WO2014114259A1 - 数字液位传感器 - Google Patents

数字液位传感器 Download PDF

Info

Publication number
WO2014114259A1
WO2014114259A1 PCT/CN2014/071351 CN2014071351W WO2014114259A1 WO 2014114259 A1 WO2014114259 A1 WO 2014114259A1 CN 2014071351 W CN2014071351 W CN 2014071351W WO 2014114259 A1 WO2014114259 A1 WO 2014114259A1
Authority
WO
WIPO (PCT)
Prior art keywords
liquid level
level sensor
switch
float
magnetic
Prior art date
Application number
PCT/CN2014/071351
Other languages
English (en)
French (fr)
Inventor
迪克·詹姆斯·G
薛松生
Original Assignee
江苏多维科技有限公司
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 江苏多维科技有限公司 filed Critical 江苏多维科技有限公司
Priority to EP14742929.4A priority Critical patent/EP2950060B1/en
Priority to US14/763,431 priority patent/US11035716B2/en
Priority to JP2015554042A priority patent/JP6215961B2/ja
Publication of WO2014114259A1 publication Critical patent/WO2014114259A1/zh

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
    • G01F23/30—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 floats
    • G01F23/56—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 floats using elements rigidly fixed to, and rectilinearly moving with, the floats as transmission elements
    • G01F23/62—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 floats using elements rigidly fixed to, and rectilinearly moving with, the floats as transmission elements using magnetically actuated indicating means
    • 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
    • G01F23/30—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 floats
    • G01F23/64—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 floats of the free float type without mechanical transmission elements
    • G01F23/72—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 floats of the free float type without mechanical transmission elements using magnetically actuated indicating means
    • G01F23/74—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 floats of the free float type without mechanical transmission elements using magnetically actuated indicating means for sensing changes in level only at discrete points
    • 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
    • G01F23/30—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 floats
    • G01F23/64—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 floats of the free float type without mechanical transmission elements
    • G01F23/72—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 floats of the free float type without mechanical transmission elements using magnetically actuated indicating means

