Liquid level sensor and measuring method thereof
Technical field
The application relates to a kind of liquid level sensor, can be used for measuring the liquid level of various liquid.
Background technology
At liquid level detection field, there are a variety of measurement means.Adopt at present many liquid level sensors to comprise variable resistance type, dry-reed, magnetostriction type etc.
Variable resistance type liquid level sensor is that a float is placed in liquid and makes it swim in all the time liquid surface, and this float is also connecting the sliding end of slide rheostat.Float is along with liquid level raises together or reduces, and the sliding end of the slide rheostat being connected with float is motion thereupon also, thereby just can learn height of liquid level by detecting the resistance of slide rheostat.
Variable resistance type liquid level sensor has following shortcoming:
One, the possibility that exists slide rheostat to contact with fluid to be measured.If fluid to be measured has certain electric conductivity, can affect liquid level sensor measuring accuracy, even make liquid level sensor lose efficacy.
Its two, the sliding end of slide rheostat is after long-term use, can there is variation to a certain degree in its contact resistance, thereby affect measuring accuracy.
Its three, resistance and the temperature of slide rheostat are closely related, do not change, thereby affect measuring accuracy even if liquid level changes because temperature variation also can cause the resistance of slide rheostat.
Dry-reed liquid level sensor is that a float with magnet is placed in liquid and makes it swim in all the time liquid surface, is also provided with a plurality of tongue tubes (Reed Switch also claims reed capsule, magnetic reed switch) that are positioned on differing heights.Float is along with liquid level raises together or reduces, and the magnet on float can make to be positioned at the tongue tube adhesive of corresponding height, and the tongue tube on all the other height all flicks.Only need all tongue tube contact resistances, then by measured resistance value, can learn which tongue tube is closed, thereby learn height of liquid level.
Dry-reed liquid level sensor has been realized the isolation of measuring sensor and fluid to be measured, i.e. non-contact measurement liquid level, thereby there is not short-circuit risks.But if dry-reed liquid level sensor arranges sparsely by tongue tube, can cause measuring accuracy not enough; If tongue tube is arranged intensively, the magnet on float will make near a plurality of tongue tube adhesives of certain height simultaneously so, can cause equally measuring accuracy limited.
The structure of Liquid Level Sensor Based on Magnetostriction and principle of work are as described in " instrumental technique and sensor " periodical article " Liquid Level Sensor Based on Magnetostriction " of the 12nd phase in 2007, the article " application of magnetostrictive liquid level sensor and development " of " mining and metallurgy " periodical the 13rd the 4th phase of volume of Dec in 2004.It has, and non-contact measurement liquid level, precision are high, the feature of stable performance.But have the blind area that cannot detect, and manufacturing process is complicated, cost is higher.
Summary of the invention
The application's technical matters to be solved is to provide a kind of novel high-accuracy liquid level sensor, adopts measuring sensor to measure the liquid level of fluid to be measured contactlessly.
For solving the problems of the technologies described above, the application's liquid level sensor comprises:
---housing, its inside crosses an airtight cavity, in this airtight cavity, is fixed with photoelectric sensor, and this photoelectric sensor is comprised of optical transmitting set and optical receiver two parts;
---controller, be positioned at described airtight cavity, the output shaft of Driving Stepping Motor produces angular displacement, and calculates liquid level;
---stepper motor, be positioned at described airtight cavity, there is an output shaft; The output pulse of often receiving controller, motor output shaft just rotates fixed angle;
---detection dish, be positioned at described airtight cavity, be fixed on motor output shaft, and follow motor output shaft and rotate together; On detection dish, be fixed with catch and detecting element, detecting element is the Hall element of two same specifications, be fixed on mutually near and with the position of detecting the Pan center of circle and have same distance;
---pedestal, be fixed on outside, on pedestal, be fixed with rotationally float fulcrum pin, on float fulcrum pin, be fixed with un-rotatably the first gear;
---float, swims in the surface of fluid to be measured; Float is fixed on float fulcrum pin by float lever;
---rotary disk, be rotatably mounted to outside, rotary disk has identical axial line with motor output shaft; At rotary disk, be provided with the second gear being meshed with the first gear, be also fixed with phase magnet; The distance in the center of circle of phase magnet center and rotary disk equals detecting element center and the distance that detects the Pan center of circle.
