CN1292235C - Liquid level sensor - Google Patents
Liquid level sensor Download PDFInfo
- Publication number
- CN1292235C CN1292235C CNB200410092386XA CN200410092386A CN1292235C CN 1292235 C CN1292235 C CN 1292235C CN B200410092386X A CNB200410092386X A CN B200410092386XA CN 200410092386 A CN200410092386 A CN 200410092386A CN 1292235 C CN1292235 C CN 1292235C
- Authority
- CN
- China
- Prior art keywords
- electrode
- mentioned
- liquid level
- signal
- measuring
- 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.)
- Expired - Fee Related
Links
Images
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
- G01F23/26—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 capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields
- G01F23/263—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 capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields by measuring variations in capacitance of capacitors
- G01F23/266—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 capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields by measuring variations in capacitance of capacitors measuring circuits therefor
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D21/00—Measuring or testing not otherwise provided for
- G01D21/02—Measuring two or more variables by means not covered by a single other subclass
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- General Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Thermal Sciences (AREA)
- Fluid Mechanics (AREA)
- Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
Abstract
The present invention relates to a liquid level sensor capable of measuring accurately the liquid level. This liquid level sensor is equipped with a sensor part installed in a vessel, and a measuring circuit. The sensor part has a driving electrode for inputting an alternating-current signal, a measuring electrode and a reference electrode, and the reference electrode has a signal conduction part enclosed by a shield constituted of the first shield electrode, the second shield electrode and shield layers, and a reference measuring part projecting from the shield.
Description
Technical field
The present invention relates to a kind of liquid level sensor of measuring liquid level.
Background technology
In depositing the container of liquid, some has the liquid level sensor of the measuring liquid level of being used for.As liquid level sensor, for example, promising known have float-type transmitter, the hyperacoustic sensor of use and static capacity type sensor or the like.
Here, be for example high 20mm at container, under the situation of the small containers that diameter 20mm is such, in float-type transmitter, owing to have to do float for a short time, therefore the buoyancy of float self becomes too small, so there is this problem of position detection device that is not enough to support variohm, optical device, magnetic device etc. and float interlock.In addition, small containers is because volume is less, and the absolute value of liquid level also diminishes, thereby requirement is for example at the positive high measurement accuracy of negative error about 0.5mm on the short transverse.In small containers with such singularity, use hyperacoustic sensor if adopt, receive hyperacoustic distance owing to can not guarantee fully to send, cause measuring accuracy to reduce, accurately measuring liquid level.
Relative therewith, static capacity type sensor can be than float-type transmitter miniaturization more, and than using hyperacoustic sensor measuring liquid level more accurately.
In the static capacity type sensor, the measurement that a pair of part is immersed in the liquid is configured on the vertical direction of container with electrode.Here, because the inductivity in the liquid is bigger than airborne inductivity, a pair of measurement is with in the electrode, and that part of electrostatic capacitance quantitative change that is immersed in the liquid is big.Therefore, liquid level is high more, and electrostatic capacitance is just big more, if measure electrostatic capacitance, just can measure liquid level.In addition, in liquid level sensor in the past, has a pair of reference electrode that is immersed in fully in the liquid.A pair of by this with reference to using the measured electrostatic capacitance of electrode, can calculate the inductivity of the liquid under this temperature.Like this, use interelectrode electrostatic capacitance, just can improve measuring accuracy (reference example such as patent documentation 1) if use this inductivity to measure measurement
Patent documentation 1: the spy opens flat 11-108735 communique.
Yet, because a pair of measurement causes measuring the measured value generation error with the electrostatic capacitance in the electrode easily with electrode and a pair of with reference to being easy to generate electrostatic coupling between the electrode.Particularly, if with the liquid level sensor miniaturization,, can be more prone to take place error owing to measuring with electrode and reference the approaching of electrode.
Summary of the invention
The present invention is for solving above-mentioned problem in the past, and purpose is to provide a kind of liquid level sensor of measuring liquid level accurately.
The technical scheme that realizes the object of the invention is as follows:
A kind of liquid level sensor comprises: measuring-signal is supplied with electrode, and it is configured in the container of receiving fluids, the input specified signal; Potential electrode, it is configured in the above-mentioned measuring-signal of distance and supplies with electrode predetermined distance place, measures the electrostatic capacitance that changes corresponding to the height of liquid level; And reference electrode, be used to measure above-mentioned measuring-signal and supply with electrostatic capacitance between electrode and the above-mentioned potential electrode, obtain the reference point of above-mentioned electrostatic capacitance, wherein, the part of above-mentioned reference electrode is by electromagnetic screen, the shielding of above-mentioned reference electrode comprises: on above-mentioned insulating material, be arranged on first guarded electrode and the secondary shielding electrode of its both sides along above-mentioned reference electrode, and a pair of screen layer that is set to the above-mentioned insulating material of clamping.