Definitions

  • the invention relates to a sensor for measuring liquid level, in particular to a high precision tunnel magnetoresistance (TMR) A digital level sensor that implements digital signal output from switches and encoders.
  • TMR tunnel magnetoresistance
  • Liquid level sensors are widely used in petroleum, chemical, electric power, environmental protection and other fields. Continuous measurement of liquid or phase interfaces in various openings or pressurized vessels, also for alarm and control of liquid or phase interfaces .
  • the reed pipe liquid level sensor and the Hall type liquid level sensor are more widely used.
  • the reed pipe liquid level sensor is simple in structure and low in price, and can be applied to limit, counting, etc.
  • the working principle is that the magnetic float moves up and down with the change of the liquid level, and the generated magnetic field changes cause the reed switch to act.
  • One type of structure of this type of sensor is that when the magnetic float floats to the height of a reed switch, the reed switch in the reed switch is closed by the action of an external magnetic field, forming a complete closed circuit.
  • the magnetic float is away from the reed switch, the magnetic field is removed and the magnetic reeds are separated by their own elasticity, causing the circuit to break.
  • the transmitter in the system produces a correspondingly sized current signal. By detecting the generated current signal, the height of the measured liquid level can be judged.
  • the reed switch liquid level sensor often has an individual switch that is disconnected and not broken, resulting in a false liquid level, and because of the large size of the reed switch, the resolution frequency of the sensor is limited.
  • the sensor is affected by impact, wear and vibration, the glass case inside the sensor is easily broken, which also makes the sensor difficult to install and solder. Further, when there are inductive and capacitive loads, the life of the sensor is affected.
  • the output of the reed switch liquid level sensor is an analog signal with poor anti-interference ability, so further digital processing circuits are needed to process the analog signal into a digital signal.
  • the Hall-type liquid level sensor works in the same way as the reed switch liquid level sensor. It only replaces the reed switch with a switch-type Hall plate. Its size is smaller than that of the reed switch, it is easy to install and solder, and its output. The signal is after A/D The converted digital signal has strong anti-interference ability. However, because the Hall element consumes a lot of power, it is a milliampere level, and the switching point also reaches several tens of gauss. This liquid level sensor needs frequent maintenance and replacement, which increases the cost of use.
  • the object of the present invention is to overcome the above problems existing in the prior art and to provide a novel, advanced and reliable digital liquid level sensor.
  • the invention utilizes a tunnel magnetoresistive switch to generate an action under the action of an external magnetic field, and transmits its state in the form of high and low level to the encoder connected thereto, and then supplies the digital signal to the data bus through the encoder, thereby realizing Accurately and quickly determine the height of the measured liquid level.
  • a digital liquid level sensor that converts a measured liquid level into a digital signal output, the digital liquid level sensor comprising the following parts:
  • a float floating in the liquid the float being placed adjacent to the non-magnetic conduit, The float moves up and down along the axial direction of the non-magnetic conduit as the liquid level changes;
  • At least one tunnel magnetoresistive switch that can be closed or opened by a magnetic field generated by the permanent magnet, the permanent magnet generating a magnetic field having a sufficient amplitude and direction to be at the same level as the permanent magnet
  • One or more tunnel magnetoresistive switches are closed or open;
  • At least one encoder that generates a unique code for each position of the float
  • One or more printed circuit boards sealed in the non-magnetic conduit, the tunnel magnetoresistive switch, the encoder, the data bus, the power terminal, and the ground terminal are mounted on the printed circuit board Connected and connected to each other.
  • the non-magnetic conduit has an axial length of 10 to 12000 mm and an outer diameter of 12 to 40 mm.
  • the float has a width of 10 to 200 mm and a height of 10 to 200 mm.
  • the magnetization direction of the permanent magnet is parallel to the axial direction of the non-magnetic conduit
  • the tunnel magnetoresistive switch is a tunnel magnetoresistance all-pole switch or Tunnel magnetoresistance A single pole switch with a sensitive direction parallel to the axial direction of the non-magnetic conduit.
  • the magnetization direction of the permanent magnet is perpendicular to the axial direction of the non-magnetic conduit
  • the tunnel magnetoresistive switch is a tunnel magnetoresistance all-pole switch, Tunnel magnetoresistance Bipolar switch or tunnel magnetoresistance Unipolar switch and its sensitive direction is perpendicular to the axial direction of the non-magnetic conduit.
  • the non-magnetic conduit is placed coaxially with the float, the inner diameter of the float being larger than the outer diameter of the non-magnetic conduit.
  • the tunnel magnetoresistive switches are equally spaced on the printed circuit board.
  • the encoder is a priority encoder.
  • each of said encoders has 2 N different inputs, N different outputs, and N is a natural number.
  • the position of the float is numbered 0, 1, ..., 2 N -1 indicates that N is a natural number, and the number is linearly proportional to the height of the liquid surface.
  • the encoder is a dedicated ASIC, FPGA, CPLD Or other programmable logic devices to minimize the number of components on the printed circuit board.
  • said data bus has a width of at least N bits and N is a natural number.
  • the tunnel magnetoresistive switches are electrically connected to respective input interfaces of the encoder.
  • the output interface of the encoder is electrically coupled to a corresponding interface on the data bus.
  • the printed circuit board is a flexible printed wiring board.
  • the encoder and the tunnel magnetoresistive switch are placed on a plurality of small rigid printed circuit boards interconnected by a flexible printed wiring board.
  • the small rigid printed circuit boards mentioned herein and elsewhere are defined as relatively large rigid printed circuit boards and can be small in size as long as they are guaranteed It can accommodate the tunnel magnetoresistive switch, encoder, data bus, power terminal and ground terminal.
  • a digital liquid level sensor comprising:
  • a float located outside the non-magnetic conduit and axially movable along the non-magnetic conduit
  • the non-magnetic conduit further includes:
  • a switching unit comprising at least one tunnel magnetoresistive switch that is closed or opened by a magnetic field generated by the permanent magnet
  • An encoding unit includes at least one encoder, the input of the encoding unit receiving an on-off signal from the tunnel magnetoresistive switch and outputting a digital signal characterizing the position of the float.
  • the level sensor comprises 2 N
  • the tunnel magnetoresistive switches are arranged along the axial direction of the non-magnetic conduit and are known along the axial direction of the non-magnetic conduit.
  • the present invention uses a tunnel magnetoresistive switch to detect the position of the float, and uses a priority encoder to encode the switching signal from the tunnel magnetoresistive switch.
  • the invention has the following beneficial effects: small volume, low cost, low power consumption, high reliability, high sensitivity, high resolution, long service life, strong anti-interference ability, and direct digital signal output.
  • Embodiment 1 is a schematic structural view of a liquid level sensor according to Embodiment 1 of the present invention.
  • FIG. 2 is a schematic view showing another structure of a liquid level sensor according to Embodiment 1 of the present invention.
  • FIG. 3 is a schematic diagram showing the connection of a tunnel magnetoresistive switch and a priority encoder according to Embodiment 2 of the present invention.
  • FIG. 4 is a schematic diagram showing the connection of a tunnel magnetoresistive switch and a priority encoder according to Embodiment 3 of the present invention.
  • Figure 5 is a schematic diagram of the tunnel magnetoresistance single-pole switching signal.
  • Figure 6 is a schematic diagram of the tunnel magnetoresistance bipolar switch signal.
  • Figure 7 is a schematic diagram of the tunnel magnetoresistance all-pole switching signal.
  • FIG. 1 and Figure 2 A schematic structural view of a liquid level sensor 100, 200 according to Embodiment 1 of the present invention is shown, which schematically shows a tunnel magnetoresistance switch unit 3 and an encoder 4 A digital level sensor that implements digital signal output.
  • the sensor includes a non-magnetic conduit 1 that is fixed relative to the container to be tested, one that floats in the liquid 11 and along the non-magnetic conduit 1 The float whose outer surface slides up and down as the liquid level changes.
  • the non-magnetic conduit 1 has a circular outer cross-sectional profile, and the non-magnetic conduit 1 and the float 2 have the same central axis.
  • Non-magnetic conduit 1 A printed circuit board 5 is mounted, preferably a flexible printed circuit board.
  • a tunnel magnetoresistive switch unit 3 an encoder 4, a data bus 9 and a power terminal 7 and a ground terminal 8 are mounted on the printed circuit board 5 . Encoders and magnetoresistive switches can also be mounted on multiple small rigid printed circuit boards, connected to each other by flexible printed circuit boards or electrical wiring. Tunnel magnetoresistive switch unit 3 A plurality of tunnel magnetoresistive switches are included, each tunnel magnetoresistive switch having a defined position in the non-magnetic conduit.
  • the tunnel magnetoresistive switch at substantially the same liquid level produces a sufficiently large and directional magnetic field required for the action, and the magnetization direction 12 inside the permanent magnet 6 can be aligned with the axial direction of the non-magnetic conduit 1 13 Parallel, as shown in Figure 1, can also be perpendicular to the axial direction 13 of the non-magnetic conduit 1, as shown in Figure 2.
  • Each output of the tunnel magnetoresistive switch unit 3 and the encoder 4 The corresponding input interfaces are electrically connected in sequence, and the output interface of the encoder 4 is electrically connected to the corresponding interface of the data bus 9 in turn, and the output terminal 14 is enabled.
  • the encoder 4 encodes each input from the switching unit 3 to output a digital signal to the data bus, and the height of the liquid level can be determined based on the output digital signal. For 2 N A tunnel magnetoresistive switch with a data bus width of at least N bits.
  • the non-magnetic conduit 1 preferably has the following characteristics, for example, 12 to 40 mm, depending on the environment in which the liquid level sensor is used and the conditions of use.
  • the outer diameter, 10 ⁇ 12000 mm axial length, can be either a straight tube or a curved tube.
