Liquid level sensing apparatus and method
First Claim
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, andthe 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.
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Accused Products
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.
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Citations
3 Claims
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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:
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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. - View Dependent Claims (2)
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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:
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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.
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Specification