Such liquid level sensor because the conductively-closed of a reference electrode part, the part of conductively-closed in the reference electrode, not can and potential electrode or measuring-signal supply with between the electrode and produce electrostatic coupling.This liquid level sensor by electrical specification between drive electrode and the potential electrode and the measured electrical specification of part that do not have conductively-closed in reference electrode, comes measuring liquid level.
As optimal way, in above-mentioned liquid level sensor, above-mentioned reference electrode, the front end in the signal conduction portion that is connected with metering circuit, have measure above-mentioned reference point with reference to using measurement section, above-mentioned signal conduction portion is by electromagnetic screen.
Such liquid level sensor with reference to resulting signal imports in the process in the metering circuit with measurement section, can be prevented additional noise in the stop signal.Particularly, because reference uses the measuring point near the bottom surface of container, the benchmark when therefore being easy to obtain detecting liquid level.
As optimal way, in above-mentioned liquid level sensor, cover the shielding of above-mentioned measuring-signal supply electrode, above-mentioned potential electrode, above-mentioned reference electrode and above-mentioned reference electrode with the dielectric film of water proofing property.
Contacting between such liquid level sensor, each electrode that can prevent electric conductivity and screen layer and liquid.
Such liquid level sensor because guarded electrode and screen layer are configured to surround with reference to electrode package, therefore can be consolidated the electromagnetic screen of reference electrode.
As optimal way, above-mentioned potential electrode and above-mentioned measuring-signal are supplied with distance between electrodes and are equaled first guarded electrode and above-mentioned measuring-signal supply distance between electrodes.
Such liquid level sensor can make measuring-signal supply with the signal that the electrode concussion produces, and propagates equably and gives potential electrode, guarded electrode and screen layer.
As optimal way, in the above-mentioned liquid level sensor, above-mentioned measuring-signal is supplied with electrode, above-mentioned potential electrode and above-mentioned reference electrode front position separately and is flushed.
Such liquid level sensor flushes by the front end that makes each electrode, can be from quite dark position measurement liquid level.
As optimal way, above-mentioned reference electrode have measure described reference point with reference to using measurement section, except described reference with the not conductively-closed of measurement section, all the other might be immersed in part conductively-closed in the liquid described at least reference electrode.
In this liquid level sensor, in can the scope of measuring liquid level, because except being used for obtaining the part of reference point, because reference electrode conductively-closed, even so liquid level change except that the reference point measure portion of reference electrode, can not supplied with electrode generation electrostatic coupling with measuring-signal yet.
As optimal way, in the above-mentioned liquid level sensor, above-mentioned potential electrode and above-mentioned measuring-signal supply electrode and above-mentioned reference electrode are set to adjacent to each other, and make each electrode become the rectangular membranous type that is covered by the dielectric film of long strip type.
This liquid level sensor can prevent that each electrode of electric conductivity from contacting with screen layer or liquid.In addition, owing to be long strip type, therefore install and become easier, reliably the distance between fixed electorde.
By the present invention,, therefore can prevent the part of conductively-closed and the electrostatic coupling between potential electrode or the measuring-signal supply electrode owing to shield with reference to the part of electrode.Like this, strengthen the ability of reference electrode opposing external electromagnetic noise, thereby can improve the measuring accuracy of liquid level.In addition, cover each electrode by film and be immersed in part in the liquid, be easier to install.
In addition, if except fore-end, all shield, with regard near the electrical specification the easier measuring vessel bottom surface with reference to electrode.
In addition, if make measuring-signal supply with electrode to the distance between the potential electrode, and measuring-signal supplies with electrode to the distance between the shielding about equally, just makes the propagation approximate equality of supplying with the signal of electrode from measuring-signal, thereby reduces measuring error.
In addition, if make the height of bottom surface of the relative container of front end of each electrode identical, even have only a spot of liquid so, also can measuring liquid level.
Description of drawings
Fig. 1 is the whole pie graph of the liquid level sensor in the embodiments of the present invention.
Fig. 2 is the synoptic diagram of the sensor part of explanation liquid level sensor.
