GB2341684A - Apparatus for sensing the level of water in a tank - Google Patents

Apparatus for sensing the level of water in a tank Download PDF

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Publication number
GB2341684A
GB2341684A GB9826900A GB9826900A GB2341684A GB 2341684 A GB2341684 A GB 2341684A GB 9826900 A GB9826900 A GB 9826900A GB 9826900 A GB9826900 A GB 9826900A GB 2341684 A GB2341684 A GB 2341684A
Authority
GB
United Kingdom
Prior art keywords
water
electrodes
water tank
level
tank
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB9826900A
Other versions
GB9826900D0 (en
Inventor
Jae-Gyeong Park
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
WiniaDaewoo Co Ltd
Original Assignee
Daewoo Electronics Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Daewoo Electronics Co Ltd filed Critical Daewoo Electronics Co Ltd
Priority to GB9826900A priority Critical patent/GB2341684A/en
Publication of GB9826900D0 publication Critical patent/GB9826900D0/en
Publication of GB2341684A publication Critical patent/GB2341684A/en
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
    • G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm 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
    • G01F23/24—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm 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 by measuring variations of resistance of resistors due to contact with conductor fluid
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
    • G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm 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
    • G01F23/24—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm 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 by measuring variations of resistance of resistors due to contact with conductor fluid
    • G01F23/241—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm 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 by measuring variations of resistance of resistors due to contact with conductor fluid for discrete levels
    • G01F23/243—Schematic arrangements of probes combined with measuring circuits

Landscapes

  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)

Abstract

First and second electrodes 20,30 are mounted spaced apart, and at different levels, in a water tank 10. A bi-directional photocoupler 40 has a light-receiving transistor Q and generates a water level sensing signal based on whether the first and second electrodes are electrically connected by the water in the tank. A microprocessor 50 causes supply voltages to be applied to the electrodes and determines the level of water in the tank based on the water level sensing signal from the bi-directional photocoupler. The microprocessor periodically changes the polarities of the voltages applied to the electrodes to prevent electrolytes in the water from attaching to the electrodes.