  • the material can be made of corrosion-resistant metal, alloy or durable engineering plastic.
  • the float 2 is disposed coaxially with the non-magnetic conduit 1, and the inner diameter of the float 2 is larger than the outer diameter of the non-magnetic conduit 1.
  • Float 2 The width is preferably 10 to 200 mm, and the height is preferably 10 to 200 mm.
  • the permanent magnet 6 is fixed, and the permanent magnet 6 is driven to move up and down along the axial direction of the non-magnetic conduit 1 with the change of the liquid level.
  • the permanent magnet 6 may be fixed in the float 2 or may be fixed outside the float 2.
  • Each of the tunnel magnetoresistive switches S0, S1, ... in the tunnel magnetoresistive switch unit 3 S7 preferably has the following features: small size, the packaged size is, for example, 2 mm x 3 mm x 1 mm; low power consumption, less than 10 microamperes, and a switch point of more than ten gauss. Therefore, the liquid level sensor of the present invention can have a small volume, a wide range of use, a long service life, and high sensitivity. Further, by setting the position of the tunnel magnetoresistive switch in the non-magnetic duct 1 as needed, a liquid level sensor having a high resolution can be designed.
  • the number of tunnel magnetoresistive switches in the switching unit of the liquid level sensor may be,
  • Ns 2 N - m (1)
  • m is the number of invalid inputs on the encoder
  • m is 0, 1 , 2 , ... , 2 N -2 N-1
  • N is a natural number, and its specific value can be determined according to the requirements of the user.
  • each tunnel magnetoresistive switch is disposed at equal intervals along the axial direction of the non-magnetic conduit 1,
  • the distance between each two switches can be based on the axial length L of the non-magnetic conduit 1 , the remaining space of the unmounted switch at the upper and lower ends of the non-magnetic conduit 1 D1 , D2 and the number of tunnel magnetoresistive switches Ns And length L' to determine.
  • the distance DS between each two tunnel magnetoresistive switches is:
  • the resolution of the liquid level sensor is 7 mm.
  • the tunnel magnetoresistive switches are arranged along the axial direction of the non-magnetic duct 1 and are known along the axial position of the non-magnetic duct 1, and the tunnel magnet can be changed according to the position of the permanent magnet 6 fixed to the float 2 in response to the non-magnetic duct 1 outside.
  • the on/off signal of the resistance switch output determines the liquid level position in the liquid where the digital liquid level sensor is located.
  • the encoder generates a unique code for each position of the float to which the permanent magnet is fixed, based on the on-off signal from the tunnel magnetoresistive switch.
  • the encoder 15 is, for example, 8 lines -3 Line priority encoder.
  • the priority encoder allows input signals at multiple inputs at the same time.
  • the encoder encodes the highest priority among the several signals input simultaneously according to the priority order of the input signals. The signal with lower priority does not work. That is to say, among the signals output, only the highest priority is the active level.
  • 8 tunnel magnetoresistive switches S0-S7 and 8 line -3 line priority encoder 15 of 8 The input terminals are electrically connected respectively.
  • the 8-wire-3-wire priority encoder 15 The outputs then feed back the corresponding level information to the data bus 9 .
  • the data bus 9 has a width of at least 3 bits, which can be transmitted 8 Different binary digital signals. These eight binary digital signals reflect the corresponding position of the float, as shown in Table 1. In Table 1, the position of the float is numbered 0, 1, ..., 2 N -1 indicates that N is a natural number, and the number is linearly proportional to the height of the liquid surface.
  • the first column of Table 1 indicates the ratio of the liquid level to the full tank state
  • the second column indicates the position of the float, which is represented by the numerical number 0 ⁇ 7, where 0 Indicates the lowest liquid level position, not the empty tank status, and 7 indicates the highest liquid level position. The higher the number, the higher the position of the float in the container.
  • the third column is the output of 8 Combination of binary digital signals D2D1D0 and enable output NR The output value. According to the digital signal output in the third column, the corresponding position of the float in the second column can be obtained, so that the ratio of the liquid level in the first column to the state of the tank can be known, and then according to the liquid level at the full tank state, The height of the measured liquid level can be judged. For example, when When the output of the 8-wire -3 line priority encoder 15 is 110, it means that the ratio of the liquid level to the full tank state is 87.5%.
  • a tunnel magnetoresistance switch unit having a plurality of tunnel magnetoresistance switches For example, to use the tunnel magnetoresistive switch unit 3 In the case where the number of switches is more than 8 but not more than 64, a single 8-wire -3 line priority encoder 15 cannot meet the requirements. In this case, a 16-wire -4 line priority encoder can be used, 32 Line -5 line priority encoder, or 64 line -6 line priority encoder, multiple 8-line -3 line priority encoders can be used in accordance with the present invention 15 Such an encoder implements the above described finite encoder in the form of a cascade connection.
  • FIG. 4 is a diagram showing nine cascaded 8-wire-3 line priority encoders according to Embodiment 3 of the present invention. Schematic diagram. The number of tunnel magnetoresistance switches in the tunnel magnetoresistive switch unit 3 used in the figure is 64. These tunnel magnetoresistive switches S0-S63 and 8 8-wire -3 line priority encoders 16 , 17 , ... , 22, 23 The corresponding input is connected. The three 8-wire -3 line priority encoders 16-23 have three outputs respectively connected to the data bus 25 The corresponding interface is connected, and its output is represented by D0 ⁇ D2. The enable outputs NR of the eight 8-wire -3 line priority encoders 16-23 and the 8-wire -3 line priority encoders, respectively.
  • the tunnel magnetoresistive switch S0-S63 has a data bus 25 width of at least 6 bits.
  • the output of the 64 binary signals combined and the corresponding float position are shown in Table 2.
  • Table 2 The first column is the ratio of the liquid level to the full tank state, and the second column is the position of the float, which is represented by the numerical number 0 ⁇ 63, where 0 is the lowest liquid level position, not the empty groove state, 63 Indicates the highest liquid level position. The higher the number, the higher the position of the float in the container.
  • the third column is the output digital signal, and NR is the value that enables the output of the output, D0 ⁇ D5 Indicates the binary signal of the output. According to the combination of the binary signals of the six outputs, the position of the float can be known, so that the height of the liquid surface can be judged.
  • the number of switches in the tunnel magnetoresistive switch unit 3 to be used is more than 64.
  • a person skilled in the art can select a corresponding number of encoders to implement encoding of the output digital signal of the switching unit.
  • the encoder 4 can use a dedicated ASIC, FPGA, CPLD Or other programmable logic devices to achieve its width and cost savings.
  • the position of the float can be known, so that the height of the liquid level can be judged.
  • the tunnel magnetoresistive switches S0, S1, ... contain high-precision push-pull half-bridge TMR magnetic sensors and CMOS Integrated circuits, including TMR voltage generators, comparators, Schmitt triggers, and CMOS An output circuit that converts a varying magnetic field signal into a digital voltage signal output. It provides temperature compensation through an internal voltage regulator and allows for a wide operating voltage range.
  • the switch in the tunnel magnetoresistive switch unit 3 is a tunnel magnetoresistance single pole switch .
  • the magnetization direction of the permanent magnet outside the non-magnetic duct is parallel to the sensitive direction of the tunnel magnetoresistance single pole switch and parallel or perpendicular to the axial direction of the non-magnetic duct.
  • Tunnel magnetoresistance The output signal of a single pole switch is shown in Figure 5. Shown. In the figure, the magnetic field B- 26 ⁇ B+ 27 is the range of the magnetic field that the permanent magnet 6 can provide. Within this range, the single-pole switch can be opened or closed.
  • the unipolar switch when parallel to TMR When the magnetic field B in the sensitive direction of the magnetic sensor exceeds the operating point threshold B OP , the unipolar switch is turned off and the output is low. When the magnetic field B parallel to the sensitive direction of the TMR magnetic sensor is below the release point threshold B RP When the unipolar switch is closed, the output is high. Magnetic field operating point threshold B OP and release point threshold B RP is in the same direction of the magnetic field, and the release point threshold B RP can be 0 Gauss, the difference between them is the sensor's hysteresis B H .
  • the switch in the tunnel magnetoresistive switch unit 3 is a tunnel magnetoresistive bipolar switch.
  • the magnetization of the permanent magnet outside the non-magnetic conduit is parallel to the sensitive direction of the tunneling magnetoresistive bipolar switch and perpendicular to the axial direction of the non-magnetic conduit.
  • Tunnel magnetoresistance The output signal of the bipolar switch is shown in Figure 6. Shown. In the figure, the magnetic field B- 28 ⁇ B+ 29 is the range of the magnetic field that the permanent magnet 6 can provide. Within this range, the bipolar switch can be opened or closed. Magnetic field parallel to the sensitive direction of the TMR magnetic sensor When B exceeds the operating point threshold B OP, the bipolar switch is turned off and the output is low.
  • Magnetic field operating point threshold B OP and release point threshold B RP is in the opposite direction of the magnetic field, and their value cannot be 0 Gauss, the difference between them is the sensor's hysteresis B H .
  • the switch in the tunnel magnetoresistive switch unit 3 is a tunnel magnetoresistance all-pole switch. Magnetization direction of permanent magnets outside non-magnetic ducts Tunnel Magnetoresistance The sensitive direction of the single pole switch is parallel and parallel or perpendicular to the axial direction of the non-magnetic conduit. Tunnel Magnetoresistance The output signal of the all-pole switch is shown in Figure 7. In the picture, B-30 ⁇ B+ 31 The range of the magnetic field that the permanent magnet 6 can provide, within which the all-pole switch can be opened or closed. When the magnetic field B parallel to the sensitive direction of the TMR magnetic sensor exceeds the operating point threshold
  • Magnetic field operating point threshold B OPS and release point threshold The difference between B RPS is the sensor's hysteresis B HS , magnetic field operating point threshold B OPN The difference between the release point threshold and the R RPN is the sensor's hysteresis B HN , the release point threshold B RPS and the release point threshold B RPN can be 0 Gauss.