Fig. 3 is the exploded perspective view of the sensor part of liquid level sensor.
Fig. 4 is a figure who measures example of the measured value of explanation liquid level sensor.
Among the figure: 2-sensor part, 3-metering circuit, 4,7-diaphragm (dielectric film); 5-the 1st dielectric film (insulating material), 6-the 2nd dielectric film (insulating material), 9, the 15-screen layer; the 10-potential electrode, 10a, 11a, 13a-lower end (front end), 11-drive electrode (measuring-signal supply electrode); 12-the 1st guarded electrode; the 13-reference electrode, 14-the 2nd guarded electrode, 25-is with reference to using measurement section; r1, r2-distance, the h0-reference position.
Embodiment
The contrast accompanying drawing is elaborated to implementing best mode of the present invention below.
As shown in Figure 1, the liquid level sensor in the present embodiment comprises the sensor part 2 that is fixed in the container 1, and the metering circuit 3 that is electrically connected with sensor part 2.
As Fig. 2 and shown in Figure 3, sensor part 2 is elongated film like, is connected with metering circuit 3 according to the cardinal extremity 2a of long side direction one side, and front end 2b is positioned near the bottom surface of container 1 fixing like that.In addition, to the front end 2b, the width of sensor part 2 broadens from cardinal extremity 2a.Preferably make from the front end of this width expansion 8 beginnings and be immersed in the liquid.
Be positioned on the outermost diaphragm 4 of a certain side, with the laminar screen layer 9 that is provided with about half of width that width is a diaphragm 4.The 1st dielectric film 5 is close on the diaphragm 4, with diaphragm 4 clamping screen layers 9.On the 1st dielectric film 5, roughly dispose potential electrode 10, drive electrode (measuring-signal supply electrode) the 11, the 1st guarded electrode 12, reference electrode the 13, the 2nd guarded electrode 14 of each wire side by side along the certain distance in long side direction interval of the 1st dielectric film 5.The 2nd dielectric film 6 by driving fit on the 1st dielectric film 5, with each electrode 10,11,12,13,14 of the 1st dielectric film 5 clampings.On the 2nd dielectric film 6, with the laminar screen layer 15 that is provided with about half of width that width is the 2nd dielectric film 6.In addition, diaphragm 7 by driving fit on the 2nd dielectric film 6, with the 2nd dielectric film 6 clamping screen layers 15.
In addition; as shown in Figure 2, the 2nd dielectric film 6 and diaphragm 7, shorter in the cardinal extremity 2a of sensor part 2 side than diaphragm 4 and the 1st dielectric film 5; in the cardinal extremity 2a on the top that is equivalent to sensor part 2 side, each electrode 10,11,12,13,14 exposes with the length of regulation respectively.
As Fig. 2 and shown in Figure 3, vicinity from the cardinal extremity to the front end on the face 17 that drive electrode 11 is set at the 1st dielectric film 5 with the live width and the thickness of regulation.The upper end of this drive electrode 11 is connected with the metering circuit 3 (with reference to figure 1) of the cardinal extremity 2a side that is positioned at sensor part 2, is transfused to the driving AC signal of regulation.In addition, the lower end of drive electrode 11 (front end) 11a is positioned at the top of the front end 5a of the 1st dielectric film 5, the front end 5a of distance the 1st dielectric film 5 for regulation apart from r1.
This potential electrode 10 forms capacitor element with drive electrode 11.Its electrostatic capacitance value is by surface area, interelectrode distance and the inductivity decision of potential electrode 10 with drive electrode 11.The inductivity of relative air, the inductivity of liquid is very big.Therefore, the electrostatic capacitance between potential electrode 10 and the drive electrode 11, roughly be immersed in subsurface surface area, also promptly be directly proportional to the length the liquid level described later with the lower end of drive electrode 11 from potential electrode 10.
In addition, on face 17, it is on the roughly symmetrical position of benchmark and potential electrode 10 that the 1st guarded electrode 12 is set at drive electrode 11.Also promptly, the distance between distance between drive electrode 11 and the potential electrode 10 and drive electrode 11 to the 1st guarded electrodes 12 is roughly the same.The upper end ground connection of the 1st guarded electrode 12.In addition, the lower end of the 1st guarded electrode 12 (front end) 12a is positioned at the top of the front end 5a of the 1st dielectric film 5, the distance the 1st dielectric film 5 front end 5a for the regulation apart from r2.And apart from r2 greater than distance r1.