Description

2341684 APPARATUS FOR SENSING THE LEVEL OF WATER IN A TANK The present
invention relates to apparatus for sensing the level of water in a water tank.
It 'is known to determine the level of the water in a water tank by utilising the conductivity of the water. However, in known apparatus electrolytes and foreign material in the water become attached to the electrodes which are mounted in the water tank. In time, this process prevents the flow of electric current between the electrodes and thereby interferes with the operation of the water level determining process.
It is an object of the present invention to seek to overcome the problems encountered in the known apparatus.
According to the present invention there is provided apparatus for sensing the level of water in a water tank, said apparatus comprising:
first and second electrodes mounted in said water tank at different levels such that said electrodes are spaced apart; means for applying supply voltage to said electrodes; and means for generating a water level sensing signal representative as to whether or not the first and second electrodes are electrically connected by the water in the tank; _.
wherein said means for applying supply voltage to said electrodes is arranged to periodically change the polarities of the voltages supplied to the electrodes.
The invention also extends to an apparatus for sensing a water level in a water tank comprising:
a first electrode mounted in the water tank; a second electrode mounted apart from the first electrode in the water tank; a bi-directional photocoupler having a light-receiving transistor, and for generating a water level sensing signal based on whether the first and second electrodes are electrically connected; and 2 a microprocessor for alternately changing polarities of supply voltages to the first and second electrodes and for determining the level of water in the water tank based on the water level sensing signal from the bi- directional photocoupler.
In an embodiment, the water level sensing signal is obtained from turn-on and turn-off of the light-receiving transistor of the bi-directional photocoupler.
The bi-directional photocoupler may be connected in series with either the first electrode or the second electrode, and the supply voltages are preferably provided through the bi-directional photocoupler.
Alternate changes of the polarities of supply voltages to the first and second electrodes prevent electrolytes in the water from attaching to the first and second electrodes.
An embodiment of the present invention will hereinafter be described, by way of example, with reference to the accompanying drawings, in which:
Figure 1 is a schematic view of a conventional apparatus for sensing the water level in a water tank; and Figure 2 shows an apparatus of an embodiment of the invention, for sensing the water level in a water tank.
Figure 1 shows schematically a conventional apparatus for sensing the water level in a water tank.
The apparatus shown in Figure 1 includes first and second electrodes 2 and 3 spaced apart in the water tank 1. A voltage of +5V is applied to one of the two electrodes 2 and 3, and the other electrode is electrically connected to a microprocessor 4 through resistors RO and R1.
If the water level is below the levels of the first and second electrodes 2 and 3, the first and second electrodes 2 and 3 are electrically disconnected. Thus, a OV(Ovolt), that is, ground voltage, is applied to the microprocessor 4 through the resistor R1. When the first and second electrodes 2 and 3 are both immersed in the water in the water tank 1, the first and second electrodes 2 and 3 3 are electrically connected. In this case, a voltage of +5V is applied to the microprocessor 4. Accordingly, the microprocessor 4 is able to sense the water level in the water tank 1.
In the apparatus of Figure 1, when the first and second electrodes 2 and 3 are both under water in the water tank and electrically connected to each other, foreign material and/or electrolytes in the water become attached on the first and second electrodes 2 and 3, so that the flow of an electric current between the first and second electrodes 2 and 3 is prevented.
Figure 2 shows an apparatus for sensing the water level in a water tank according to an embodiment of the invention. As shown in Figure 2, the apparatus comprises a first electrode 20 and a second electrode 30, a bi directional photocoupler 40, and a microprocessor 50. The first and second electrodes 20 and 30 are mounted in the water tank 10 according to the water levels to be sensed. The first and second electrodes 20 and 30 are spaced apart to each other, so that the first and second electrodes 20 and 30 are electrically disconnected.
The emitter of a light-receiving transistor Q of the bi-directional photocoupler 40 is grounded, the collector thereof is supplied with a voltage of +5V from an external power source (not shown) through a first resistor R2. The collector of the light-receiving transistor Q is electrically connected with a first terminal PI of the microprocessor 50. The first electrode 20 is connected with one terminal of first and second light-emitting diodes D1 and D2 of the bi directional photocoupler 40. The other terminal of the first and second light emitting diodes D1 and D2 is connected to a second terminal P2 of the microprocessor 50 through a second resistor R3. One terminal of a third resistor R4 and the positive (+) terminal of a capacitor C1 are connected to a node N2 at which the second terminal P2 of the microprocessor 50 and the second resistor R3 are connected. The other terminal of the third resistor R4 is connected to the external power source, and the negative (-) terminal of the capacitor C1 is grounded.
The second electrode 30 is connected to the third terminal P3 of the microprocessor 50 through a fourth resistor R5. One terminal of a fifth resistor 4 R6 is connected to a node N3 at which the fourth resistor R5 and the third terminal P3 of the microprocessor 50 are connected. The other terminal of the fifth resistor R6 is connected to the external power source. The node N3 is connected to a second capacitor C2 whose negative terminal is grounded.
The microprocessor 50 enables the first terminal P2 or the second terminal P3 to be alternately connected or disconnected to the ground, so that the microprocessor 50 controls the electric power supply from the external power source to the first electrode 20 and the second electrode 30. That is, the microprocessor 50 supplies a certain voltage to the first and second electrodes 20 and 30 with a certain frequency.
Further, the microprocessor 50 senses the water level in the water tank 10 based on the collector voltage of the light-receiving transistor Q of the bi- directional photocoupler 40.
In operation, and as stated above, the microprocessor 50 alternately grounds the second and third terminals P2 and P3 whereby the microprocessor 50 enables electric power to be supplied to the first and second electrodes 20 and 30. That is, the second terminal P2 is grounded, the third terminal P3 is disconnected, and the first electrode 20 is electrically grounded, so that the voltage of +5V is supplied to the second electrode 30 through the fourth and fifth resistors R5 and R6. As a certain time period lapses, the microprocessor 50 enables the second terminal P2 to be disconnected and the third terminal P3 to be grounded, so that the voltage of +5V is supplied to the first electrode 20 through the second and third resistors R3 and R4 and the bi- directional photocoupler 40, and the second electrode 30 is grounded. The microprocessor 50 repeats this control cycle with a predetermined frequency.
If the level of the water in the water tank 10 is above the levels of both of the first and second electrodes 20 and 30, the first and second electrodes 20 and 30 are electrically connected by electrolytes in the water. In this case, the first and second diodes D1 and D2 of the bi-directional photocoupler 40 emit light, and the light-receiving transistor Q is turned on. As the light- receiving transistor Q is turned on, the voltage of OV, which is an ideal value of voltage, is supplied to the first terminal P1 of the microprocessor 50 as a water level sensing signal. If the voltage of OV is inputted to the microprocessor 50 as the water level sensing signal from the photocoupler 40, the microprocessor 50 determines that the water level is higher than the standard level.
When the first and second electrodes 20 and 30 are electrically connected, electrolyte in the water collects around the first and second electrodes 20 and 30. However, as the microprocessor 50 changes the polarities of the first and second electrodes 20 and 30 with the certain frequency, the first and second electrodes 20 and 30 are prevented from being damaged.
Furthermore, malfunctioning of the water level sensing apparatus by electrolyte is prevented.
In the case where the water level in the water tank 10 is lower than the levels of the first and second electrodes 20 and 30, the first and second electrodes 20 and 30 are electrically disconnected. In this case, the first and second diodes DI and D2 of the bi-directional photocoupler 40 are disabled, so that the light-receiving transistor 0 is turned off. As the light- receiving transistor Q is turned off, the voltage of 5V is supplied to the first terminal P1 of the microprocessor 50 as the water level sensing signal. If the voltage of 5V is inputted as the water level sensing signal to the microprocessor 50 from the photocoupler 40, the microprocessor 50 determines that the water level, based on the voltage of 5V, is lower than the standard level.
It will be appreciated that modifications in, and variations to, the embodiments as described and illustrated may be made within the scope of the appended claims.
6

