CN102445252B - Resistor type water-level digital sensor - Google Patents

Resistor type water-level digital sensor Download PDF

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Publication number
CN102445252B
CN102445252B CN2011104131287A CN201110413128A CN102445252B CN 102445252 B CN102445252 B CN 102445252B CN 2011104131287 A CN2011104131287 A CN 2011104131287A CN 201110413128 A CN201110413128 A CN 201110413128A CN 102445252 B CN102445252 B CN 102445252B
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CN
China
Prior art keywords
circuit
electrode
bending
voltage
resistance
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CN2011104131287A
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Chinese (zh)
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CN102445252A (en
Inventor
李玉柱
闵俊杰
孟春亚
高吭
姜烈伟
贺智涛
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河南科技大学
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Abstract

A resistor type water-level digital sensor belongs to the field of water-level sensors, which comprises a testing circuit and a measurement probe essentially formed by an insulation round pipe, a straight electrode and a bent electrode. The upper end and the lower end of the insulation round pipe are respectively provided with a fixing plug. The lower fixing plug is provided with a water feeding hole communicated with a cavity of the insulation round pipe, and the upper fixing plug is provided with a vent. The bottom ends of the straight electrode and the bent electrode are arranged in the insulation round pipe and fixed on the lower fixing plug. The bent portion of the bent electrode is arranged in the insulation round pipe, and the upper ends of the straight electrode and the bent electrode penetrate the upper fixing plug to be provided with an extending end respectively. The testing circuit of the resistor type water-level digital sensor combines a resistor property of the probe, and enables an observation quantity obtained by the circuit to be in primary linear relationship with height of water levels so as to satisfy continuous equal-accuracy measurement of the water levels.

Description

A kind of resistance type water level digital sensor

Technical field

The invention belongs to the water level monitoring sensor field, especially relate to a kind of resistance type water level digital sensor.

Background technology

At present, the level sensor kind is a lot of on the market, useful ultrasound wave principle, capacitance principle, thermal resistance, tongue tube or the like, and still: the sensor of ability continuous coverage but costs an arm and a leg; Otherwise be exactly that noncontinuity is measured, precision is low.With will the reaching measuring accuracy more measurement lattice point need be installed of the point measurement that fixes, cause complex structure, cost increases.With water resistance a lot of as measuring principle, but most of sensors all can not continuous coverage on the market, and it is very big with the variation drift of water quality to record height value.

Summary of the invention

The objective of the invention is deficiency for solving the problems of the technologies described above; A kind of resistance type water level digital sensor is provided, and measuring sonde is simple in structure, and is with low cost; Test circuit has combined the resistance characteristic of probe; Make the observed quantity and the height of water level of circuit picked-up be once linear relationship, thereby satisfy the continuous equal precision measurement of water level, when water level touches the extreme position of sensor at every turn; The inside of sensor can once revised and be stored in to the sensing data processing unit to the coefficient of once linear relationship formula, guaranteed that the slow variation of water resistance rate can not cause the drift that records height.

The present invention is the deficiency that solves the problems of the technologies described above, and the technical scheme that is adopted is: a kind of resistance type water level digital sensor comprises test circuit; Also be provided with measuring sonde; Described measuring sonde mainly is made up of insulation pipe, straight electrode and bending electrode, and the two ends up and down of insulation pipe are equipped with fixing plug, the fixing down inlet opening that is communicated with insulation pipe inner chamber that is provided with beyond the Great Wall; At the last fixing vent port that is provided with beyond the Great Wall; The bottom of straight electrode and bending electrode is arranged in the insulation pipe and is fixed on down that fixing the bending part of bending electrode is arranged in the pipe that insulate beyond the Great Wall, and the upper end of straight electrode and bending electrode passes fixedly that plug has external part respectively;

Described bending electrode is made up of the bending part and the following connecting portion of last connecting portion, level, and last connecting portion is connected with the bending part two ends respectively with following connecting portion, and bending part is 90 ° with the angle of the junction of following connecting portion.

Described test circuit is made up of probe resistance detecting circuit and digital signal processing circuit; Two output terminals of measuring sonde are connected in the probe resistance detecting circuit; The data-signal supplied with digital signal processing circuit processes of probe resistance detecting circuit calculates the height of water level through detecting the measuring sonde change in current.

