CA2412405A1 - Liquid level gauge and specific gravity calibration therefor - Google Patents
Liquid level gauge and specific gravity calibration therefor Download PDFInfo
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- CA2412405A1 CA2412405A1 CA 2412405 CA2412405A CA2412405A1 CA 2412405 A1 CA2412405 A1 CA 2412405A1 CA 2412405 CA2412405 CA 2412405 CA 2412405 A CA2412405 A CA 2412405A CA 2412405 A1 CA2412405 A1 CA 2412405A1
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Abstract
A battery-powered liquid level gauge includes a tapped voltage divider extending into a liquid-containing vessel and including vertically staggered reed switches at the tap points magnetically coupled to a float member which rises and falls with the level of the liquid and is coupled to an LCD display. The batteries, the display and calibration circuitry are all disposed in a housing mounted on the outside of the vessel. The calibration circuitry includes a first zero set potentiometer in series with a second specific gravity adjustment potentiometer. The zero level is set with the first potentiometer based on a maximum specific gravity and then adjusted for lower specific gravities using the second potentiometer so that the original zero setting need not be changed.
Description
LIQUID LEVEL GAUGE AND
SPECIFIC GRAVITY CALIBRATION THEREFOR
Background This application relates to liquid level gauges of the type used in measuring the fullness of vessels or the depth of liquids contained in vessels, such as tanks or the like, and relates in particular to electronic float-type gauges.
Such gauges utilize a float which rises and falls with the liquid level. Float movement may be guided by a fixed guide tube, which may extend into the vessel from the top thereof. The float carries a permanent magnet for magnetic coupling to a device in the guide tube. In one type of float gauge, the magnetic device may be in the nature of a voltage divider including a tapped impedance with a magnetically operated switch, such as a reed switch, at each tap point. As the liquid level changes, the switches are sequentially closed by the float magnet, which is moving with the liquid level, for applying to a gauge meter or the like a voltage corresponding to the liquid level. Thus, when the vessel is full, the float will be adjacent to the top of the voltage divider for applying a minimum voltage to the meter and, as the liquid level drops, the float will fall with the liquid level, causing sequentially larger voltages to be applied to the meter, indicating greater depths of the float in the vessel corresponding, respectively, to lower liquid levels.
Such liquid level gauges must be calibrated so that the voltage level generated by the float when the tank is full will produce a zero output. This is referred to as a zero set calibration.
The gauge may also be calibrated so that, when the liquid is at a minimum level, the float position will cause a maximum output voltage corresponding to the full range of the gauge, and this may be referred to as a range calibration. However, these zero and range calibrations do not take account of variations in the specific gravity of the liquid, which will cause variation of the depth to which the float sinks in the liquid.
Summary This application is directed to a liquid level gauge which avoids the disadvantages of prior gauges while affording additional structural and operating advantages.
An important aspect is the provision of a liquid level gauge with an improved calibration apparatus.
In connection with the foregoing aspect, another aspect is the provision of a liquid level gauge of the type set forth, which provides a calibration adjustment for variations in specific gravity of the liquid.
In connection with the foregoing aspect, a still further aspect is the provision of a liquid level gauge of the type set forth, which does not affect a zero-level calibration setting.
A still further aspect is the provision of a liquid level gauging calibration method which accounts for variation in specific gravity of the liquid.
Certain ones of these and other features may be attained by providing a liquid level gauge for sensing the level of the surface of a body of liquid in a vessel, the gauge comprising: a float member adapted to float on the surface of the liquid in a position which varies with the level of the surface, a sensing circuit coupled to the float member for sensing the position of the float member, an indicating circuit coupled to the sensing circuit for indicating the liquid level corresponding to the float position, and a calibration circuit for varying the calibration of the sensing circuit in accordance with changes in the specific gravity of the liquid so that the float member will accurately indicate the level of the liquid surface irrespective of the specific gravity of the liquid.
SPECIFIC GRAVITY CALIBRATION THEREFOR
Background This application relates to liquid level gauges of the type used in measuring the fullness of vessels or the depth of liquids contained in vessels, such as tanks or the like, and relates in particular to electronic float-type gauges.
