use of floats G01F23/30) · CPC title