Abstract

一种数字液位传感器（100，200），包括非磁性导管（1），位于所述非磁性导管（1）外并可沿所述非磁性导管（1）轴向移动的浮子（2），和固定于所述浮子（2）的永磁体（6）。该非磁性导管（1）中进一步包括开关单元（3）和编码单元（4）。开关单元（3）包括至少一个在所述永磁体（6）产生的磁场作用下闭合或断开的隧道磁电阻开关（s0-s7），编码单元（4）包括至少一个编码器（15），其输入端分别接收来自所述隧道磁电阻开关（s0-s7）的通断信号并输出表征所述浮子（2）位置的数字信号。该数字液位传感器体积小、成本低、功耗低、可靠性高、灵敏度高、分辨率高、使用寿命长、抗干扰能力强，并能实现数字信号直接输出。

Description

数字液位传感器
技术领域
本发明涉及一种用于测量液位的传感器，尤其涉及一种利用高精度隧道磁电阻（ TMR ）开关和编码器实现数字信号输出的数字液位传感器。
背景技术
液位传感器广泛应用于石油、化工、电力、环保等领域， 对各种开口或有压容器内的液位或相界面进行连续测量，也可应用于液面或相界面的报警和控制 。目前，应用较多的是干簧管液位传感器和霍尔式液位传感器。干簧管液位传感器结构简单、价格低廉，可应用于限位、计数等，其工作原理是磁性浮子随液位高度变化而上下移动，所产生的磁场变化使磁簧开关产生动作。这类传感器的一种结构是当磁性浮子浮动到某个干簧管高度处时，该干簧管里的磁簧开关因受到外部磁场的作用而闭合，便形成了完整的闭合电路。当磁性浮子远离此干簧管时，即移除磁场，磁簧片由于自身的弹性而分开，使电路断开。这样根据所形成电路上的电阻大小，系统里的变送器产生相应大小的电流信号。通过检测所产生的电流信号，可以判断被测液位的高度。但干簧管液位传感器经常会发生个别开关该断开未断开的故障，造成虚假液位，并且由于干簧管的尺寸较大，限制了传感器的分辨频率。当传感器受到冲击、磨损和振动等影响时，传感器内部的玻璃壳会因此而容易破裂，这也致使传感器不易安装和焊接。进一步，当存在电感和电容负载时，传感器的使用寿命会受到影响。此外，干簧管液位传感器的输出是模拟信号，抗干扰能力差，因而需要进一步的数字处理电路将模拟信号处理为数字信号。
霍尔式液位传感器工作原理与干簧管液位传感器相同，只是用开关式霍尔片代替了干簧管，其尺寸比干簧管的尺寸要小，也易于安装和焊接，并且其输出信号是经过 A/D 转换后的数字信号，抗干扰能力较强。但因为霍尔元件功耗较高，为毫安级，开关点也达到几十高斯，这种液位传感器需要经常维修和更换，增加了使用成本。
发明内容
本发明的目的在于克服现有技术存在的以上问题，提供一种新颖的、先进的、可靠的数字液位传感器。本发明利用隧道磁电阻开关在外部磁场的作用下产生动作，将其所在状态以高、低电平的形式传达给与其连接的编码器，再通过编码器将数字信号提供给数据总线，从而实现准确快速的判断所测液位的高度。
为实现上述技术目的，达到上述技术效果，本发明通过以下技术方案实现：
一种数字液位传感器，其将测量的液位转换为数字信号输出，该数字液位传感器包括以下几个部分：
数据总线；
电源端子；
接地端子；
固定并且放置在液体里的非磁性导管；
漂浮在所述液体中的浮子，所述浮子邻近所述非磁性导管放置, 随着液位的变化，所述浮子沿所述非磁性导管的轴向上下移动；
固定于所述浮子的永磁体；
至少一个隧道磁电阻开关，所述隧道磁电阻开关在所述永磁体产生的磁场作用下可闭合或者断开，所述永磁体产生具有足够幅度和方向的磁场以使与该永磁体处于相同水平的一个或多个隧道磁电阻开关闭合或断开；
至少一个编码器，所述编码器为所述浮子的每一个位置产生唯一的编码；
一个或者多个密封在所述非磁性导管中的印刷电路板，所述隧道磁电阻开关、所述编码器、所述数据总线、所述电源端子和所述接地端子安装在所述印刷电路板上且相互电联。
优选地，所述非磁性导管的轴向长度为10~12000 mm，外直径为12~40 mm。
优选地，所述浮子的宽度为10~200 mm，高度为10~200 mm 。
优选地，所述永磁体的磁化方向与所述非磁性导管的轴向平行，所述隧道磁电阻开关为 隧道磁电阻 全极开关或 隧道磁电阻 单极开关，并且其敏感方向与所述非磁性导管的轴向平行。
优选地，所述永磁体的磁化方向与所述非磁性导管的轴向垂直，所述隧道磁电阻开关为 隧道磁电阻 全极开关、 隧道磁电阻 双极开关或 隧道磁电阻 单极开关并且其敏感方向与所述非磁性导管的轴向垂直。
优选地，所述非磁性导管与所述浮子同轴放置，所述浮子的内径大于所述非磁性导管的外径。
优选地，所述隧道磁电阻开关等间距放置在所述印刷电路板上。
优选地，所述编码器为优先编码器。
优选地，每一个所述编码器有 2 N 个不同的输入端，有N个不同的输出端，N为自然数。
优选地，所述浮子的位置用数字0,1, …，2 N -1来表示，N为自然数，所述数字与所述液面的高度呈线性比例关系。
优选地，所述编码器为专用 ASIC 、 FPGA 、 CPLD 或其他可编程逻辑器件，来最小化所述印刷电路板上部件的数量。
优选地，对于 2 N 个所述隧道磁电阻开关，所述数据总线的宽度至少为 N 位，N为自然数。
优选地，所述隧道磁电阻开关分别与所述编码器的相应的输入 接口 电连接。
优选地，所述编码器的输出接口与所述数据总线上的相应接口电连接。
优选地，所述印刷电路板是柔性印刷线路板。
优选地，所述编码器和所述隧道磁电阻开关放置在由柔性印刷线路板互连的多个小型刚性印刷电路板上。 本文此处及其它各处所提及的小型刚性印刷电路板，是相对大型刚性印刷电路板定义的，其尺寸可以很小，只要保证能 容纳隧道磁电阻开关、编码器、数据总线、电源端子和接地端子 即可。
一种数字液位传感器，包括：
非磁性导管，和
位于所述非磁性导管外并可沿所述非磁性导管轴向移动的浮子，
固定于所述浮子的永磁体，
所述非磁性导管中进一步包括：
开关单元，包括至少一个在所述永磁体产生的磁场作用下闭合或断开的隧道磁电阻开关，
编码单元，包括至少一个编码器，所述编码单元的输入端分别接收来自所述隧道磁电阻开关的通断信号并输出表征所述浮子位置的数字信号。
优选地，该液位传感器包括 2 N 个隧道磁电阻开关，各隧道磁电阻开关沿所述非磁性导管的轴向排列设置且沿非磁性导管轴向的位置已知。
与现有技术相比，本发明采用隧道磁电阻开关对浮子的位置进行检测，并采用优先编码器对来自隧道磁电阻开关的开关信号进行编码。本发明具有以下有益效果：体积小、成本低、功耗低、可靠性高、灵敏度高、分辨率高、使用寿命长、抗干扰能力强，并能实现数字信号直接输出。
上述说明仅是本发明技术方案的概述，为了能够更清楚了解本发明的技术手段，并可依照说明书的内容予以实施，以下将对本发明的较佳实施例并结合附图进行详细说明。
附图说明
此处所说明的附图用来提供对本发明的进一步理解，构成本申请的一部分，本发明的示意性实施例及其说明用于解释本发明，并不构成对本发明的不当限定。在附图中：
图 1 为根据本发明实施例1的液位传感器结构示意图。
图 2 为根据本发明实施例1的液位传感器另一种结构示意图。
图 3 为根据本发明实施例2的隧道磁电阻开关和优先编码器的连接示意图。
图 4 根据本发明实施例3的隧道磁电阻开关和优先编码器的连接示意图。
图 5 为隧道磁电阻单极开关信号示意图。
图 6 为隧道磁电阻双极开关信号示意图。
图 7 为隧道磁电阻全极开关信号示意图 。
具体实施方式
下面将参考附图并结合实施例，来详细说明本发明。
实施例1