Such gauges utilize a float which rises and falls with the liquid level. Float movement may be guided by a fixed guide tube, which may extend into the vessel from the top thereof. The float carries a permanent magnet for magnetic coupling to a device in the guide tube. In one type of float gauge, the magnetic device may be in the nature of a voltage divider including a tapped impedance with a magnetically operated switch, such as a reed switch, at each tap point. As the liquid level changes, the switches are sequentially closed by the float magnet, which is moving with the liquid level, for applying to a gauge meter or the like a voltage corresponding to the liquid level. Thus, when the vessel is full, the float will be adjacent to the top of the voltage divider for applying a minimum voltage to the meter and, as the liquid level drops, the float will fall with the liquid level, causing sequentially larger voltages to be applied to the meter, indicating greater depths of the float in the vessel corresponding, respectively, to lower liquid levels.
Such liquid level gauges must be calibrated so that the voltage level generated by the float when the tank is full will produce a zero output. This is referred to as a zero set calibration.
The gauge may also be calibrated so that, when the liquid is at a minimum level, the float position will cause a maximum output voltage corresponding to the full range of the gauge, and this may be referred to as a range calibration. However, these zero and range calibrations do not take account of variations in the specific gravity of the liquid, which will cause variation of the depth to which the float sinks in the liquid.
Summary This application is directed to a liquid level gauge which avoids the disadvantages of prior gauges while affording additional structural and operating advantages.
An important aspect is the provision of a liquid level gauge with an improved calibration apparatus.
In connection with the foregoing aspect, another aspect is the provision of a liquid level gauge of the type set forth, which provides a calibration adjustment for variations in specific gravity of the liquid.
In connection with the foregoing aspect, a still further aspect is the provision of a liquid level gauge of the type set forth, which does not affect a zero-level calibration setting.
A still further aspect is the provision of a liquid level gauging calibration method which accounts for variation in specific gravity of the liquid.
Certain ones of these and other features may be attained by providing a liquid level gauge for sensing the level of the surface of a body of liquid in a vessel, the gauge comprising: a float member adapted to float on the surface of the liquid in a position which varies with the level of the surface, a sensing circuit coupled to the float member for sensing the position of the float member, an indicating circuit coupled to the sensing circuit for indicating the liquid level corresponding to the float position, and a calibration circuit for varying the calibration of the sensing circuit in accordance with changes in the specific gravity of the liquid so that the float member will accurately indicate the level of the liquid surface irrespective of the specific gravity of the liquid.
Brief Description of the Drawings For the purpose of facilitating an understanding of the subject matter sought to be protected, there are illustrated in the accompanying drawings embodiments thereof, from an inspection of which, when considered in connection with the following description, the subject matter sought to be protected, its construction and operation, and many of its advantages should be readily understood and appreciated.
FIG. 1 is a fragmentary side elevational view in partial section of a liquid level gauge mounted on a liquid-containing vessel;
FIG. 2 is a reduced, fragmentary, diagrammatic illustration of the vessel and liquid level gauge of FIG. 1;
FIG. 3 is a perspective view of a receiver portion of the liquid level gauge of FIG. l, with the cover removed and top hatch closed;
FIG. 4 is a top plan view of the receiver of FIG. ~, with the top hatch open;
FIG. 5 is an enlarged fragmentary, diagrammatic illustration of a transmitter portion of the liquid level gauge of FIGS. 1 and 2;
FIG. 6 is a functional block diagrammatic illustration of the liquid level gauge of FIGS. 1 and 2; and FIG. 7 is a schematic circuit diagram of the calibration portion of the liquid level gauge of FIG. 6.
Detailed Description Referring to FIGS. 1 and 2, there is illustrated a vessel 10, which may be in the nature of a tank ar the like, having a top wall 11 in which is formed a port 12. The vessel 10 contains a liquid I3 having a surface 14, the level of which is to be sensed.
Referring also to FIGS. 3-5, there is mounted on the top wall 11 a liquid level gauge 20, which includes a generally cylindrical housing 21 having an upper end closed by a circular cap 22, which includes a hinged hatch 23 with a handle knob 24. Formed in the side wall of the housing 21 is a generally rectangular aperture 25 adapted to be closed by a part-cylindrical cover plate 26. The plate 26 has depending legs with apertures 27 adapted to respectively receive tabs 27a mounted on the housing side wall 21 below the aperture 26. Provided at the upper edge of the cover plate 26 are hooks 28, respectively engageable with latches 29 mounted on the cap 22 for securing the cover plate 26 in place.