The 2nd guarded electrode 14 is set on the face 17, clips reference electrode 13 jointly with the 1st guarded electrode 12.Also promptly, the distance between reference electrode 13 to the 2nd guarded electrodes 14, and the distance between reference electrode 13 to the 1st guarded electrodes 12 is about equally.The upper end ground connection of the 2nd guarded electrode 14.In addition, the lower end of the 2nd guarded electrode 14 (front end) 14a is positioned at the top of the front end 5a of the 1st dielectric film 5, the distance the 1st dielectric film 5 front end 5a for the regulation apart from r2.
In addition, screen layer 9 is set at guarded electrode 12,14 and screen layer 15 and overlaps the place.Specifically, the width of the screen layer 15 interelectrode distance that is substantially equal to guarded electrode 12 and 14 adds the width of each guarded electrode 12,14.In addition, the lower end of screen layer 9 (front end) is the same with guarded electrode 12,14, is positioned at the top of the front end of the 1st dielectric film 5 and the 2nd dielectric film 6, the front end of distance the 1st dielectric film 5 and the 2nd dielectric film 6 for regulation apart from r2.Here, screen layer 9 is made by conductive material.Through being formed on the conduction perforated portion 20 on the 1st dielectric film 5, be electrically connected with the 2nd guarded electrode 14.In addition, conduction perforated portion 20 for example can form by the material of plating electric conductivity for the perforation that is formed on the 1st dielectric film 5.
In addition, each electrode 10,11,12,13,14 and screen layer 9,15 are by on the film 4,5,6 of the conductive material that is fitted with specific thickness, with partly etching and forming of conductive material.In addition, on the width expansion 8 of sensor part 2, it is big that the configuration space between each electrode 10,11,12,13,14 also is with the 1st guarded electrode 12 that the center correspondingly becomes.
As shown in Figure 1, metering circuit 3 has the oscillating circuit 31 that for example produces square wave ac signal.This oscillating circuit 31 comprises 3 reversers, 32,33,34 series circuits that constituted, resistor 35 that is connected with the input end and the output terminal of this series circuit and the capacitor 36 that is connected with the output terminal of the input end of reverser 32 and reverser 33.The output terminal of series circuit is connected with the drive electrode 11 of sensor part 2.
In addition, metering circuit 3 has resistor 37 and the analog switch 38 that is connected with an end of potential electrode 10.In addition, metering circuit 3 has resistor 39 and the analog switch 40 that is connected with an end of reference electrode 13. Resistor 37,39 other end separately is ground connection respectively. Analog switch 38,40 is connected with low-pass filter 41.In addition, analog switch 38,40 control end separately is connected with oscillating circuit 31, according to the output waveform of oscillating circuit 31, switches between the ON of switch or OFF.
Low-pass filter 41 has capacitor 42 and the resistor 43 that an end is connected with analog switch 38, and the other end of resistor 43 is connected with capacitor 44, resistor 45 and capacitor 46.In addition, low-pass filter 41 has capacitor 47 and the resistor 48 that an end is connected with analog switch 40, and the other end of resistor 48 is connected with capacitor 49, resistor 50 and capacitor 46.The output of this low-pass filter 41 is connected with differential amplifier circuit 51.In addition, capacitor 42,47, capacitor 44,49, resistor 45,50 other end difference ground connection separately.Capacitor 46 is connected across between the resistor 43 and resistor 48 other end separately.
The non-inverting input of operational amplifier 53 is connected with the output of reference electrode 13 sides of low-pass filter 41.Between the output terminal of this operational amplifier 53 and the inverting input also cross-over connection resistor 59 is arranged.In addition, the output terminal of operational amplifier 53 is connected respectively with resistor 60 and resistor 61.Resistor 60 ground connection, resistor 61 is connected with the non-inverting input of operational amplifier 54.
The output terminal of operational amplifier 54 is connected with an end of resistor 62.This resistor 62 is connected with other control circuits, from exporting here corresponding to the signal from reference position h0 to the distance the liquid level (liquid level).In addition, between the inverting input of the other end of this resistor 62 and operational amplifier 54, be parallel with resistor 63 and capacitor 64.
Next, the action to this liquid level sensor describes.In addition, the inner face of the container shown in Fig. 11 is fixed with sensor part 2.Here, preferably make the length direction of each electrode 10,11,12,13,14 of sensor part 2 consistent, and the front end of sensor part 2 contact with the bottom surface of container 1 with the vertical direction of container 1.