Said probe resistance detecting circuit is made up of than negative-feedback circuit, measuring voltage amplifying circuit and filtering circuit constant-current source circuit, AC signal driving circuit, voltage ratio.

The invention has the beneficial effects as follows: this digital sensor adopts measuring sonde and test circuit to constitute, and measuring sonde is simple in structure, and is with low cost; Test circuit has combined the resistance characteristic of probe cleverly, makes the observed quantity and the height of water level of circuit picked-up be once linear relationship, thereby satisfies the continuous equal precision measurement of water level.When water level touched the extreme position of sensor at every turn, the inside of sensor can once revised and be stored in to the sensing data processing unit to the coefficient of once linear relationship formula, guaranteed that the slow variation of water resistance rate can not record the drift of height together.

Description of drawings

Fig. 1 is the structural representation of measuring sonde among the present invention.

Fig. 2 is the structural representation of bending electrode in the measuring sonde.

Fig. 3 is the circuit diagram of probe resistance detecting circuit among the present invention.

Fig. 4 is the constant-current source circuit figure among the present invention.

Fig. 5 is the AC signal driving circuit figure among the present invention.

Fig. 6 for the voltage ratio among the present invention than negative-feedback circuit figure.

Fig. 7 is the measuring voltage amplification circuit diagram among the present invention.

Fig. 8 is the filtering circuit figure among the present invention.

Fig. 9 is the digital signal processing circuit figure among the present invention.

Reference numeral: 1, insulation pipe, 2, straight electrode, 3, the bending electrode, 301, go up connecting portion, 302, bending part, 303, connecting portion down, 4, fixing plug down, 401, the inlet opening, 5, go up fixing plug, 501, vent port.

Embodiment

As shown in the figure; A kind of resistance type water level digital sensor is made up of measuring sonde and test circuit, and two output terminals of measuring sonde insert in the test circuit as sensor resistance; Described measuring sonde mainly is made up of insulation pipe 1, straight electrode 2 and bending electrode 3; The two ends up and down of insulation pipe 1 are equipped with fixing plug, and down fixing plug 4 is provided with the inlet opening 401 that is communicated with insulation pipe inner chamber, on last fixing plug 5, are provided with the vent port 501 with the pipe intracavity inter-connection that insulate; The bottom of straight electrode 2 and bending electrode 3 is arranged in the insulation pipe and is fixed on down on the fixing plug 4; The bending part 302 of bending electrode 3 is arranged in the insulation pipe 1, and the upper end of straight electrode 2 and bending electrode 3 is passed fixing plug 5 and had external part respectively, is used to test out the height change of water level through two external parts are connected with test circuit.

Described bending electrode 3 is made up of the bending part 302 and the following connecting portion 303 of last connecting portion 301, level, and last connecting portion 301 is connected with bending part 302 two ends respectively with following connecting portion 303, and bending part 302 is 90 ° with the angle of the junction of following connecting portion 303.

Measuring principle is following: sonde configuration comprises fixing up and down plug, insulation pipe, bending electrode and straight electrode; Fix the two electrodes fixed effect of having filled in up and down; Wherein the bending electrode is allowing water level highest point bending (frustrating the chamfering except that bending part), the bending part parallel axes and the water surface at sensor.When water level reaches maximum position and contacts with bending electrode bending part, cause once becoming more of two resistance between electrode, measuring voltage adopts alternating current, the polarization of anti-sealing.When water level has just overflowed following stopple and two electrodes of UNICOM is minimum measurement point, and be R0 this moment between two resistance between electrode; For measuring maximum height, this moment, two resistance between electrode were Rt during water level rising H0 contact bending electrode curved boom.When water level whenever increased Δ h, the right cylinder water column two interelectrode resistance in the Δ h height were Rh, then have:

When adding a constant voltage U0 at this Resistance probe, the electric current I t of the Rt that flows through and the relational expression of water column are:

Rh, R0, U0 are not constant when the water quality short time does not change.So water colunm height H becomes once linear relationship with the electric current I t of the probe of flowing through.Only measure It and can obtain corresponding height of water level., water level all can cause the sudden change of resistance when just having overflowed following stopple or reached maximum position; Because the position height value at this place; And can once revise above-mentioned pass formula coefficient, and store, thereby avoided because the measuring height value drift that the slow variation of water quality or electrode causes.Need pop one's head in during use before use fully in the invasion water once, so that measuring junction obtains the coefficient of once linear relationship formula.The level measuring that this single-unit probe is applicable to that water level often changes and always fluctuates in minimum value and maximal value, as: solar water heater, the small-sized water tower of family etc.