图 1 和图2 分别示出根据本发明实施例1的液位传感器100，200的结构示意图，图中示意性显示出一种使用隧道磁电阻开关单元 3 和编码器 4 实现数字信号输出的数字液位传感器。该传感器包括一根可相对于待测容器固定的非磁性导管 1 ，一个可在液体 11 中漂浮，并沿 非磁性导管 1 外表面随液面变化而上下滑动的浮子 2 。优选地， 非磁性导管 1 的横截面外轮廓呈圆形， 非磁性导管 1 和浮子 2 的中心轴相同。非磁性导管 1 里装有印刷电路板 5 ，优选是柔性印刷线路板。印刷电路板 5 上 安装有隧道磁电阻开关单元 3 、编码器 4 、数据总线 9 以及电源端子 7 和接地端子 8 。 编码器和磁电阻开关也可安装在多个小型刚性印刷电路板上，相互之间用柔性印刷线路板或者电布线连接。 隧道磁电阻开关单元 3 包括多个隧道磁电阻开关，各隧道磁电阻开关在非磁性导管中具有确定的位置。 在浮子 2 里有一个固定的永磁体 6 ， 该永磁体 6 可产生使隧道磁电阻开关单元 3 中 与其大致在同一液面高度处 的隧道磁电阻开关 产生动作所需要的 足够大幅度和方向的 磁场，永磁体 6 内部的 磁化方向 12 可以与非磁性导管 1 的轴向 13 平行，如图1所示，也可以与非磁性导管 1 的轴向 13 垂直，如图 2 所示 。隧道磁电阻开关单元 3 的各个输出端 与编码器 4 的相应输入接口依次电连接，编码器 4 的输出接口与数据总线 9 的相应接口依次电连接，其使能输出端 14 与数据总线或下一级的编码器的相应输入接口电连接。当液位传感器置于液体11中时，浮子 2 漂浮在液体 11 的液面上，随液面位置的变化而 沿 非磁性导管 1 外表面上下移动，浮子 2 里的永磁体 6 在非磁性导管 1 周围产生了稳定磁场。隧道磁电阻开关单元 3 中相应位置的隧道磁电阻开关 在永磁体 6 产生的磁场作用下产生 闭合或者断开 动作，将其所在状态以高或低电平的形式输出给与其连接的编码器 4 。 每个编码器有 2 N 个输入端 和N个输出端，N是自然数。 编码器 4 对来自开关单元3的各个输入进行编码将数字信号输出至 数据总线，根据所输出的数字信号便能确定出液面的高度。 对于 2 N 个隧道磁电阻开关，数据总线的宽度至少为 N 位。
根据液位传感器的使用环境和使用条件，非磁性导管 1 优选的具有以下特征，例如 12~ 40 mm 的外直径， 10~12000 mm 的轴向长度，可以是直管，也可以是弯管，其制成材料可以为耐腐蚀的适用的金属、合金或结实耐用的工程塑料。
优选地，浮子2与非磁性导管1同轴设置 ，浮子2的内径大于非磁性导管1的外径 。浮子2的 宽度优选为10~200 mm，高度优选为10~200 mm。浮子2上 固定有永磁体6，带动永磁体6一起随液位的高低变化沿非磁性导管1的轴向上下移动。永磁体6可以固定在浮子2内，也可以固定在浮子2外。
隧道磁电阻开关单元 3 中的每一个隧道磁电阻开关S0，S1， … , S7优选的具有以下特征：体积小，经过封装后的尺寸例如为 2mm x 3 mm x 1mm ； 功耗低 ，低于 10 微安，开关点十几高斯。 因而本发明的液位传感器可以具有较小的体积，使用范围广泛；使用寿命长；灵敏度高。进一步通过根据需要设置隧道磁电阻开关在非磁性导管1中的位置，可以设计具有高分辨率的液位传感器。
具体地，液位传感器的开关单元中隧道磁电阻开关的数量可以是，
Ns = 2 N - m (1)
式中 m 表示编码器上无效的输入端的数量，m取值为 0 ， 1 ， 2 ， … ， 2 N -2 N-1 ， N 为自然数，其具体数值可根据用户的要求来确定。各 隧道磁电阻开关S0，S1， … , S7 沿所述非磁性导管1的轴向排列设置，各隧道磁电阻开关沿非磁性导管1的轴向位置已知 。优选的，各隧道磁电阻开关 沿所述非磁性导管1的轴向等间距设置， 每两个开关之间的距离可根据非磁性导管 1 的轴向长度 L 、非磁性导管 1 上下两端的未安装开关的剩余空间 D1 、 D2 以及 隧道磁电阻开关的数量 Ns 和长度 L' 来确定。例如，对于长度为 1000mm 、上下两端的剩余空间均为 50mm 的非磁性导管 1 以及具有 100 个长度为 2mm 的隧道磁电阻开关的开关单元 3 ，则每两个隧道磁电阻开关之间的距离DS为:
DS= ( L-D1-D2-Ns*L' ) /Ns= ( 1000-2*50-100*2 ) /100=7mm (2)
由此可知，该液位传感器的分辨率为7mm 。
本领域技术人员可以理解，只要 隧道磁电阻开关沿非磁性导管1的轴向排列设置且沿非磁性导管1轴向的位置已知，则可根据响应于非磁性导管1外固定于浮子2的永磁体6的位置改变隧道磁电阻开关输出的通断信号，确定数字液位传感器所处液体里的液位位置。
实施例2
图 3 为实施例1中隧道磁电阻开关和优先编码器的连接示意图。 本发明中编码器根据来自隧道磁电阻开关的通断信号，为固定有永磁体的浮子的每一个位置产生唯一的编码。 在该实施例中，编码器15例如是 8 线 -3 线优先编码器。优先编码器允许同时在多个输入端有输入信号，编码器按输入信号排定的优先顺序，只对同时输入的几个信号中优先权最高的一个进行编码，优先级低的信号不起作用，也就是说在所输出的信号中，只有优先级最高的为有效电平。使用此类型的编码器，即使有几个隧道磁电阻开关在外部磁场的作用下同时产生动作，优先编码器也只会对优先级最高的进行编码，输出一个有效电平，从而能准确快速的判断液面位置，避免了浮子附近的开关的错误动作造成虚假液位的情形。例如，如图3所示，对于隧道磁电阻开关单元 3 中开关的数量 Ns 不多于 8 个的情形，例如可以只用一个 8 线 -3 线优先编码器 15 。图 3 显示了具有 8 个隧道磁电阻开关 S0-S7 的开关单元和一个 8 线 -3 线优先编码器 15 的连接示意图。图中， 8 个隧道磁电阻开关 S0-S7 与 8 线 -3 线优先编码器 15 的 8 个输入端分别电连接，当隧道磁电阻开关 S0-S7 中的一个或者几个在外部磁场的作用下产生动作时， 8 线 -3 线优先编码器 15 的 3 个输出端便将相应的电平信息反馈给数据总线 9 。对于 8 （ =2 3 ）个隧道磁电阻开关 S0-S7 ，数据总线 9 的宽度至少为 3 位，其可以传送出 8 种不同的二进制数字信号。这 8 种二进制数字信号便反映了浮子的相应位置，如表 1 所示。 表1中，浮子的位置用数字0,1, …，2 N -1来表示，N为自然数，所述数字与所述液面的高度呈线性比例关系。
表 1 浮子位置、所对应的液面与输出的数字信号之间的关系
液面占满槽状态的比率 (%) 浮子位置 输出的数字信号
NR D2 D1 D0
0 空 0 0 0 0
12.5 0 1 0 0 0
25 1 1 0 0 1
37.5 2 1 0 1 0
50 3 1 0 1 1
62.5 4 1 1 0 0
75 5 1 1 0 1
87.5 6 1 1 1 0
100 7 1 1 1 1
表 1 的第一栏表示液面占满槽状态的比率，第二栏表示浮子的位置，用数字编号 0~7 表示，其中 0 表示最低的液面位置，不为空槽状态， 7 表示最高的液面位置。编号越大，表示浮子在容器中的位置越高。第三栏是输出的 8 种二进制数字信号D2D1D0的组合以及使能输出端 NR 的输出值。根据第三栏的数字信号输出，便可以得到第二栏中浮子的相应位置，从而可以得知第一栏中液面占满槽状态的比率，再根据满槽状态时的液面高度，便可以判断出所测液面的高度。例如，当 8 线 -3 线优先编码器 15 的输出为110时，表示此时液面占满槽状态的比率为87.5%。
实施例3
当需要测量的液位的容器很深或对液位测量精度要求较高时，需要选择具有较多隧道磁电阻开关的隧道磁电阻开关单元。例如，对于要使用隧道磁电阻开关单元 3 中开关的数量多于 8 个但不多于 64 个的情形，单个的 8 线 -3 线优先编码器 15 便不能满足要求，这时可以使用 16 线 -4 线优先编码器、 32 线 -5 线优先编码器、或者 64 线 -6 线优先编码器，根据本发明可以采用多个像 8 线 -3 线优先编码器 15 这样的编码器以级联连接的形式来实现上述有限编码器。 图 4 所示为根据本发明实施例3的 9 个级联连接的 8 线 -3 线优先编码器 16-24 的示意图。图中所用隧道磁电阻开关单元 3 中隧道磁电阻开关的数量为 64 个。这些隧道磁电阻开关 S0-S63 分别与 8 个 8 线 -3 线优先编码器 16 ，17， … ，22， 23 相应的输入端连接，这 8 个 8 线 -3 线优先编码器 16-23 的三个输出端分别与数据总线 25 的相应接口连接，其输出用 D0~D2 表示。这 8 个 8 线 -3 线优先编码器 16-23 的使能输出端 NR 分别与 8 线 -3 线优先编码器 24 相应的输入端电连接， 8 线 -3 线优先编码器 24 的三个输出端与数据总线 25 的相应接口连接，输出结果用 D3~D5 表示。对于 64 （ =2 6 ）个隧道磁电阻开关 S0-S63 ，数据总线 25 的宽度至少为 6 位。输出的 64 种二进制信号组合结果以及相应的浮子位置如表 2 所示。表 2 中，第一栏为液面占满槽状态的比率，第二栏为浮子的位置，用数字编号 0~63 表示，其中 0 表示最低的液面位置，不为空槽状态， 63 表示最高的液面位置。编号越大，表示浮子在容器中的位置越高。 第三栏为输出的数字信号， NR 表示使能输出端输出的数值， D0~D5 表示输出的二进制信号。根据这六种输出的二进制信号结果组合，便可得知浮子所在位置，从而可以判断出液面的高度。