At first, in container 1, as shown in Figure 2, add the liquid that highly equals apart from r2 (reference position h0).Under this state, oscillating circuit 31 produces to drive uses AC signal, and inputs to drive electrode 11.AC signal is a media with air and liquid, propagates into potential electrode the 10, the 1st guarded electrode 12, screen layer 9,15 and reference measurement section 25 from drive electrode 11.In addition, because the 1st guarded electrode 12 and screen layer 9,15 ground connection, in the reference electrode 13, can transmitting signal in the signal conduction portion 26.
In the potential electrode 10, because the propagation of signal, producing corresponding to the electrostatic capacitance based on the inductivity of liquid, also is the reception voltage (received signal) of liquid level.This reception voltage is transfused to the analog switch 38 to metering circuit 3.In addition, with reference to in the measurement section 25, because the propagation of signal, produce corresponding to reception voltage (received signal) based on the electrostatic capacitance of the inductivity of liquid.This reception voltage is transfused to the analog switch 40 to metering circuit 3.
Here, because analog switch 38,40, corresponding to the driving interchange of oscillating circuit 31, the closure of change-over switch disconnects, so the reception voltage of the reception voltage of the reception voltage of potential electrode 10 and reference electrode 13 is by synchronous detection.Each of 38,40 synchronous detections of analog switch receives voltage and is transfused to low-pass filter 41, removes unnecessary alternating component, takes out flip-flop.Further be transfused to difference discharge circuit 51, after the amplification, output and the reception voltage of potential electrode 10 deduct the signal that the resulting difference of reception voltage as the reference electrode 13 of reference point is directly proportional.In addition, potential electrode 10 and drive electrode 11 are immersed in the inductivity between the part in the liquid, with potential electrode 10 and reference electrode 13 with reference to identical with the inductivity between the measurement section 25.
Further, the amount of the liquid in container 1 increases, and liquid level rises to above after the h0 of reference position, the increase that roughly is directly proportional with liquid level of drive electrode 11 and electrostatic capacitance between the potential electrode 10.Relative therewith, reference electrode 13 is because it surpasses part conductively-closed electrode 12,14 and screen layer 9,15 shieldings of reference position h0, so its electrostatic capacitance can the electrostatic capacitance when being equivalent to reference position h0 not begin to change.As mentioned above, the output of sensor, and corresponding to the signal of the electrostatic capacitance of potential electrode 10 sides be directly proportional corresponding to the difference between the signal of the electrostatic capacitance of reference electrode 13 sides.Therefore, if liquid level rises, just the increase that is directly proportional with it.
In addition, the zone more than the h0 of reference position is if liquid level descends, just the electrostatic capacitance value between drive electrode 11 and the potential electrode 10 reduces.Relative therewith, the zone more than the h0 of reference position, even liquid level descends, the electrostatic capacitance value between drive electrode 11 and the reference electrode 13 can not change yet.Therefore, if liquid level descends, just the output of sensor direct ratio minimizing thereupon.
Like this, the output of sensor just becomes with reference to being benchmark with the reception voltage of measurement section 25, the big or small signal that roughly is directly proportional with liquid level.So, can learn the absolute value of liquid level according to the stool and urine of signal.
(embodiment)
Shown among Fig. 4 that liquid level that the liquid level sensor that uses the structure shown in Fig. 2 is surveyed and of the relation between the electrostatic capacitance value measure example.Employed sensor part 2 in the measurement is used the made film 4,5,6,7 of liquid crystal polymer, and its thickness is 25 μ m, and width is about 11mm, and length is 50mm.Each electrode 10,11,12,13,14 is a copper, and width is about 1mm, and thickness is 125 μ m.In addition, the distance between the center of the center of drive electrode 11 and potential electrode 10 is about 1.8mm, and the distance between the center of the center of drive electrode 11 and the 1st guarded electrode 12 is about 1.8mm.In addition, the distance between the center of the center of drive electrode 11 and reference electrode 13 is about 3.6mm.Reference electrode 13 is about 1mm from guarded electrode 12,14 outstanding length.Be about 0.5mm from lower end 10a, 11a, the 13a of drive electrode 11 and potential electrode 10 and reference electrode 13 to the distance the front end 2b of sensor part 2.
Liquid level with the pure water in the liquid level sensor measuring vessel 1 of above-mentioned formation.In addition, make the front end 2b of sensor part 2 be positioned at the bottom surface of container 1, the cardinal extremity 2a of sensor part 2 is towards the upper side of container 1, almost vertically is installed on container 1 inner face and measures.