The housing 21 is mounted on the vessel top wall 11 by means of a pedestal 30, which includes an annular attachment plate 31 fixedly secured to and closing the lower end of the housing 21. Integral with the attachment plate 31 acid depending therefrom is a hollow cylindrical stem 32, integral at its lower end with an annular mounting plate 33 adapted to be fxedly secured to the top wall 1 l, as by threaded fasteners 34, so that the stern 32 is in coaxial communication with the port 12. Fixed to the inner surface of the vessel top wall 11 and depending therefrom coaxial with the port 12 is a hollow guide tube 35.
Disposed coaxially within the guide tube 35 and extending between the base plate 36 and the vessel top wall 11 is a voltage divider tube 37 which communicates with the port 12, the tube 3?
having a guide disk 36 attached to its lower end and being provided with encircling helical compression springs 3 $ and 39, respectively adjacent to its lower and upper ends. The interior of the guide tube 35 communicates with the interior of the vessel 10 through ports 36a and through the bottom of the tube 35 around the guide disk 36. Disposed within the tube 37 is a voltage divider impedance which, for simplicity, is diagrammatically illustrated in FIG. 2 as an elongal:ed continuous resistor, although it will be appreciated that it could have other forms, such as a series of discrete impedances, non-resistive impedance, and the like. One or more batteries 41 may be connected across the voltage divider 40. A float 42 encircles the voltage divider tube 37 and is freely slidable thereaiong, the springs 38 and 39 serving as cushioning stops to limit travel of the float.
The lowermost and uppermost positions of the float are, respectively, illustrated in solid line and broken line in FIG. 1. The float 42 carries one or more cylindrical permanent magnets 43 (see FIG. 5) The voltage divider 40 is provided with a plurality of equidistantly vertically spaced tap points (not shown), connected in parallel to one terminal of a meter 44, respectively through reed switches 45 (FIG. 5), the other terminal of the meter 44 being connected to the battery 41. Thus, it will be appreciated that the voltage divider 40 and the float magnet 43 function as a transmitter within the vessel 10, connected by three wires, which pass up through the port 12, to the battery 41 and meter 44, which are disposed in the housing 21 externally of the vessel 10, the meter 44 serving as a receiver for the transmitted signals, all in a known manner. It will be appreciated that the voltage divider tube 37 is appropriately sealed from exposure to the liquid 13.
In the illustrated embodiment, the reed switches 45 are arranged in a vertically staggered series tapped in a "2-3-2 at-a-time'' sequence. When two adjacent switches, such as the switches A and B in FIG. 5, are closed, the effective electrical tap point is midway therebetween. As the float 42 rises and closes the next switch C, while holding the first two switches A and B closed, the effective tap point is at the midpoint of the switch B, a distance D from the first tap point. As the float continues to rise, the switch A opens, so that only the switches B
and C are closed, so that the effective tap point is midway therebetween, again a distance D from the second tap point. Thus, it can be seen that the switches are vertically spaced so that the sequential tap points are equidistantly spaced a distance D from each other. Accordingly, any inaccuracy would be limited to the distance D plus any meter and circuit tolerances.
Referring to FIGS. 6 and 7, the circuitry of the liquid level gauge 20 is illustrated. The gauge 20 includes an A/D converter and control circuit 50, which may be an integrated circuit of the type sold by Maxim under the designation MAX138. Coupled to the A/D and control circuit 50 is a level sensing circuit 51, which includes the voltage divider 40 and the associated reed switches 45 and float magnet 43. Also connected to the A/D and control circuit 50 is a display circuit 52, which may include an integrated circuit LCD display which is preferably positioned below the housing cap 22 for viewing through the hatch 23 when it is opened, as illustrated in FIG. 4. A DC power supply circuit 53, which includes batteries 41, provides a predetermined DC V+ supply voltage to the circuits 50-52. It will be appreciated that the A/D and control circuit 50 and the display circuit 52 cooperate to perform the function of the meter 44.
Also connected to the A/D and control circuit 50 is calibration circuitry including a range adjustment circuit 54, a zero set circuit 55 and a specific gravity adjustment circuit 56, Referring to FIG. 7, the range adjustment circuit 54 includes a potentiometer 57 having one end thereof connected to the V+ supply voltage and the other end connected to the Reference LO and Common terminals of the circuit 50, the potentiometer 57 having a wiper connected to the Reference HI terminal of the circuit 50. A capacitor 58 is connected across the Reference LO
and Reference HI pins. The wiper may be operable by a suitable control knob (not shown) in the housing 21 when the cover plate 26 is removed for performing the range adjustment calibration.