Described test circuit is made up of probe resistance detecting circuit and digital signal processing circuit; Two output terminals of measuring sonde are connected in the probe resistance detecting circuit; The data-signal supplied with digital signal processing circuit processes of probe resistance detecting circuit calculates the height of water level through detecting the measuring sonde change in current.The probe resistance detecting circuit is made up of than negative-feedback circuit, measuring voltage amplifying circuit and filtering circuit constant-current source circuit, AC signal driving circuit, voltage ratio.

Said constant-current source circuit is to have unit U0 (2), U0 (3) and resistance R 3, R4, R9, R10, R11, RS and sensor resistance RL in the operational amplifier to form; R4/R3=R9/R10 wherein, the size of electric current equals the ratio of R4 input voltage and resistance value RS in the circuit.When sensor probe resistance seals in this circuit loop, through the flow through electric current of sensor resistance of the indirect measurement of the forward voltage of measure R 4.

Said AC signal driving circuit is to have operational amplifier U2 and resistance R 13 ~ 21 to form, and wherein R20 and R18 form single-chip microcomputer P3.3 mouth divider resistance; R21 and R19 form single-chip microcomputer P3.4 mouth divider resistance; R13 and R16 resistance equate that this circuit is accomplished power that increases input signal and the alternating voltage that produces positive and negative variation.

Said voltage ratio has been meant operational amplifier U0 (4) than negative-feedback circuit, and resistance R 12, R14, R15, R7 and capacitor C 3 are formed.R12 and R15 have determined the negative feedback enlargement factor, and resistance R 7 and capacitor C 3 have determined the response speed of this feedback, and this circuit is mainly accomplished the alternating voltage that forces the sensor probe on-load voltage to equal the output of AC signal driving circuit.

Said measuring voltage amplifying circuit is to have operational amplifier U0 (1) and resistance R 5, R6, R8 to form.It accomplishes the voltage amplification of resistance R 4 input ends.

Said filtering circuit group is meant two-way (supply voltage and R4 rectify to voltage) the low pass signal filtering circuit of being made up of resistance R 1, C1 and R2, C2, disturbs for metering circuit reduces.

Digital signal processing circuit has been meant: STC12C5201AD single-chip minimum system and resistance R 23, diode D0 form.The STC12C5201AD single-chip microcomputer is realized the generation of AC signal, simultaneously through control I/O port; When this AC signal is positive voltage; Measure the voltage that is carried in the R4 end through self 10 integrated ultra high speed A, handle through its data again, accomplish measurement water level.Wherein the inner volume EEPROM of single-chip microcomputer has write down data such as electrical conductivity of water.Wherein resistance R 23, diode D0 form the reference voltage of systematic survey.

Said test circuit principle of work is following:

RL is the probe resistance value.Unit U0 (2), U0 (3) and resistance R 3, R4, R9, R10, RS form a current source among the operational amplifier LM324, and be as shown in Figure 4.Wherein , the size of electric current equals the ratio of R4 input voltage and resistance value RS.The output of the current source resistance R 11 of connecting, and connect probe resistance R L one end, another termination simulation ground of RL.The resistance of RS is constant, so the size of the RL that flows through is determined analog ground voltage Ue by input R4 left end.