Among Fig. 4, the longitudinal axis is an electrostatic capacitance value, and transverse axis is a liquid level.Liquid level is-and during 10mm, the expression container is in empty state, and during for 0mm, the expression liquid level is equivalent to the reference position h0 shown in Fig. 2.In addition, line L1 represents the variation of the electrostatic capacitance value between drive electrode 11 and the potential electrode 10.Line L2 represents the variation of the reference of drive electrode 11 and reference electrode 13 with the electrostatic capacitance value between the measurement section 25.
Shown in line L2, the electrostatic capacitance value between drive electrode 11 and the reference electrode 13 during from 0mm to 55mm, is about 0.5pF in liquid level.Relative therewith, shown in line L1, the electrostatic capacitance between drive electrode 11 and the potential electrode 10 is in liquid level during from 0mm to 55mm, with the increase of the liquid level increase that roughly is directly proportional.So, by measuring the value of electrostatic capacitance separately, measuring liquid level accurately just.In addition, when liquid level was 0mm, the value of the electrostatic capacitance of the line L2 why value than the electrostatic capacitance of line L1 was also little, be because drive electrode 11 to the distance between the reference electrode 13, than drive electrode 11 to the distance between the potential electrode 10.
According to this embodiment, measure with reference to exposing owing to have only in the reference electrode 13 with the part of electrostatic capacitance, and be immersed into other parts (downside of width extension 8 among Fig. 2) conductively-closed in the liquid, therefore can measure the electrostatic capacitance value that uses as benchmark accurately.In addition, do not have the part of conductively-closed,, be set near the bottom surface of end portion near container 1 of reference electrode 13 yet, therefore be easier to measure the electrostatic capacitance of using as benchmark promptly with reference to measurement section 25.So, even liquid measure is seldom, also measuring liquid level accurately.Here, to arrive the distance of reference position h0 tries to achieve as liquid level, because reference position h0 is by the known value that installation site determined of liquid level sensor in container 1, therefore can obtain simply from the bottom surface of container 1 to the absolute value of the distance the liquid level.
In addition, potential electrode 10 and reference electrode 13 common drive electrodes 11 are come measuring liquid level by 3 electrodes, therefore can make the liquid level sensor miniaturization.In addition, electrode 10,11,13 is owing to covered by the low film 4,5,6,7 of water-intake rate, thereby can prevent contacting between electrode 10,11,13 and the liquid.
In addition, sensor part 2, owing to making film 4,5,6,7 laminations form rectangular membranous type, therefore easier to mount.Distance between particularly a plurality of electrodes 10,11,12,13,14 is easier to keep often certain.In addition, because the shielding of reference electrode 13 is three-dimensional, therefore can approximately all shield in week entirely with reference to the signal conduction portion 26 of electrode 13.So, when liquid level is higher than reference position h0, can shield reference electrode 13 reliably, improve the measuring accuracy of liquid level.In addition, by adjusting the length of shielding, can adjust reference position h0.
In addition, because drive electrode 11 is to the distance between the potential electrode 10, and drive electrode 11 is roughly the same to the distance between ground 1 guarded electrode 12, therefore can make the AC signal approximate equality ground that is carried on the drive electrode 11 propagate the electrode 10,12 of giving other, prevents the generation of measuring error.
In addition, suitable example as this liquid level sensor, can be used in the fuel cell that drive source developed as the power supply of mobile terminal devices such as PDA (palm notepad), computing machine, mobile phone or vehicle, perhaps be used in the memory space (residual volume) of container of the container of detection of stored fuel or storage waste liquid.Owing to can pass through reference electrode 13 measuring basis electrostatic capacitance value accurately,, also can detect liquid level reliably even therefore in container, be injected under the situation of pure methyl alcohol or the formic acid liquid different with the inductivitys such as mixed liquor of formaldehyde.In addition, this liquid level sensor can also be applied to store in the containers such as washing machine, dish-washing machine, grill pan, bathtub in the equipment of liquid such as water.
Here, because therefore liquid level sensor measuring basis electrostatic capacitance value accurately can detect reference position h0 reliably.In addition, by the output of liquid level sensor, can easily calculate the ratio of liquid level and reference position h0.Like this, if liquid level reaches reference position h0 (above-mentioned ratio is 1), control thereby can give a warning.In addition, when liquid level sensor is installed in the hold-up vessel of waste liquid etc., owing to can easily judge whether liquid level reaches assigned position, thereby can before storage tank overflows, gives a warning and control by the output valve of sensor.