表 2 浮子位置、所对应的液面与输出的数字信号之间的关系
液面占满槽状态的比率 (%) 浮子 位置 MS LS 液面占满槽状态的比率 (%) 浮子位置 MS LS
NR D5 D4 D3 D2 D1 D0 NR D5 D4 D3 D2 D1 D0
0 空 0 0 0 0 0 0 0
1.56 0 1 0 0 0 0 0 0 51.56 32 1 1 0 0 0 0 0
3.12 1 1 0 0 0 0 0 1 53.13 33 1 1 0 0 0 0 1
4.68 2 1 0 0 0 0 1 0 54.68 34 1 1 0 0 0 1 0
6.25 3 1 0 0 0 0 1 1 56.25 35 1 1 0 0 0 1 1
7.81 4 1 0 0 0 1 0 0 57.81 36 1 1 0 0 1 0 0
9.38 5 1 0 0 0 1 0 1 59.38 37 1 1 0 0 1 0 1
10.94 6 1 0 0 0 1 1 0 60.94 38 1 1 0 0 1 1 0
12.5 7 1 0 0 0 1 1 1 62.5 39 1 1 0 0 1 1 1
14.06 8 1 0 0 1 0 0 0 64.06 40 1 1 0 1 0 0 0
15.63 9 1 0 0 1 0 0 1 65.63 41 1 1 0 1 0 0 1
17.19 10 1 0 0 1 0 1 0 67.19 42 1 1 0 1 0 1 0
18.75 11 1 0 0 1 0 1 1 68.75 43 1 1 0 1 0 1 1
20.31 12 1 0 0 1 1 0 0 70.31 44 1 1 0 1 1 0 0
21.88 13 1 0 0 1 1 0 1 71.88 45 1 1 0 1 1 0 1
23.44 14 1 0 0 1 1 1 0 73.44 46 1 1 0 1 1 1 0
25 15 1 0 0 1 1 1 1 75 47 1 1 0 1 1 1 1
26.56 16 1 0 1 0 0 0 0 76.56 48 1 1 1 0 0 0 0
28.13 17 1 0 1 0 0 0 1 78.13 49 1 1 1 0 0 0 1
29.69 18 1 0 1 0 0 1 0 79.69 50 1 1 1 0 0 1 0
31.25 19 1 0 1 0 0 1 1 81.25 51 1 1 1 0 0 1 1
32.81 20 1 0 1 0 1 0 0 82.81 52 1 1 1 0 1 0 0
34.38 21 1 0 1 0 1 0 1 84.38 53 1 1 1 0 1 0 1
35.94 22 1 0 1 0 1 1 0 85.94 54 1 1 1 0 1 1 0
37.5 23 1 0 1 0 1 1 1 87.5 55 1 1 1 0 1 1 1
39.06 24 1 0 1 1 0 0 0 89.06 56 1 1 1 1 0 0 0
40.63 25 1 0 1 1 0 0 1 90.63 57 1 1 1 1 0 0 1
42.19 26 1 0 1 1 0 1 0 92.19 58 1 1 1 1 0 1 0
43.75 27 1 0 1 1 0 1 1 93.75 59 1 1 1 1 0 1 1
45.31 28 1 0 1 1 1 0 0 95.31 60 1 1 1 1 1 0 0
46.87 29 1 0 1 1 1 0 1 96.88 61 1 1 1 1 1 0 1
48.44 30 1 0 1 1 1 1 0 98.44 62 1 1 1 1 1 1 0
50 31 1 0 1 1 1 1 1 100 63 1 1 1 1 1 1 1
本领域技术人员可以理解，对于要使用的隧道磁电阻开关单元 3 中开关的数量多于 64 个的情形，本领域技术人员可以选择相应数量的编码器实现对开关单元输出数字信号的编码。当然， 编码器 4 可以用专用的 ASIC 、 FPGA 、 CPLD 或其他可编程逻辑器件来实现以扩大其宽度以及节约成本 。
在实施例2和实施例3中，根据这种输出的二进制信号结果组合，便可得知浮子所在位置，从而可以判断出液面的高度。
实施例4
隧道磁电阻开关S0，S1， … ，的芯片内含有高精度推挽式半桥 TMR 磁传感器和 CMOS 集成电路，包括 TMR 电压发生器、比较器、施密特触发器和 CMOS 输出电路，能将变化的磁场信号转化为数字电压信号输出。其通过内部电压稳压器来提供温度补偿，并允许宽的工作电压范围。
本发明的一种实施例，隧道磁电阻开关单元 3 中开关的为隧道磁电阻单极开关 。在非磁性导管外的永磁体的磁化方向与 隧道磁电阻 单极开关的敏感方向平行，与非磁性导管的轴向平行或者垂直。 隧道磁电阻 单极开关的输出信号示意图如图 5 所示。图中，磁场 B- 26~B+ 27 为永磁体 6 所能提供的磁场大小范围，在此范围内，单极开关能断开或者闭合。例如，当平行于 TMR 磁传感器敏感方向的磁场 B 超过工作点门限 B OP 时，单极开关便断开，输出低电平。当平行于 TMR 磁传感器敏感方向的磁场 B 低于释放点门限 B RP 时，单极开关便闭合，输出高电平。磁场工作点门限 B OP 和释放点门限 B RP 位于同一方向的磁场中，并且释放点门限 B RP 可以为 0 高斯，它们之间的差值就是传感器的回差 B H 。
实施例5
在该实施例中，隧道磁电阻开关单元 3 中的开关为隧道磁电阻双极开关 。在非磁性导管外的永磁体的磁化方向与该 隧道磁电阻 双极开关的敏感方向平行，与非磁性导管的轴向垂直。 隧道磁电阻 双极开关的输出信号示意图如图 6 所示。图中， 磁场 B- 28~B+ 29 为永磁体 6 所能提供的磁场大小范围，在此范围内，双极开关能断开或者闭合。当平行于 TMR 磁传感器敏感方向的磁场 B 超过工作点门限 B OP 时，该双极开关便断开，输出低电平。当平行于 TMR 磁传感器敏感方向的磁场 B 低于释放点门限 B RP 时，该双极开关便闭合，输出高电平。磁场工作点门限 B OP 和释放点门限 B RP 位于相反方向的磁场中，并且它们的取值不能为 0 高斯，它们之间的差值就是传感器的回差 B H 。
实施例6
在实施例中，隧道磁电阻开关单元 3 中的开关为隧道磁电阻全极开关 。在非磁性导管外的永磁体的磁化方向与 隧道磁电阻 单极开关的敏感方向平行，与非磁性导管的轴向平行或者垂直。 隧道磁电阻 全极开关的输出信号示意图如图 7 所示。图中， B- 30~B+ 31 为永磁体 6 所能提供的磁场大小范围，在此范围内，全极开关能断开或者闭合。当平行于 TMR 磁传感器敏感方向的磁场 B 超过工作点门限 |B OPS | （ |B OPN | ）时，全极开关便断开，输出低电平。当平行于 TMR 磁传感器敏感方向的磁场 B 低于释放点门限 |B RPS | （ |B RPN | ）时，全极开关便闭合，输出高电平。磁场工作点门限 B OPS 和释放点门限 B RPS 之间的差值就是传感器的回差 B HS ，磁场工作点门限 B OPN 和释放点门限 B RPN 之间的差值就是传感器的回差 B HN ，释放点门限 B RPS 和释放点门限 B RPN 可以为 0 高斯。
以上所述仅为本发明的优选实施例而已，并不用于限制本发明，对于本领域的技术人员来说，本发明可以有各种更改和变化。凡在本发明的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内 。