The measuring method of the application's liquid level sensor comprises the steps:
The 1st step, the work of controller Driving Stepping Motor, motor output shaft drives detection dish to rotate together, until the catch on detection dish has intercepted optical transmitting set and the optical receiver of photoelectric sensor, this is called as calibration steps;
The 2nd step, the work of controller Driving Stepping Motor, motor output shaft drives detection dish to rotate together, until the detecting element on detection dish is aimed at the phase magnet on rotary disk, this is called as measuring process;
The 3rd step, controller according to the angular displacement of the motor output shaft between calibration steps and measuring process or between twice measuring process or detection dish or according to controller the number of pulses to stepper motor output, calculate the height of liquid level of fluid to be measured.
The application's liquid level sensor tool has the following advantages:
One, inclusion test element all can be arranged in the cavity of watertight at interior electric component, realizes the contactless level gauging to fluid to be measured, thereby can be applied to level gauging inflammable, explosive and highly corrosive liquid.
Its two, detecting element is comprised of two Hall elements of same specification, only has the output valve of these two Hall elements identical (line style) or all change level state (switching mode) and just think and aimed at float magnet.Hall element by two same specifications can be realized high-precision level gauging to the detection of same magnet, and can compensation temperature etc. the impact of change of external conditions.
Its three, compare with Liquid Level Sensor Based on Magnetostriction, the application's liquid level detects except having similar high precision, has detection non-blind area, little, the easy installation of volume, the feature such as with low cost simultaneously.
Its four, compact to design, stable performance, can work reliably and with long-term.
Accompanying drawing explanation
Fig. 1 is the structural representation of the application's liquid level sensor;
Fig. 2 is the float position variable condition schematic diagram of observing along the arrow A direction in Fig. 1;
Fig. 3 is the process flow diagram of the measuring method of the application's liquid level sensor;
Fig. 4 is the process flow diagram of a specific embodiment of the measuring method of the application's liquid level sensor.
Description of reference numerals in figure:
1 is housing; 10 is dividing plate; 11 is the first cavity; 12 is the second cavity; 13 is photoelectric sensor; 2 is controller; 3 is stepper motor; 30 is motor output shaft; 4 is detection dish; 41 is catch; 42 is detecting element; 5 is pedestal; 50 is float fulcrum pin; 51 is the first gear; 6 is float; 60 is float lever; 7 is rotary disk; 71 is spring; 72 is the second gear; 73 is phase magnet; 8 is photoelectric encoder (optional).
Embodiment
Refer to Fig. 1 and Fig. 2, the application's liquid level sensor comprises:
---housing 1, its inside has crossed an airtight cavity.In this airtight cavity inside, by dividing plate 10 Further Divisions, be the first cavity 11 and the second cavity 12 again.On dividing plate 10, be fixed with photoelectric sensor 13, this photoelectric sensor 13 is comprised of optical transmitting set and optical receiver two parts.
---controller 2, such as being single-chip microcomputer, PLC(programmable logic controller (PLC)) etc., be arranged in the first cavity 11.This controller 2 is exported pulses with the output shaft 30 generation angular displacements of control step motor 3 to stepper motor 3 on the one hand, calculates on the other hand the liquid level of fluid to be measured according to the angular displacement of the output shaft 3 of stepper motor 3.
---stepper motor 3, is arranged in the first cavity 11.It has an output shaft 30 and passes through dividing plate 10.An output pulse of often receiving controller 2, the output shaft 30 of stepper motor 3 just produces fixing angular displacement (rotating fixing angle).Output pulse is divided into and rotates and reverse two types, and during controller 2 output forward pulse, motor output shaft 30 rotates along a direction, for example clockwise direction; During controller 2 output inversion pulse, motor output shaft 30 rotates along another direction, for example counterclockwise.During practical application, the segmentation step number that only need to increase stepper motor 3 can improve accuracy of detection effectively.