The zero set circuit 5~ includes a potentiometer 60, having one terminal thereof connected to ground and the other connected to the wiper of a potentiometer 62, one end of which is floating and the other end of which is connected to the V+ supply.
The wiper of the potentiometer 60 is connected to an In LO terminal of the circuit 50. The input from the level sensing circuit 51, i.e., from the tap switches 45, is supplied via a lead 63 through series resistors 64 and 65 to the In HI terminal of the circuit 50. Capacitors 66 and 6 l are connected in parallel across the In LO and In HI terminals. The wiper of the potentiometer 60 is provided with a manually operable knob 60 accessible through the open aperture 25 in the housing 21, while the wiper of the potentiometer 62 is coupled to an actuating knob 62, which may be coaxial with the knob 60. The batteries 41 may be mounted on suitable clips on the inside of the cover plate 26 for connection to the remainder of the circuitry when the cover plate 26 is mounted in place on the housing 21.
The display circuit 52 and the A/C and control circuit 50 may be arranged so that the display circuit 52 will directly display in inches, the depth of the float 5:?
and, therefore, the distance of the liquid levell4, below the maximum level point. In this regard, the "zero" point is set so that the gauge will display 0.00 inches when the float is at its highest position, this zero set being accomplished by adjusting the potentiometer 60. The full range point is set so that the gauge will display the maximum depth when the float is at the bottom of the guide tube, e.g., 60.0 inches.
During this initial calibration of the zero and fully range points, the calibration is made assuming the liquid in the vessel has a maximum specific gravity, e.g., 1.3. A
line may be scribed on the float 42 so that it can be lined up to the zero point on the vessel 10 when calibrating the zero point, and at the 60-inch point when calibrating the full range point. Thus, when the liquid 13 has a specific gravity of 1.3, the gauge 20 will be correctly calibrated and will provide accurate readings of the liquid level.
However, if the liquid 13 in the vessel has a specific gravity less than 1.3, the float 42 will sink lower in the liquid. For example, referring to FIG. l, at a specific gravity of 1.3, the float will sink to a level corresponding to the level 14, whereas at a lower specific gravity it will sink further so that the liquid level will be disposed higher on the float, as at 14a.
Even though the liquid level is at its maximum level, if the specific gravity is below 1.3, the gauge will display a positive depth. To correct the effect of the different float buoyancy in different specific-gravity liquids, the display must be adjusted by the amount of the float "sinkage." To achieve this, an external zero offset reference input or a specific gravity adjustment is provided by the potentiometer 62. By rotating the knob of the potentiometer 62, the zero level can be adjusted, without changing the setting of the zero set potentiometer 60.
Consequently, the range is also "moved" by this same offset amount. By providing a separate potentiometer 62 for specific gravity adjustment, the float line corrections can be effected without altering the initial zero set calibration, which is used as an installation calibration.
A table may be affixed to the housing 21 showing the amount of offset (in inches) for different specific gravities, e.g., from 0.5 to 1.3. The specific gravity adjustment potentiometer 62 is turned until the value displayed on the display circuit 52 is corrected by the amount shown in the table. For example, if the liquid 13 has a specific gravity of 1.0, the corresponding offset given in a table may, e.g., be 0.2 inches. Thus, the specific gravity adjustment potentiometer 62 is turned until the display is reduced by 0.2 inches. For example, if the display 52 were displaying a level of 30.2 inches, the potentiometer 62 is adjusted until the display shows the value of 30.0 inches. The gauge is then considered adjusted for a specific gravity of 1Ø
From the foregoing, it can be seen that there has been provided an improved liquid level gauge with a calibration system which accommodates adjustment fox different specific gravities of liquids being gauged.
The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. While particular embodiments have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the broader aspects of applicant's contribution. The actual scope of the protection sought is intended to be defined in the following claims when viewed in their proper perspective based on the prior art.