Claims (6)

1 Apparatus for sensing the level of water in a water tank, said apparatus comprising:
first and second electrodes mounted in said water tank at different levels such that said electrodes are spaced apart; means for applying supply voltage to said electrodes; and means for generating a water level sensing signal representative as to whether or not the first and second electrodes are electrically connected by the water in the tank; wherein said means for applying supply voltage to said electrodes is arranged to periodically change the polarities of the voltages supplied to the electrodes.
2. Apparatus as claimed in Claim 1, where said water level sensing signal generating means comprises a bi-directional photocoupler.
3. An apparatus for sensing a water level in a water tank, comprising: 20 a first electrode mounted in the water tank; a second electrode mounted apart from the first electrode in the water tank; a bi-directional photocoupler having a light-receiving transistor, and for generating a water level sensing signal based on whether the first and second electrodes are electrically connected; and a microprocessor for alternately changing polarities of supply voltages to the first and second electrodes and for determining the level of water in the water tank based on the water level sensing signal from the bi- directional photocoupler.
4. Apparatus as claimed in Claim 3, wherein the water level sensing signal is obtained from turn-on and turn-off of the light-receiving transistor of the bidirectional photocoupler.
5. Apparatus as claimed in Claim 3 or Claim 4, wherein the bi-directional photocoupler is connected in series with either the first electrode or the second I, , D 7 electrode, and the supply voltages are provided through the bi- directional photocoupler.
6. Apparatus for sensing the level of water in a water tank substantially as hereinbefore described with reference to Figure 2 of the accompanying drawings.
GB9826900A 1998-12-07 1998-12-07 Apparatus for sensing the level of water in a tank Withdrawn GB2341684A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9826900A GB2341684A (en) 1998-12-07 1998-12-07 Apparatus for sensing the level of water in a tank

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9826900A GB2341684A (en) 1998-12-07 1998-12-07 Apparatus for sensing the level of water in a tank

Publications (2)

Publication Number Publication Date
GB9826900D0 GB9826900D0 (en) 1999-01-27
GB2341684A true GB2341684A (en) 2000-03-22

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB9826900A Withdrawn GB2341684A (en) 1998-12-07 1998-12-07 Apparatus for sensing the level of water in a tank

Country Status (1)

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GB (1) GB2341684A (en)

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2005415A (en) * 1977-09-22 1979-04-19 Honeywell Inc Fluid level detection system
US4263587A (en) * 1979-04-09 1981-04-21 International Telephone And Telegraph Corporation Liquid level control system
GB2063484A (en) * 1979-11-19 1981-06-03 Honeywell Inc Resistive fluid level detecting system
US4465088A (en) * 1980-09-03 1984-08-14 Vosper George W Construction of low water level sensing device for hot water boiler
JPH05288592A (en) * 1992-04-09 1993-11-02 Mitsubishi Electric Corp Liquid level detector
GB2288238A (en) * 1994-04-07 1995-10-11 Chromalock Ltd Monitoring device for liquid levels
US5668536A (en) * 1996-04-16 1997-09-16 Caterpillar Inc. Fluid level sensing apparatus
US5775164A (en) * 1995-11-16 1998-07-07 Brother Kogyo Kabushiki Kaisha Remaining liquid quantity detecting device

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2005415A (en) * 1977-09-22 1979-04-19 Honeywell Inc Fluid level detection system
US4263587A (en) * 1979-04-09 1981-04-21 International Telephone And Telegraph Corporation Liquid level control system
GB2063484A (en) * 1979-11-19 1981-06-03 Honeywell Inc Resistive fluid level detecting system
US4465088A (en) * 1980-09-03 1984-08-14 Vosper George W Construction of low water level sensing device for hot water boiler
JPH05288592A (en) * 1992-04-09 1993-11-02 Mitsubishi Electric Corp Liquid level detector
GB2288238A (en) * 1994-04-07 1995-10-11 Chromalock Ltd Monitoring device for liquid levels
US5775164A (en) * 1995-11-16 1998-07-07 Brother Kogyo Kabushiki Kaisha Remaining liquid quantity detecting device
US5668536A (en) * 1996-04-16 1997-09-16 Caterpillar Inc. Fluid level sensing apparatus

Also Published As

Publication number Publication date
GB9826900D0 (en) 1999-01-27

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