CN102353429A - High-precision performance detector of resonant mode water level sensor and test method thereof - Google Patents
High-precision performance detector of resonant mode water level sensor and test method thereof Download PDFInfo
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- CN102353429A CN102353429A CN 201110240959 CN201110240959A CN102353429A CN 102353429 A CN102353429 A CN 102353429A CN 201110240959 CN201110240959 CN 201110240959 CN 201110240959 A CN201110240959 A CN 201110240959A CN 102353429 A CN102353429 A CN 102353429A
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Abstract
The invention relates to a high-precision performance detector of a resonant mode water level sensor and a test method thereof. In the high-precision performance detector, an air chamber pressure change is adopted to simulate an actual water level change; resonant mode water level sensor values in the air chamber are collected and then transmitted to a controller so as to be processed to obtain a sensor performance curve; and the change of air quantity in the air chamber is equal to that of a liquid level in a water tank. The high-precision performance detector can be used for completely eliminating the defects of low stability, low precision and high error of the traditional test system. In the invention, firstly, a novel high-precision frequency measuring method is utilized so that the frequency measuring error of the system is not more than +/-5 Hz and the system precision reaches a new level compared with the errors of dozens of hertz even hundreds of hertz in the traditional test system; secondly, the system is fitted by sampled data through using a least square method and the system output curve is extremely optimized, so that a performance test curve of the sensor is more approximate to a real curve; and finally, a processor chip with a high integration level is adopted so that the reliability of the system is also obviously improved.
Description
Technical field
The present invention relates to a kind of measuring instrument, particularly a kind of high precision Resonator water level sensor performance detector and method of testing.
Background technology
Resonator water level sensor plays significant role in fields such as industrial process control, automobile, environment and safety monitoring and military affairs.In practical application, level sensor is the important component part of data acquisition, and the quality of its performance will directly determine the data accuracy and the degree of accuracy of gathering.
Existing the Auto-Test System of various types of level sensor performances in the market, is that controller is main with PC or single-chip microcomputer mainly.But in the legacy system great majority all have a drawback be exactly stability and measuring accuracy lower.
Summary of the invention
The present invention be directed to the Auto-Test System stability and the lower problem of measuring accuracy of present level sensor performance; A kind of high precision Resonator water level sensor performance detector and method of testing have been proposed; Used the microcontroller of high integration to control core as system, system reliability also is highly improved.
Technical scheme of the present invention is: a kind of high precision Resonator water level sensor performance detector; Resonator water level sensor places in the sealed gas chamber that has the air inlet solenoid valve; The frequency that Resonator water level sensor output is measured arrives singlechip controller through amplifying circuit; Singlechip controller output control signal is through light-coupled isolation; Output to solenoid valve after amplifying through power amplification circuit again and air inlet of air chamber is opened and closed control, host computer adopts the communicating by letter of MATLAB tool implementation and slave computer singlechip controller, data processing and demonstration measurement result.
Said singlechip controller adopts the data acquisition chip AD μ C812 of U.S. ADI company as controller.
A kind of method of testing of high precision Resonator water level sensor performance detector comprises high precision Resonator water level sensor performance detector, specifically comprises the steps:
1) test beginning; Singlechip controller output signal is through light-coupled isolation; Output to solenoid valve after amplifying through power amplification circuit again; Open air chamber and begin air inlet; System begins air chamber pressure simultaneously and measures; The 1st force value of in recording force value and singlechip controller, setting equates that singlechip controller outputs a control signal to solenoid valve, closes air chamber and stops air inlet;
2) single-chip controller receives the resonant level sensor, start frequency measurement, initialize the timer and open the external interrupt 0, when the falling edge of the signal arrives, an interrupt is generated, the software gate to be opened simultaneously open counter 1 and counter 2 starts counting and related external interrupt 0, when the timer 0 timed to when (ie preset gate time T), opening the external interrupt 0, and this time the external interrupt counter 1 and counter 2 not stop counting until the measured signal falling edge, when the falling edge of the signal, the external interrupt 0 interrupt is generated, the synchronization off counter 1 and counter 2, the measured frequency of the signal can be expressed as:
,
is the measured signal frequency, M is the count value of the counter l, N is the Counter 2 count,
is the standard oscillator signal frequency;
3) will record the internal storage location that frequency values is saved in singlechip controller, the 1st point measurement finishes, repeating step 1) and 2) carry out 2 to 10 measurement;
4) 10 tests finish, and singlechip controller is successively sent in host computer through serial ports gained 10 dot frequency values;
5) host computer adopts the MATLAB instrument that frequency data are carried out the optimization process of sample frequency value, draws final Resonator water level sensor family curve, and compares with the standard feature curve point, judges whether this sensor performance is up to standard, and the output characteristic curve.
Said step 4) host computer serial ports links to each other through the MAX232 level transferring chip with singlechip controller AD μ C812; During system works; Matlab creates the serial equipment object through calling serial class and related function, and 10 data of sending of the real-time reception slave computer through the mode of interrupting.
After 10 data that said step 5) host computer will receive are carried out repeatedly fitting of a polynomial with least square method to sampled point, form the family curve of tested sensor.