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FIG. 1 is a fragmentary side elevational view in partial section of a liquid level gauge mounted on a liquid-containing vessel;
FIG. 2 is a reduced, fragmentary, diagrammatic illustration of the vessel and liquid level gauge of FIG. 1;
FIG. 3 is a perspective view of a receiver portion of the liquid level gauge of FIG. l, with the cover removed and top hatch closed;
FIG. 4 is a top plan view of the receiver of FIG. ~, with the top hatch open;
FIG. 5 is an enlarged fragmentary, diagrammatic illustration of a transmitter portion of the liquid level gauge of FIGS. 1 and 2;
FIG. 6 is a functional block diagrammatic illustration of the liquid level gauge of FIGS. 1 and 2; and FIG. 7 is a schematic circuit diagram of the calibration portion of the liquid level gauge of FIG. 6.
Detailed Description Referring to FIGS. 1 and 2, there is illustrated a vessel 10, which may be in the nature of a tank ar the like, having a top wall 11 in which is formed a port 12. The vessel 10 contains a liquid I3 having a surface 14, the level of which is to be sensed.
Referring also to FIGS. 3-5, there is mounted on the top wall 11 a liquid level gauge 20, which includes a generally cylindrical housing 21 having an upper end closed by a circular cap 22, which includes a hinged hatch 23 with a handle knob 24. Formed in the side wall of the housing 21 is a generally rectangular aperture 25 adapted to be closed by a part-cylindrical cover plate 26. The plate 26 has depending legs with apertures 27 adapted to respectively receive tabs 27a mounted on the housing side wall 21 below the aperture 26. Provided at the upper edge of the cover plate 26 are hooks 28, respectively engageable with latches 29 mounted on the cap 22 for securing the cover plate 26 in place.
The housing 21 is mounted on the vessel top wall 11 by means of a pedestal 30, which includes an annular attachment plate 31 fixedly secured to and closing the lower end of the housing 21. Integral with the attachment plate 31 acid depending therefrom is a hollow cylindrical stem 32, integral at its lower end with an annular mounting plate 33 adapted to be fxedly secured to the top wall 1 l, as by threaded fasteners 34, so that the stern 32 is in coaxial communication with the port 12. Fixed to the inner surface of the vessel top wall 11 and depending therefrom coaxial with the port 12 is a hollow guide tube 35.
Disposed coaxially within the guide tube 35 and extending between the base plate 36 and the vessel top wall 11 is a voltage divider tube 37 which communicates with the port 12, the tube 3?
having a guide disk 36 attached to its lower end and being provided with encircling helical compression springs 3 $ and 39, respectively adjacent to its lower and upper ends. The interior of the guide tube 35 communicates with the interior of the vessel 10 through ports 36a and through the bottom of the tube 35 around the guide disk 36. Disposed within the tube 37 is a voltage divider impedance which, for simplicity, is diagrammatically illustrated in FIG. 2 as an elongal:ed continuous resistor, although it will be appreciated that it could have other forms, such as a series of discrete impedances, non-resistive impedance, and the like. One or more batteries 41 may be connected across the voltage divider 40. A float 42 encircles the voltage divider tube 37 and is freely slidable thereaiong, the springs 38 and 39 serving as cushioning stops to limit travel of the float.
The lowermost and uppermost positions of the float are, respectively, illustrated in solid line and broken line in FIG. 1. The float 42 carries one or more cylindrical permanent magnets 43 (see FIG. 5) The voltage divider 40 is provided with a plurality of equidistantly vertically spaced tap points (not shown), connected in parallel to one terminal of a meter 44, respectively through reed switches 45 (FIG. 5), the other terminal of the meter 44 being connected to the battery 41. Thus, it will be appreciated that the voltage divider 40 and the float magnet 43 function as a transmitter within the vessel 10, connected by three wires, which pass up through the port 12, to the battery 41 and meter 44, which are disposed in the housing 21 externally of the vessel 10, the meter 44 serving as a receiver for the transmitted signals, all in a known manner. It will be appreciated that the voltage divider tube 37 is appropriately sealed from exposure to the liquid 13.
In the illustrated embodiment, the reed switches 45 are arranged in a vertically staggered series tapped in a "2-3-2 at-a-time'' sequence. When two adjacent switches, such as the switches A and B in FIG. 5, are closed, the effective electrical tap point is midway therebetween. As the float 42 rises and closes the next switch C, while holding the first two switches A and B closed, the effective tap point is at the midpoint of the switch B, a distance D from the first tap point. As the float continues to rise, the switch A opens, so that only the switches B
and C are closed, so that the effective tap point is midway therebetween, again a distance D from the second tap point. Thus, it can be seen that the switches are vertically spaced so that the sequential tap points are equidistantly spaced a distance D from each other. Accordingly, any inaccuracy would be limited to the distance D plus any meter and circuit tolerances.