---detection dish 4, is arranged in the second cavity 12.It is fixed on motor output shaft 30, and follows motor output shaft 30 and rotate together.On detection dish 4, be fixed with catch 41 and detecting element 42.When detection dish 4 turns to special angle, catch 41 can be between optical transmitting set and optical receiver, and now photoelectric sensor 13 can detect catch 41.Detecting element 42 is Hall elements of two same specifications, is close on the circumference that is fixed on detection dish 4, and the center of circle of these two Hall elements and detection dish 4 has same distance.
---pedestal 5, is fixed on the outside of housing 1.On pedestal 5, be fixed with rotationally float fulcrum pin 50, on float fulcrum pin 50, be fixed with un-rotatably the first gear 51.The first gear 51 is followed float fulcrum pin 50 and is rotated together, but there is no relative motion between the first gear 51 and float fulcrum pin 50.
---float 6, swims in the surface of fluid to be measured.Float 6 is fixed on float fulcrum pin 50 by the fixing float lever 60 of length.When the liquid level of fluid to be measured changes, float lever 60 rotates drive float fulcrum pin 50, the first gear 51 together with respect to pedestal 5.
---rotary disk 7, is rotatably mounted to the outside of housing 1.The axle center of rotary disk 7 is on the axes extending line of motor output shaft 30, and rotary disk 7 has identical axial line with motor output shaft 30 in other words.On rotary disk 7, be axially provided with spring 71 and the second gear 72.Spring 71 is arranged between rotary disk 7 and housing 1, for making the second gear 72 and first gear 51 of rotary disk 7 opposite sides compress also intermeshing.On rotary disk 7, be also fixed with phase magnet 73.Phase magnet 73 is fixed on the circumference of rotary disk 7, and the distance in the center of circle of phase magnet 73 centers and rotary disk 7 equals the distance in the center of circle of detecting element 42 centers and detection dish 4.
Hall element is a kind of element of measuring magnetic induction density, is divided into two kinds of line style and switching modes.In its sensing range, line style Hall element is nearer apart from magnet, and the magnetic induction density measuring is larger; Vice versa.Hall switch sensor is exported a kind of level state (for example high level) at ordinary times, only apart from magnet compare Jin region, is just switching to output another kind of level state (for example low level).
In the application, photoelectric sensor 13 and catch 41 have formed a zero position device.When catch 41 is not between the optical transmitting set of photoelectric sensor 13 and optical receiver, the optical receiver of photoelectric sensor 13 can receive the signal of optical transmitting set.When catch 41 is between the optical transmitting set of photoelectric sensor 13 and optical receiver, the optical receiver of photoelectric sensor 13 cannot receive the signal of optical transmitting set.Based on this feature, can be used for carrying out position correction.
In the application, detecting element 42 is Hall elements of two same specifications.When it is the line style Hall element of two same specifications, the position that these two Hall elements detect identical magnetic induction density is exactly the position of aiming at phase magnet 73.When it is the Hall switch sensor of two same specifications, the position that level state of these two Hall elements all changes is exactly the position of aiming at phase magnet 73.
The measuring principle of the application's liquid level sensor is: along with liquid level rising or the reduction of fluid to be measured, the position of float 6 also increases or reduces, and this rotates float lever 60 together with float fulcrum pin 50 with respect to pedestal 5.Driven the first gear 51 being fixed on float fulcrum pin 50 to rotate simultaneously.Due to the meshing relation between the second gear 72 and the first gear 51, drive again the second gear 72 to rotate simultaneously, make rotary disk 7 rotate.Obviously, when the liquid level of fluid to be measured raises, rotary disk 7 will rotate along a direction, for example clockwise direction; When the liquid level of fluid to be measured reduces, rotary disk 7 will rotate along another direction, for example counterclockwise.Controller 2 is by the rotation of the output shaft 30 of control step motor 3, in the time of can making the phase magnet 73 on the detecting element 42 aligning rotary disks 7 on detection dish 4, now the angular displacement of motor output shaft 30 is just equal to the angular displacement of rotary disk 7, can learn the liquid level of fluid to be measured by converting.