In addition, the present invention is not limited in above-mentioned embodiment, can also use widely.
For example, can be used as electrode area in having the impedance of utilizing and the being immersed in liquid this point that is directly proportional, measure impedance, thereby detect the metering circuit of the current detection circuit and the voltage detecting circuit of liquid level as the upperseat concept of electrostatic capacitance.
In addition, in the metering circuit 3, between analog switch 38,40 and oscillating circuit 31,90 ° phase-shift circuit 70 (with reference to figure 1) can the cross-over connection signal have misplaced.Because the big phase bit position of signal intensity of reception voltage that can be by 90 ° of the relative drive waveforms of phase place dislocation carries out data processing, thereby can realize further high sensitivityization.
In addition, in the film 4,5,6,7, can only make outermost diaphragm 4,7 be no absorptive material; perhaps almost there is not absorptive material, in addition, can be by outside surface coated glass at film; perhaps, prevent suction by further covering other waterproof materials.
In addition, between the guarded electrode 12,14, the driving electrode of reference electrode 13 can also be set.This driving electrode and drive electrode 11 can be connected on the identical oscillating circuit 31, come measuring liquid level by two pairs of electrodes.
Claims (7)
1, a kind of liquid level sensor,
Comprise:
Measuring-signal is supplied with electrode, and it is configured in the container of receiving fluids, the input specified signal;
Potential electrode, it is configured in the above-mentioned measuring-signal of distance and supplies with electrode predetermined distance place, measures the electrostatic capacitance that changes corresponding to the height of liquid level; With
Reference electrode is used to measure the electrostatic capacitance between above-mentioned measuring-signal supply electrode and the above-mentioned potential electrode, obtains the reference point of above-mentioned electrostatic capacitance,
Wherein, the part of above-mentioned reference electrode is by electromagnetic screen,
It is characterized in that above-mentioned reference electrode is set on the insulating material;
The shielding of above-mentioned reference electrode comprises: on above-mentioned insulating material, be arranged on first guarded electrode and the secondary shielding electrode of its both sides along above-mentioned reference electrode, and a pair of screen layer that is set to the above-mentioned insulating material of clamping.
2, liquid level sensor according to claim 1 is characterized in that,
Above-mentioned reference electrode has with reference to using measurement section, and this measures above-mentioned reference point with reference to the front end of measurement section in the signal conduction portion that is connected with metering circuit,
Above-mentioned signal conduction portion is by electromagnetic screen.
3, liquid level sensor according to claim 1 is characterized in that,
Dielectric film with water proofing property covers the shielding that above-mentioned measuring-signal is supplied with electrode, above-mentioned potential electrode, above-mentioned reference electrode and above-mentioned reference electrode.
4, liquid level sensor according to claim 3 is characterized in that,
Above-mentioned potential electrode and above-mentioned measuring-signal are supplied with distance between electrodes and are equaled first guarded electrode and above-mentioned measuring-signal supply distance between electrodes.
5, liquid level sensor according to claim 1 is characterized in that:
Above-mentioned measuring-signal is supplied with electrode, above-mentioned potential electrode and above-mentioned reference electrode front position separately and is flushed.
6, liquid level sensor according to claim 1 is characterized in that,
Above-mentioned reference electrode have measure described reference point with reference to using measurement section, except described reference with the not conductively-closed of measurement section, all the other might be immersed in part conductively-closed in the liquid described at least reference electrode.