Referring to FIGS. 6 and 7, the circuitry of the liquid level gauge 20 is illustrated. The gauge 20 includes an A/D converter and control circuit 50, which may be an integrated circuit of the type sold by Maxim under the designation MAX138. Coupled to the A/D and control circuit 50 is a level sensing circuit 51, which includes the voltage divider 40 and the associated reed switches 45 and float magnet 43. Also connected to the A/D and control circuit 50 is a display circuit 52, which may include an integrated circuit LCD display which is preferably positioned below the housing cap 22 for viewing through the hatch 23 when it is opened, as illustrated in FIG. 4. A DC power supply circuit 53, which includes batteries 41, provides a predetermined DC V+ supply voltage to the circuits 50-52. It will be appreciated that the A/D and control circuit 50 and the display circuit 52 cooperate to perform the function of the meter 44.
Also connected to the A/D and control circuit 50 is calibration circuitry including a range adjustment circuit 54, a zero set circuit 55 and a specific gravity adjustment circuit 56, Referring to FIG. 7, the range adjustment circuit 54 includes a potentiometer 57 having one end thereof connected to the V+ supply voltage and the other end connected to the Reference LO and Common terminals of the circuit 50, the potentiometer 57 having a wiper connected to the Reference HI terminal of the circuit 50. A capacitor 58 is connected across the Reference LO
and Reference HI pins. The wiper may be operable by a suitable control knob (not shown) in the housing 21 when the cover plate 26 is removed for performing the range adjustment calibration.
The zero set circuit 5~ includes a potentiometer 60, having one terminal thereof connected to ground and the other connected to the wiper of a potentiometer 62, one end of which is floating and the other end of which is connected to the V+ supply.
The wiper of the potentiometer 60 is connected to an In LO terminal of the circuit 50. The input from the level sensing circuit 51, i.e., from the tap switches 45, is supplied via a lead 63 through series resistors 64 and 65 to the In HI terminal of the circuit 50. Capacitors 66 and 6 l are connected in parallel across the In LO and In HI terminals. The wiper of the potentiometer 60 is provided with a manually operable knob 60 accessible through the open aperture 25 in the housing 21, while the wiper of the potentiometer 62 is coupled to an actuating knob 62, which may be coaxial with the knob 60. The batteries 41 may be mounted on suitable clips on the inside of the cover plate 26 for connection to the remainder of the circuitry when the cover plate 26 is mounted in place on the housing 21.
The display circuit 52 and the A/C and control circuit 50 may be arranged so that the display circuit 52 will directly display in inches, the depth of the float 5:?
and, therefore, the distance of the liquid levell4, below the maximum level point. In this regard, the "zero" point is set so that the gauge will display 0.00 inches when the float is at its highest position, this zero set being accomplished by adjusting the potentiometer 60. The full range point is set so that the gauge will display the maximum depth when the float is at the bottom of the guide tube, e.g., 60.0 inches.
During this initial calibration of the zero and fully range points, the calibration is made assuming the liquid in the vessel has a maximum specific gravity, e.g., 1.3. A
line may be scribed on the float 42 so that it can be lined up to the zero point on the vessel 10 when calibrating the zero point, and at the 60-inch point when calibrating the full range point. Thus, when the liquid 13 has a specific gravity of 1.3, the gauge 20 will be correctly calibrated and will provide accurate readings of the liquid level.
However, if the liquid 13 in the vessel has a specific gravity less than 1.3, the float 42 will sink lower in the liquid. For example, referring to FIG. l, at a specific gravity of 1.3, the float will sink to a level corresponding to the level 14, whereas at a lower specific gravity it will sink further so that the liquid level will be disposed higher on the float, as at 14a.
Even though the liquid level is at its maximum level, if the specific gravity is below 1.3, the gauge will display a positive depth. To correct the effect of the different float buoyancy in different specific-gravity liquids, the display must be adjusted by the amount of the float "sinkage." To achieve this, an external zero offset reference input or a specific gravity adjustment is provided by the potentiometer 62. By rotating the knob of the potentiometer 62, the zero level can be adjusted, without changing the setting of the zero set potentiometer 60.