Operational amplifier U0 (4) and resistance R 12, R15, R7 form the voltage negative feedback circuit of probe resistance R L pressurization, and be as shown in Figure 6.R4 is given in voltage difference (voltage difference of R14 left end voltage and RL end) negative feedback after amplifying through U0 (4), and makes the on-load voltage of RL identical with R14 left end voltage through the electric current of regulating constant-current source circuit.R11 is the build-out resistor of RL, and is too small in order to avoid sensor resistance to change, and causes influencing the work of circuit.Capacitor C 3 and R7 avoid the concussion of feeding back, and improve system responses and stabilized speed, reduce the stable time of RL terminal voltage.The enlargement factor of U0 (4) has also determined the precision of systematic survey.Realized at a forward voltage that through voltage negative feedback circuit sensor probe resistance is constant to analog ground voltage in measuring period, thereby the electric current that only detects the RL that flows through just can be extrapolated the height of water level.Wherein R12 has shunting action to constant current source, but sensor probe resistance R L on-load voltage value is constant, so the size of current of the R12 that flows through is constant, deducts this current component during system-computed.

For guaranteeing that water is not polarized; Need make the electric current that is carried in RL can produce alternation; So be made up of the voltage of big or small alternation such as a positive and negative equal time passes to U0 (4) positive terminal through R14 and does reference voltage U2 and R13, R16, R17, R18, R19, R20, R21; Form the AC signal driving circuit, as shown in Figure 5.Because the effect of voltage negative feedback circuit, force to be carried in the ohmically magnitude of voltage of sensor probe and to equal R14 terminal voltage value.Single-chip microcomputer is through control I/o P3.3 and P3.4 height potential change, again through realizing three kinds of variation :+2V of the reference voltage of R4 end among R16, the R17 input U2;-2V and 0V.Consider the error of resistance and single-chip microcomputer I/o actuation voltage value; The voltage that very difficult assurance is carried in RL for+2V ,-2V and 0V; So system has monitored the voltage of reference voltage R14 end simultaneously; So that late time data obtains higher precision when handling, accurate simultaneously control 2V ,-2V and logical time of 0V electric current and voltage, the polarization of anti-sealing.Systematic survey only carries out during for+2V at reference voltage.

System is through reading the size of R4 left end Ue voltage, and can try to achieve the height of water level according to the once linear relationship formula.Because the system works electric current is very little, voltage drop value is too little on R4, is total to single chip computer measurement so need zoom into the voltage of volt level.The voltage measurement amplifying circuit of R4 is as shown in Figure 7, is made up of operational amplifier U0 (1) and resistance R 5, R6, R8.

Have the signal of measuring voltage amplifying circuit output after filtering circuit filtering, to send into Chip Microcomputer A conversion mouth, it is by the two paths of signals low-pass filter circuit that resistance R 1, C1 and R2, C2 form, and is as shown in Figure 8.One the tunnel connects the output of R4 terminal voltage amplifying circuit, and one the tunnel connects the output of sensor supply voltage detection signal.Receive the interference of power-supply fluctuation through filtering circuit reduction system.

Because of the AD digital-to-analog conversion is to wait the differential conversion to Ue, the relational expression that once rolls off the production line has guaranteed that height of water level also is to wait differential to change, and promptly measuring accuracy is identical to measured value at any height of sensor probe place.

Said digital signal processing circuit is as shown in Figure 9.Its core is made up of a STC12C5201AD and minimum system circuit thereof.The P1 mouth is 8 tunnel 10 ultra high speed A interfaces.Its conversion reference voltage is a chip power supply voltage.Consider whether system's power supply is stable voltage, so add a reference voltage, its circuit has resistance R 23 and D0 diode (silicone tube, pressure drop 0.7V).Voltage through conversion D0 end standard comes the comparison system supply voltage, calculates Ue voltage more accurately.Resistance R 18 ~ 21 is got suitable resistance, and when single-chip microcomputer P3.3 and P3.4 were low level, the positive and negative phase terminal voltage of input U2 all was 3V.The U2 enlargement factor is 1.Put when high when P3.3 puts low, P3.4, R14 left end voltage (RL holds reference voltage) is 2V; When P3.3 puts height, R14 left end voltage was-2V when P3.4 put and hangs down; When P3.3 and P3.4 were high, R14 left end voltage was 0V, and test circuit stops test.Three kinds of cycle of states are with electricity, the survey frequency decision that+2V and-2V time conduction time basic identical (program specifically being arranged according to time magnitude of voltage decision), 0V have the user to import the conduction time.