Claims (17)

1．一种数字液位传感器，其将测量的液位转换为数字信号输出，其特征在于，该数字液位传感器包括以下几个部分：
数据总线；
电源端子；
接地端子；
固定并且放置在液体里的非磁性导管；
漂浮在所述液体中的浮子，所述浮子邻近所述非磁性导管放置, 随着液位的变化，所述浮子沿所述非磁性导管的轴向上下移动；
固定于所述浮子的永磁体；
至少一个隧道磁电阻开关，所述隧道磁电阻开关在所述永磁体产生的磁场作用下可闭合或者断开，所述永磁体产生具有足够大幅度和方向的磁场以使与该永磁体处于相同水平的一个或多个隧道磁电阻开关闭合或断开；
至少一个编码器，所述编码器为所述浮子的每一个位置产生唯一的编码；
一个或者多个密封在所述非磁性导管中的印刷电路板，所述隧道磁电阻开关、所述编码器、所述数据总线、所述电源端子和所述接地端子安装在所述印刷电路板上且相互电联。
2．根据权利要求1所述的数字液位传感器，其特征在于，所述非磁性导管的轴向长度为10~12000 mm，外直径为12~40 mm。
3. 根据权利要求1所述的数字液位传感器，其特征在于，所述浮子的宽度为10~200 mm，高度为10~200 mm 。
4. 根据权利要求1所述的数字液位传感器，其特征在于，所述永磁体的磁化方向与所述非磁性导管的轴向平行，所述隧道磁电阻开关为 隧道磁电阻 全极开关或 隧道磁电阻 单极开关，并且其敏感方向与所述非磁性导管的轴向平行。
5．根据权利要求1所述的数字液位传感器，其特征在于，所述永磁体的磁化方向与所述非磁性导管的轴向垂直，所述隧道磁电阻开关为 隧道磁电阻 全极开关、 隧道磁电阻 双极开关或 隧道磁电阻 单极开关，并且其敏感方向与所述非磁性导管的轴向垂直。
6．根据权利要求1所述的数字液位传感器，其特征在于，所述非磁性导管与所述浮子同轴放置，所述浮子的内径大于所述非磁性导管的外径。
7．根据权利要求1所述的数字液位传感器，其特征在于，所述隧道磁电阻开关等间距放置在所述印刷电路板上。
8．根据权利要求1所述的数字液位传感器，其特征在于，所述编码器为优先编码器。
9．根据权利要求8所述的数字液位传感器，其特征在于，每一个所述编码器有 2 N 个不同的输入端，有N个不同的输出端，N为自然数。
10．根据权利要求8所述的数字液位传感器，其特征在于，所述浮子的位置用数字0,1, …，2 N -1来表示，N为自然数，所述数字与所述液面的高度呈线性比例关系。
11．根据权利要求1所述的数字液位传感器，其特征在于，所述编码器为专用 ASIC 、 FPGA 、 CPLD 或其他可编程逻辑器件，来最小化所述印刷电路板上部件的数量。
12．根据权利要求1所述的数字液位传感器，其特征在于，对于 2 N 个所述隧道磁电阻开关，所述数据总线的宽度至少为 N 位，N为自然数。
13．根据权利要求1所述的数字液位传感器，其特征在于，所述隧道磁电阻开关分别与所述编码器的相应的输入 接口 电连接。
14．根据权利要求1所述的数字液位传感器，其特征在于，所述编码器的输出接口与所述数据总线上的相应接口电连接。
15．根据权利要求1所述的数字液位传感器，其特征在于，所述印刷电路板是柔性印刷线路板。
16．根据权利要求1所述的数字液位传感器，其特征在于，所述编码器和所述隧道磁电阻开关放置在由柔性印刷线路板互连的多个小型刚性印刷电路板上。
17．一种数字液位传感器，包括：
非磁性导管，和
位于所述非磁性导管外并可沿所述非磁性导管轴向移动的浮子，
其特征在于，
固定于所述浮子的永磁体，
所述非磁性导管中进一步包括：
开关单元，包括至少一个在所述永磁体产生的磁场作用下闭合或断开的隧道磁电阻开关，
编码单元，包括至少一个编码器，所述编码单元的输入端分别接收来自所述隧道磁电阻开关的通断信号并输出表征所述浮子位置的数字信号。
18．根据权利要求17所述的数字液位传感器，其特征在于，该液位传感器包括 2 N 个隧道磁电阻开关，各隧道磁电阻开关沿所述非磁性导管的轴向排列设置且沿非磁性导管轴向的位置已知。
PCT/CN2014/071351 2013-01-25 2014-01-24 数字液位传感器 WO2014114259A1 (zh)

Priority Applications (3)

Application Number Priority Date Filing Date Title
EP14742929.4A EP2950060B1 (en) 2013-01-25 2014-01-24 Digital liquid-level sensor
US14/763,431 US11035716B2 (en) 2013-01-25 2014-01-24 Digital liquid-level sensor having at least one tunneling magnetoresistance switch
JP2015554042A JP6215961B2 (ja) 2013-01-25 2014-01-24 デジタル液体レベルセンサ

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CN201310029455.1 2013-01-25
CN201310029455.1A CN103968918B (zh) 2013-01-25 2013-01-25 数字液位传感器

Publications (1)

Publication Number Publication Date
WO2014114259A1 true WO2014114259A1 (zh) 2014-07-31

Family

ID=51226944

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2014/071351 WO2014114259A1 (zh) 2013-01-25 2014-01-24 数字液位传感器

Country Status (5)

Country Link
US (1) US11035716B2 (zh)
EP (1) EP2950060B1 (zh)
JP (1) JP6215961B2 (zh)
CN (1) CN103968918B (zh)
WO (1) WO2014114259A1 (zh)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPWO2016163171A1 (ja) * 2015-04-06 2018-01-11 株式会社村田製作所 液面検出装置
WO2020177595A1 (zh) 2019-03-04 2020-09-10 江苏多维科技有限公司 一种基于磁阻传感器交叉点阵列的数字液位传感器
US11035716B2 (en) 2013-01-25 2021-06-15 MultiDimension Technology Co., Ltd. Digital liquid-level sensor having at least one tunneling magnetoresistance switch
EP3304010B1 (fr) * 2015-05-29 2021-12-15 Safran Aircraft Engines Capteur de niveau d'huile

Families Citing this family (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9890029B2 (en) * 2011-12-09 2018-02-13 Electrolux Home Products, Inc. Refrigerator with automatic liquid dispenser
BE1024049B1 (nl) * 2015-11-11 2017-11-08 Melexis Technologies Nv Magnetische sensor
CN105865581A (zh) * 2016-05-30 2016-08-17 国家电网公司 液位计
CN106197619A (zh) * 2016-07-12 2016-12-07 苏州依斯倍环保装备科技有限公司 液位监测装置
CN106092273B (zh) * 2016-08-11 2022-08-02 东莞正扬电子机械有限公司 液位检测方法及液位传感器
CN107782415B (zh) * 2016-08-30 2020-11-10 株式会社村田制作所 液面检测装置
WO2018085987A1 (en) * 2016-11-08 2018-05-17 Hamlin Electronics (Suzhou) Co. Ltd. Unipolar resistive ladder sensor
US10436626B2 (en) * 2017-07-27 2019-10-08 Pratt & Whitney Canada Corp. Multi-channel fluid level sensor
CN108195442A (zh) * 2018-01-24 2018-06-22 北京麦格智能科技有限公司 Tmr液位传感器
CN109060079A (zh) * 2018-10-23 2018-12-21 潍坊通达仪表有限公司 基于双恒流源的液位传感器和变送器系统
CN112368552A (zh) 2018-11-30 2021-02-12 开利公司 磁性捕集抑制罐水平传感器
US11378436B2 (en) 2018-12-10 2022-07-05 Carrier Corporation Adjustable liquid level indicators
CN109545602B (zh) * 2018-12-18 2020-10-09 深圳市万普拉斯科技有限公司 多段式开关及电子设备
GB2581323A (en) 2018-12-31 2020-08-19 Essence Security International Esi Ltd Magnetic field sensor for an access point
US11366001B2 (en) * 2019-01-08 2022-06-21 Pratt & Whitney Canada Corp. Fluid level sensor, fluid reserviour, and methods for sensing a fluid level
US11402251B2 (en) * 2019-03-22 2022-08-02 Christopher J. Brown Fuel tank assembly
CN110440872B (zh) * 2019-08-23 2021-01-26 江苏多维科技有限公司 一种磁感应料位计
US20210123788A1 (en) * 2019-10-29 2021-04-29 Littelfuse, Inc. Omnipolar magnetic switch with axially magnetized magnet assembly for improved precision
EP4040118A1 (en) * 2021-02-08 2022-08-10 Tetra Laval Holdings & Finance S.A. Level reader device, level reader system and package producing machine comprising the level reader system
CN112945074B (zh) * 2021-02-20 2022-09-30 杭州鲲骏海洋工程技术有限公司 一种全海深非接触隧道磁电阻阵列位移传感器
CN113701615A (zh) * 2021-08-23 2021-11-26 上海米尔圣传感器有限公司 位置传感器及位置检测装置
RU208697U1 (ru) * 2021-10-04 2021-12-30 Общество с ограниченной ответственностью "Зарио" Датчик уровня жидкости
WO2023199161A1 (en) * 2022-04-12 2023-10-19 G.D S.P.A. Apparatus for detecting the level of a liquid product in a packaging machine
US11780722B1 (en) * 2022-10-14 2023-10-10 Haier Us Appliance Solutions, Inc. Autofill pitcher overfill shutoff mechanism