Consequently, the range is also "moved" by this same offset amount. By providing a separate potentiometer 62 for specific gravity adjustment, the float line corrections can be effected without altering the initial zero set calibration, which is used as an installation calibration.
A table may be affixed to the housing 21 showing the amount of offset (in inches) for different specific gravities, e.g., from 0.5 to 1.3. The specific gravity adjustment potentiometer 62 is turned until the value displayed on the display circuit 52 is corrected by the amount shown in the table. For example, if the liquid 13 has a specific gravity of 1.0, the corresponding offset given in a table may, e.g., be 0.2 inches. Thus, the specific gravity adjustment potentiometer 62 is turned until the display is reduced by 0.2 inches. For example, if the display 52 were displaying a level of 30.2 inches, the potentiometer 62 is adjusted until the display shows the value of 30.0 inches. The gauge is then considered adjusted for a specific gravity of 1Ø
From the foregoing, it can be seen that there has been provided an improved liquid level gauge with a calibration system which accommodates adjustment fox different specific gravities of liquids being gauged.
The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. While particular embodiments have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the broader aspects of applicant's contribution. The actual scope of the protection sought is intended to be defined in the following claims when viewed in their proper perspective based on the prior art.
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Claims (19)
1. A liquid level gauge for sensing the level of the surface of a body of liquid in a vessel, the gauge comprising:
a float member adapted to float on the surface of the liquid in a position which varies with the level of the surface, a sensing circuit coupled to the float member for sensing the position of the float member, an indicating circuit coupled to the sensing circuit for indicating the liquid level corresponding to the float position, and a calibration circuit for varying the calibration of the sensing circuit in accordance with changes in the specific gravity of the liquid so that the float member will accurately indicate the level of the liquid surface irrespective of the specific gravity of the liquid.
a float member adapted to float on the surface of the liquid in a position which varies with the level of the surface, a sensing circuit coupled to the float member for sensing the position of the float member, an indicating circuit coupled to the sensing circuit for indicating the liquid level corresponding to the float position, and a calibration circuit for varying the calibration of the sensing circuit in accordance with changes in the specific gravity of the liquid so that the float member will accurately indicate the level of the liquid surface irrespective of the specific gravity of the liquid.
2. The gauge of claim 1, wherein the calibration circuit includes a potentiometer.
3. The gauge of claim 2, wherein the potentiometer includes a control knob disposed for access by a user.
4. The gauge of claim 3, and further comprising a housing disposed externally of the vessel enclosing the indicating circuit and the calibration circuit.
5. The gauge of claim 1, wherein the sensing circuit includes a voltage divider incorporating a plurality of reed switches.
6. The gauge of claim 5, wherein the reed switches are staggered in the direction of the depth being measured.
7. The gauge of claim 1, wherein the indicating circuit includes a liquid crystal display.
8. A liquid level gauge for sensing the level of the surface of a body of liquid in a vessel, the gauge comprising:
a float member adapted to float on the surface of the liquid in a position which varies with the level of the surface, a sensing circuit coupled to the float member for sensing the position of the float member, an indicating circuit coupled to the sensing circuit for indicating the liquid level corresponding to the float position, the sensing circuit including a zero set circuit for calibrating the gauge so that the indicating circuit will indicate a zero level when the vessel is filled with a liquid of maximum specific gravity, and a specific gravity adjustment circuit coupled to the zero set circuit for varying the zero set circuit in accordance with changes in the specific gravity of the liquid so that the position of the float member will accurately indicate the level of the liquid surface irrespective of the specific gravity of the liquid.
a float member adapted to float on the surface of the liquid in a position which varies with the level of the surface, a sensing circuit coupled to the float member for sensing the position of the float member, an indicating circuit coupled to the sensing circuit for indicating the liquid level corresponding to the float position, the sensing circuit including a zero set circuit for calibrating the gauge so that the indicating circuit will indicate a zero level when the vessel is filled with a liquid of maximum specific gravity, and a specific gravity adjustment circuit coupled to the zero set circuit for varying the zero set circuit in accordance with changes in the specific gravity of the liquid so that the position of the float member will accurately indicate the level of the liquid surface irrespective of the specific gravity of the liquid.