This sensing data processing unit is through reading the numerical value of Ue; Through the positional value that changes behind the digital filtering and according to the known geometric electrode parameter of sensor; Combine to obtain the coefficient that Ue suddenlys change, contrasts the once linear relationship formula of match height of water level and electric current again; Revise near the height of water level value of sudden change place, reach accurate measurement water level.Simultaneously coefficient value is stored among the EEPORM of chip.This sensor is known because of the electrode change location, and data processing unit is checked electrical conductivity of water under this sensor automatically, so need not to demarcate.

This digital sensor transmits water level value for the use machine through the standard serial port agreement, and the use machine can be through the frequency of serial ports control survey.For SEA LEVEL VARIATION slowly or real-time to require be not too high occasion, can reduce observing frequency as far as possible, to reduce the polarization of water, prolong sensor accuracy and life-span.

Claims (3)

1. resistance type water level digital sensor; Comprise test circuit; It is characterized in that: also be provided with measuring sonde; Described measuring sonde mainly is made up of insulation pipe (1), straight electrode (2) and bending electrode (3), and the two ends up and down of insulation pipe (1) are equipped with fixing plug, and fixing plug (4) is provided with the inlet opening (401) that is communicated with insulation pipe inner chamber down; On last fixing plug (5), be provided with vent port (501); The bottom of straight electrode (2) and bending electrode (3) is arranged in the insulation pipe and is fixed on down on the fixing plug (4), and the bending part (302) of bending electrode (3) is arranged in the insulation pipe (1), and the upper end of straight electrode (2) and bending electrode (3) is passed fixing plug (5) and had external part respectively;
Described bending electrode (3) is made up of the bending part (302) and the following connecting portion (303) of last connecting portion (301), level; Last connecting portion (301) is connected with bending part (302) two ends respectively with following connecting portion (303), and bending part (302) is 90 ° with the angle of the junction of following connecting portion (303).
2. a kind of resistance type water level digital sensor according to claim 1; It is characterized in that: described test circuit is made up of probe resistance detecting circuit and digital signal processing circuit; Two output terminals of measuring sonde are connected in the probe resistance detecting circuit; The data-signal supplied with digital signal processing circuit processes of probe resistance detecting circuit calculates the height of water level through detecting the measuring sonde change in current.
3. a kind of resistance type water level digital sensor according to claim 2 is characterized in that: said probe resistance detecting circuit is made up of than negative-feedback circuit, measuring voltage amplifying circuit and filtering circuit constant-current source circuit, AC signal driving circuit, voltage ratio.
CN2011104131287A 2011-12-10 2011-12-10 Resistor type water-level digital sensor CN102445252B (en)

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CN102980634A (en) * 2012-06-07 2013-03-20 上海市七宝中学 Reed switch transducer control circuit for liquid-level measurement purpose
CN102928041B (en) * 2012-11-09 2015-11-18 国家海洋环境监测中心 Small size liquid level detector
DE102014223945A1 (en) * 2014-11-25 2016-05-25 Volkswagen Aktiengesellschaft A traction battery of an electric vehicle comprising a fluid detection system and method for detecting a fluid level in the traction battery
TWI564549B (en) * 2015-07-08 2017-01-01 桓達科技股份有限公司 Radar liquid level measuring apparatus and radar liquid level measuring method
CN106679763B (en) * 2016-12-27 2019-04-19 西北工业大学 A kind of mariages separation resistance-type molten metal bath liquid level sensor
CN109856578A (en) * 2018-12-10 2019-06-07 国家海洋技术中心 Conductivity sensor field calibration method based on three electrode conductance ponds

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CN2519903Y (en) * 2001-12-28 2002-11-06 王晓峰 Liquid level sensor
JP2010038550A (en) * 2008-07-31 2010-02-18 Nippon Seiki Co Ltd Liquid level detection device
CN102087119B (en) * 2010-03-18 2012-09-05 上海海事大学 Remote zero setting circuit and method for resistance-type strain measurement
CN201945637U (en) * 2010-12-31 2011-08-24 房慧龙 Resistance tester with wide temperature range, wide measuring range, high precision and low cost
CN202362048U (en) * 2011-12-10 2012-08-01 河南科技大学 Resistance-type water level digital sensor

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