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1580717A (zh) * 2004-05-16 2005-02-16 刘珉恺 一种密封管道编码式液位仪
CN102768057A (zh) * 2012-07-06 2012-11-07 广东美的制冷设备有限公司 一种水位开关及水位信号检测装置
CN202814504U (zh) * 2011-12-29 2013-03-20 武汉盛硕电子有限公司 基于磁阻效应的油位传感器
CN103105216A (zh) * 2013-01-29 2013-05-15 佛山市川东磁电股份有限公司 一种磁敏传感器及其制造工艺
CN203053525U (zh) * 2013-01-29 2013-07-10 佛山市川东磁电股份有限公司 一种mr磁阻磁敏传感器
CN203083663U (zh) * 2013-01-25 2013-07-24 江苏多维科技有限公司 数字液位传感器

Family Cites Families (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4361835A (en) * 1981-03-16 1982-11-30 Sprague Electric Company Hall-cell liquid level detector
US4409694A (en) * 1982-09-30 1983-10-18 John P. Barrett, Sr. Electronic control device for liquids
US5056049A (en) * 1989-10-23 1991-10-08 Neill Timothy P O Position Transmitter
US5636548A (en) * 1994-05-16 1997-06-10 Tesoro Alaska Petroleum Company Analog hall-effect liquid level detector and method
JPH0886684A (ja) * 1994-09-16 1996-04-02 Sanyo Electric Co Ltd レベルセンサー
CN2275232Y (zh) * 1995-09-05 1998-02-25 夏开华 无介质式测量传感器
EP0938649A4 (en) 1996-10-24 2002-05-29 Karl A Senghaas SENSOR FOR DETERMINING THE RELATIVE POSITION
CN2303279Y (zh) * 1997-07-24 1999-01-06 汪文良 磁浮跟随液位计
CN2392172Y (zh) * 1999-10-20 2000-08-16 陈亮 数字式电子测位计
US6633462B2 (en) * 2000-07-13 2003-10-14 Koninklijke Philips Electronics N.V. Magnetoresistive angle sensor having several sensing elements
US6546797B2 (en) * 2000-08-24 2003-04-15 Mlho, Inc. Absolute position measure with multi-beam optical encoding
US6690159B2 (en) * 2000-09-28 2004-02-10 Eldec Corporation Position indicating system
DE10308030B4 (de) 2003-02-24 2011-02-03 Meas Deutschland Gmbh Magnetoresistiver Sensor zur Bestimmung eines Winkels oder einer Position
US7394244B2 (en) * 2003-10-22 2008-07-01 Parker-Hannifan Corporation Through-wall position sensor
US20060238281A1 (en) * 2005-04-22 2006-10-26 Steinberg Dan A Keyboard having magnet-actuated switches or sensors
DE102010025170B4 (de) 2010-06-25 2013-02-28 Meas Deutschland Gmbh Vorrichtung zum Erzeugen eines Sensorsignals und Verfahren zur Bestimmung der Position eines Gebers
CN102419425B (zh) * 2011-09-09 2013-12-04 兰州大学 一种磁电阻自动测量装置及其测量方法
CN202372135U (zh) * 2011-12-23 2012-08-08 基康仪器(北京)有限公司 磁体位移传感器
CN103968918B (zh) 2013-01-25 2018-11-09 江苏多维科技有限公司 数字液位传感器

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1580717A (zh) * 2004-05-16 2005-02-16 刘珉恺 一种密封管道编码式液位仪
CN202814504U (zh) * 2011-12-29 2013-03-20 武汉盛硕电子有限公司 基于磁阻效应的油位传感器
CN102768057A (zh) * 2012-07-06 2012-11-07 广东美的制冷设备有限公司 一种水位开关及水位信号检测装置
CN203083663U (zh) * 2013-01-25 2013-07-24 江苏多维科技有限公司 数字液位传感器
CN103105216A (zh) * 2013-01-29 2013-05-15 佛山市川东磁电股份有限公司 一种磁敏传感器及其制造工艺
CN203053525U (zh) * 2013-01-29 2013-07-10 佛山市川东磁电股份有限公司 一种mr磁阻磁敏传感器

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP2950060A4 *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11035716B2 (en) 2013-01-25 2021-06-15 MultiDimension Technology Co., Ltd. Digital liquid-level sensor having at least one tunneling magnetoresistance switch
JPWO2016163171A1 (ja) * 2015-04-06 2018-01-11 株式会社村田製作所 液面検出装置
EP3282232A4 (en) * 2015-04-06 2018-10-31 Murata Manufacturing Co., Ltd. Liquid surface detection device
EP3304010B1 (fr) * 2015-05-29 2021-12-15 Safran Aircraft Engines Capteur de niveau d'huile
WO2020177595A1 (zh) 2019-03-04 2020-09-10 江苏多维科技有限公司 一种基于磁阻传感器交叉点阵列的数字液位传感器
EP3936834A4 (en) * 2019-03-04 2022-12-14 MultiDimension Technology Co., Ltd. DIGITAL LIQUID LEVEL SENSOR BASED ON A MAGNETORESISTIVE SENSOR CROSSPOINT TARRAY

Also Published As

Publication number Publication date
EP2950060B1 (en) 2022-04-06
US20150355014A1 (en) 2015-12-10
US11035716B2 (en) 2021-06-15
EP2950060A1 (en) 2015-12-02
JP6215961B2 (ja) 2017-10-18
CN103968918B (zh) 2018-11-09
CN103968918A (zh) 2014-08-06
JP2016508598A (ja) 2016-03-22
EP2950060A4 (en) 2016-11-09

Similar Documents

Publication Publication Date Title
WO2014114259A1 (zh) 数字液位传感器
US10240961B2 (en) Electronic water meter
EP0595553B1 (en) Improvements in and relating to position responsive apparatus
CN102129053B (zh) 一种基于巨磁电阻效应的测量磁场方向和强度的传感器
CN101238378B (zh) 三相电流传感器
ATE289419T1 (de) Magnetfeldfühler und verfahren zu ihrer herstellung
CN110007133B (zh) 一种数字化交直流电流传感器及电流检测方法
CN105675092A (zh) 一种微型高精度液位传感器
CN101750102A (zh) 磁电旋转编码器以及磁电式的旋转角度测量方法
EP0415195A1 (en) Hall effect signalling gauge
JP2023545311A (ja) 油圧シリンダの伸び量検出装置
CN201463826U (zh) 一种磁阵列位置传感装置
CN108195442A (zh) Tmr液位传感器
CN1243247C (zh) 一种电流传感器
CN113701615A (zh) 位置传感器及位置检测装置
WO2020204462A1 (ko) 정전용량 방식을 이용하여 수위를 측정하기 위한 장치 및 그 방법
EP1113277B1 (en) A bushing element for medium and high voltage applications
CN203083663U (zh) 数字液位传感器
WO2018085987A1 (en) Unipolar resistive ladder sensor
CN111487044B (zh) 变倍镜头
CN207703894U (zh) 用于标准动车组三轴平稳舒适检测的加速度传感器装置
CN209342150U (zh) 一种微型远传温度、液位传感器
CN2909179Y (zh) 磁阻式直读表头
CN210005023U (zh) 一种仪表计量信号采样结构
WO2024058559A1 (ko) 자기장을 이용한 압력 센서

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 14742929

Country of ref document: EP

Kind code of ref document: A1

ENP Entry into the national phase

Ref document number: 2015554042

Country of ref document: JP

Kind code of ref document: A

WWE Wipo information: entry into national phase

Ref document number: 14763431

Country of ref document: US

NENP Non-entry into the national phase

Ref country code: DE

REEP Request for entry into the european phase

Ref document number: 2014742929

Country of ref document: EP

WWE Wipo information: entry into national phase

Ref document number: 2014742929

Country of ref document: EP