9. The gauge of claim 8, wherein the specific gravity adjustment circuit includes a potentiometer.
10. The gauge of claim 9, wherein the potentiometer includes a control knob disposed for access by a user.
11. The gauge of claim 10, and further comprising a housing disposed externally of the vessel enclosing the indicating circuit and the zero set circuit and the specific gravity adjustment circuit.
12. The gauge of claim 8, and farther comprising a range adjustment circuit for adjusting a maximum depth level of the sensing circuit.
13. The gauge of claim 8, and further comprising a DC power supply coupled to the circuits.
14. The gauge of claim 8, wherein the zero set circuit includes a first potentiometer, and the specific gravity adjustment circuit includes a second potentiometer in series with the first potentiometer.
15. A method of calibrating a liquid level gauge in which the position of a float member floating on the surface of a liquid is sensed by a sensing circuit for indicating the corresponding level of the liquid, the method comprising:
calibrating a zero level of the sensing circuit based on a maximum specific gravity of the liquid; and adjusting the calibration in accordance with the actual specific gravity of the liquid so that the zero level is not affected by the specific gravity of the liquid.
calibrating a zero level of the sensing circuit based on a maximum specific gravity of the liquid; and adjusting the calibration in accordance with the actual specific gravity of the liquid so that the zero level is not affected by the specific gravity of the liquid.
16. The method of claim 15, wherein the adjusting includes varying a resistance in the sensing circuit.
17. The method of claim 16, and further comprising a user- accessible resistance-varying control member.
18. The method of claim 15, and further comprising displaying the sensed liquid level.
19. The method of claim 15, wherein the calibration adjusting is effected using a zero level set input to the sensing circuit.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US99756701A | 2001-11-29 | 2001-11-29 | |
| US09/997,567 | 2001-11-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2412405A1 true CA2412405A1 (en) | 2003-05-29 |
Family
ID=25544161
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2412405 Abandoned CA2412405A1 (en) | 2001-11-29 | 2002-11-25 | Liquid level gauge and specific gravity calibration therefor |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2412405A1 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105841779A (en) * | 2016-05-17 | 2016-08-10 | 中国地质科学院水文地质环境地质研究所 | Non-direct-contact type underground water level meter |
| CN112013929A (en) * | 2020-09-27 | 2020-12-01 | 中国舰船研究设计中心 | Calibration device and method for long-range magnetostrictive liquid level meter of ship oil tank |
| CN112903064A (en) * | 2021-01-21 | 2021-06-04 | 南京睿骥自动化有限公司 | High-temperature magnetic flap liquid level meter |
| CN116519101A (en) * | 2023-01-13 | 2023-08-01 | 潍坊亚峰化工仪表有限公司 | Automatic detection, calibration and correction system for wide-range liquid level meter |
-
2002
- 2002-11-25 CA CA 2412405 patent/CA2412405A1/en not_active Abandoned
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105841779A (en) * | 2016-05-17 | 2016-08-10 | 中国地质科学院水文地质环境地质研究所 | Non-direct-contact type underground water level meter |
| CN105841779B (en) * | 2016-05-17 | 2023-10-24 | 中国地质科学院水文地质环境地质研究所 | Non-direct contact type underground water level meter |
| CN112013929A (en) * | 2020-09-27 | 2020-12-01 | 中国舰船研究设计中心 | Calibration device and method for long-range magnetostrictive liquid level meter of ship oil tank |
| CN112013929B (en) * | 2020-09-27 | 2023-06-06 | 中国舰船研究设计中心 | Device and method for calibrating long-range magnetostrictive liquid level meter of ship oil tank |
| CN112903064A (en) * | 2021-01-21 | 2021-06-04 | 南京睿骥自动化有限公司 | High-temperature magnetic flap liquid level meter |
| CN112903064B (en) * | 2021-01-21 | 2023-07-25 | 南京睿骥自动化有限公司 | High-temperature type magnetic flap level gauge |
| CN116519101A (en) * | 2023-01-13 | 2023-08-01 | 潍坊亚峰化工仪表有限公司 | Automatic detection, calibration and correction system for wide-range liquid level meter |
| CN116519101B (en) * | 2023-01-13 | 2023-09-08 | 潍坊亚峰化工仪表有限公司 | Automatic detection, calibration and correction system for wide-range liquid level meter |
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