7, liquid level sensor according to claim 1 is characterized in that,
Above-mentioned potential electrode and above-mentioned measuring-signal are supplied with electrode and above-mentioned reference electrode, are set to adjacent to each otherly, and each electrode are become by the rectangular membranous type that dielectric film covered of long strip type.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2003383340 | 2003-11-13 | ||
| JP2003383340A JP2005147779A (en) | 2003-11-13 | 2003-11-13 | Liquid level sensor |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1616933A CN1616933A (en) | 2005-05-18 |
| CN1292235C true CN1292235C (en) | 2006-12-27 |
Family
ID=34692090
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB200410092386XA Expired - Fee Related CN1292235C (en) | 2003-11-13 | 2004-11-10 | Liquid level sensor |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JP2005147779A (en) |
| KR (1) | KR100675543B1 (en) |
| CN (1) | CN1292235C (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2892509B1 (en) * | 2005-10-26 | 2007-12-21 | Inergy Automotive Systems Res | CAPACITIVE GAUGE FOR FUEL TANK |
| GB0706382D0 (en) * | 2007-04-02 | 2007-05-09 | Huntleigh Technology Plc | Fluid level sensor |
| JP5778024B2 (en) * | 2011-12-27 | 2015-09-16 | 愛三工業株式会社 | Sensor device |
| JP5923349B2 (en) * | 2012-03-14 | 2016-05-24 | 矢崎総業株式会社 | Capacitive liquid level sensor |
| DE102013005963A1 (en) * | 2013-04-09 | 2014-10-09 | Balluff Gmbh | Capacitive level sensor |
| US10466090B2 (en) * | 2016-08-17 | 2019-11-05 | KSR IP Holdings, LLC | Capacitive fluid level sensor for rapid response |
| CN107884027B (en) * | 2016-09-30 | 2021-04-20 | 佛山市顺德区美的电热电器制造有限公司 | A cooking utensil that is used for cooking utensil's anti-overflow detection device and has it |
| JP6581963B2 (en) * | 2016-12-27 | 2019-09-25 | 本田技研工業株式会社 | Liquid level detection device and fuel cell system |
| IT201700082500A1 (en) * | 2017-07-20 | 2019-01-20 | Eltek Spa | DEVICE FOR DETECTION OF THE LEVEL OF A MEDIA |
| GB2579794B (en) | 2018-12-13 | 2021-05-19 | Charles Austen Pumps Ltd | A capacitive liquid level sensor and liquid sensor assembly |
| CN110231071B (en) * | 2019-07-17 | 2020-08-11 | 湖北保乾科技有限公司 | Liquid level measuring device based on capacitive sensor |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61233323A (en) * | 1985-04-08 | 1986-10-17 | Nippon Kagaku Kikai Seizo Kk | Method for measuring solution level |
| JP3422355B2 (en) * | 1997-09-22 | 2003-06-30 | 理化工業株式会社 | Capacitance type level measuring device |
| JP3436117B2 (en) | 1998-02-26 | 2003-08-11 | 理化工業株式会社 | Capacitance type level measuring device |
| JPH11311561A (en) | 1998-04-27 | 1999-11-09 | Wako:Kk | Water level sensor |
| DE10047594A1 (en) | 2000-09-26 | 2002-04-18 | Siemens Ag | Method and device for determining the level of a liquid in a container |
-
2003
- 2003-11-13 JP JP2003383340A patent/JP2005147779A/en not_active Withdrawn
-
2004
- 2004-11-08 KR KR1020040090276A patent/KR100675543B1/en not_active IP Right Cessation
- 2004-11-10 CN CNB200410092386XA patent/CN1292235C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| KR20050046554A (en) | 2005-05-18 |
| JP2005147779A (en) | 2005-06-09 |
| KR100675543B1 (en) | 2007-01-29 |
| CN1616933A (en) | 2005-05-18 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN1292235C (en) | Liquid level sensor | |
| AU2005271971B2 (en) | Proximity sensor for sensing fluid level in a container | |
| US9243941B2 (en) | Magnetic-inductive flowmeter with an empty tube detecting device of an admittance measuring type | |
| CN1503899A (en) | Method and device for measuring liquid level | |
| KR100794945B1 (en) | Liquid surface level sensor | |
| CN202109942U (en) | Novel flow measuring device for measuring flow of sewage of open channel | |
| KR100675542B1 (en) | Liquid surface level sensor | |
| AU2022228113B2 (en) | Liquid Level Measurement Apparatus | |
| KR101838935B1 (en) | Water level sensing system of apparatus | |
| KR101568376B1 (en) | Water level sensor and water level sensing system of apparatus using same | |
| KR100970402B1 (en) | Capacive liquid level detector for direct methanol fuel cell systems | |
| JP2005172757A (en) | Liquid level sensor | |
| CN218330148U (en) | Ultrasonic liquid level device | |
| JP2014092453A (en) | Sensor device | |
| KR101816636B1 (en) | Water level sensing system of apparatus | |
| CN220829260U (en) | Continuous water level detecting device | |
| AU2011232765A1 (en) | Proximity sensor for level sensing in a bilge | |
| JPS6183916A (en) | Liquid level detection method and apparatus |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| C17 | Cessation of patent right | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20061227 Termination date: 20111110 |