Refer to Fig. 3, the measuring method of the application's liquid level sensor comprises the steps:
The 1st step, controller 2 Driving Stepping Motor 3 work, motor output shaft 30 drives detection dish 4 to rotate together, until the catch 41 on detection dish 4 has stopped the signal of photoelectric sensor 13, this is called as calibration steps, and the signal of now photoelectric sensor 13 outputs is called as zero signal.Calibration steps only need to carry out once at every turn after powering on.
Obviously, catch 41 installation site should be corresponding with photoelectric sensor 13 installation site, to guarantee that when detection dish 4 turns to special angle catch 41 can fully intercept optical transmitting set and the optical receiver of photoelectric sensor switch 13.
The 2nd step, controller 2 Driving Stepping Motor 3 work, motor output shaft 30 drives detection dish 4 to rotate together, until the phase magnet 73 that the detecting element 42 on detection dish 4 is aimed on rotary disk 7, this is called as measuring process.Because detecting element 42 is comprised of the Hall element of two same specifications, therefore only has phase magnet 73 simultaneously in the sensing range of these two Hall elements and when identical with the distance of these two Hall elements, these two Hall elements just can have identical output (if line style) or all change to identical level state (if switching mode).Therefore the detecting element 42 consisting of two Hall elements has just had very high accuracy of detection.When the external conditions such as temperature, voltage change, its impact on the Hall element of these two same specifications is consistent, still can not affect the accuracy of detection of detecting element 42 after cancelling out each other.
Because detection dish 4 and rotary disk 7 have same axial line, detecting element 42 equals the distance in the center of circle of phase magnet 73 and rotary disk 7 with the distance in the center of circle of detection dish 4, so can guarantee that detecting element 42 is at a certain position alignment phase magnet 73.
The 3rd step, controller 2 is according to motor output shaft 30(or detection dish 4) angular displacement between from calibration steps to measuring process or from last measuring process to the angular displacement this measuring process, calculate the height of liquid level of fluid to be measured, this can draw by trigonometric function formula.
The number of pulses of exporting to stepper motor 3 due to controller 2 is mutually corresponding with the angular displacement of the output shaft 30 of stepper motor 3, the liquid level that pulse pattern (forward pulse, inversion pulse) that controller 2 also can be exported to stepper motor 3 according to it and number of pulses calculate fluid to be measured.
If carrying out carrying out again measuring process for the second time after measuring process for the first time, controller 2 is according to motor output shaft 30(or detection dish 4 so) from measuring process for the first time to the angular displacement measuring process for the second time or according to controller 2 from measuring process for the first time to for the second time measuring process to pulse pattern and the number of pulses of stepper motor 3 outputs, can calculate the height of liquid level of fluid to be measured.
Or, also can adopt sensor (photoelectric encoder 8 as shown in phantom in Figure 1) directly to measure detection dish 4(or motor output shaft 30) angular displacement and pass to controller 2.
Refer to Fig. 4, this is a specific embodiment of the measuring method of the application's liquid level sensor, and its middle controller 2 is every to a pulse signal of stepper motor 3 outputs, and motor output shaft 30 just rotates fixed angle.For example, forward pulse, inversion pulse correspond respectively to motor output shaft 30 clockwise, rotate counterclockwise.First, controller 2 Driving Stepping Motors 3 are worked, for example, export all the time the pulse signal of same type, until photoelectric sensor 13 output zero signals.Secondly, controller 2 is to the pulse signal of one type of stepper motor 3 output, until two Hall elements of detecting element 42 have output.Controller 2 is further adjusted type, the quantity of output pulse, until two Hall elements of detecting element 42 have identical output.Finally, controller 2, according to type and the quantity of all output pulses in measuring process, calculates the height of liquid level of fluid to be measured.
These are only the application's preferred embodiment, and be not used in restriction the application.For a person skilled in the art, the application can have various modifications and variations.All within the application's spirit and principle, any modification of doing, be equal to replacement, improvement etc., within all should being included in the application's protection domain.