Beneficial effect of the present invention is: high precision Resonator water level sensor performance detector of the present invention and method of testing; Used the microcontroller of high integration to control core as system; Have the advantages that cost performance is higher, stability is strong, precision is high; Actual motion is reliable, and good market application prospect is arranged.
Description of drawings
Fig. 1 is a high precision Resonator water level sensor performance detector hardware principle block diagram of the present invention;
Fig. 2 is high precision Resonator water level sensor performance detector middle water level sensor construction figure of the present invention;
Fig. 3 is a high precision Resonator water level sensor performance detector middle water level sensor equivalent circuit diagram of the present invention;
Fig. 4 is with precision frequency measurement method schematic diagram in the high precision Resonator water level sensor performance detector of the present invention;
Fig. 5 is a high precision Resonator water level sensor performance detector medium frequency Survey Software process flow diagram of the present invention;
Fig. 6 is sensor 1 characteristic test curve map in the high precision Resonator water level sensor performance detector of the present invention;
Fig. 7 is sensor 2 characteristic test curve maps in the high precision Resonator water level sensor performance detector of the present invention.
Embodiment
High precision Resonator water level sensor performance detector has adopted a kind of new type of frequency measuring method-same precision measuring method, and this makes that the sensor output frequency error that records is extremely low; Again the frequency utilization least square method of sampling is optimized processing on the other hand, makes the sensor characteristic curve that obtains approach true curve more.In addition, this tester has used the microcontroller of high integration to control core as system, and system reliability also is highly improved.This system has the advantages that cost performance is higher, stability is strong, precision is high, and actual motion is reliable, and good market application prospect is arranged.
Native system adopts the outstanding data acquisition chip AD μ C812 of a ten minutes of U.S. ADI company as system's microcontroller.AD μ C812 provides a cover complete system peripherals equipment, has not only saved to be the expense of system configuration additional devices, the more important thing is that this has improved the reliability of total system greatly.
In order to make test process convenient and efficient; Native system adopts air chamber pressure to change and simulates the actual water level variation; Promptly the air chamber pressure that inflation produces to sealed gas chamber is simulated the pressure that at the bottom of the casing water filling is to case, produces in the reality, and the change of tolerance is equal to the water tank SEA LEVEL VARIATIONS DURING in the air chamber.The system hardware theory diagram as shown in Figure 1; The system hardware circuit with single-chip microcomputer 4AD μ C812 as master controller; The main measurement that realizes air chamber pressure; Resonator water level sensor 2; Amplifying circuit 3 is passed through in the measurement of 6 output frequencies respectively; Amplification and rectification circuit 7 is to singlechip controller 4; Singlechip controller 4 output control signals are isolated through optocoupler 10; Output to 8 pairs of air inlet of air chamber of solenoid valve after amplifying through power amplification circuit 9 again and open and close and control, host computer PC 5 adopts powerful MATLAB instrument to realize and the communicating by letter of slave computer singlechip controller 4; The data of gathering are handled and to measuring the demonstration of curve.
The principle of work of Resonator water level sensor is that the variation of outside height of water level converts the variation of sensor internal diaphragm upward pressure to through air pressure, thereby causes the variation of sensor outputting inductance L.The level sensor structural drawing is illustrated in fig. 2 shown below, and comprises coil 11, iron core 12, air conduit 13, air cavity 14, film 15, spring 16.Shown in Resonator water level sensor equivalent electrical circuit Fig. 3, inductance L and capacitor C 1, C2 form resonant circuit, and are connected with digit reverse device TC4069UB, the outputting standard square wave, and along with the variation of water level, resonance frequency makes corresponding changes.
This test macro is set 10 measurement points altogether, in single-chip microcomputer, deposits 10 normal pressure values (corresponding one by one with the height of water level in the reality) in advance in, and the result measured and write down to single-chip microcomputer can to the output frequency of sensor at each normal pressure value point.
The native system workflow: the test beginning, controller 4 output signals are opened the air chamber switch and are begun air inlet, and system begins air chamber pressure simultaneously to be measured, and equates with the 1st force value of setting in advance up to recording force value, then stops air inlet; System begins frequency measurement, and will record frequency values and be saved in internal storage location, and the 1st point measurement finishes; Reopen the air inlet switch, begin the 2nd point measurement, finish up to setting 10 whole measurements by similar approach; 10 tests finish; Gained 10 dot frequency values are sent in the host computer 5 through serial ports successively, and host computer 5 utilizes the MATLAB instrument that these data are handled, the final sensor characteristic curve that draws; And with the standard feature curve point relatively, judge whether this sensor performance up to standard.
To level sensor frequency measurement and error analysis:
(1) with the precision measure ratio juris:
Frequency measurement is the core work of total system, and the height of the measuring accuracy of frequency will be directly connected to the accuracy of final response curved measurement.
The frequency measurement usual way mainly contains low frequency and surveys all high frequency frequency measurement methods, detects method frequently mutually.Low frequency is surveyed frequency error measurement very big problem in boundary's in all high frequency frequency measurement method existence, and the accuracy of measurement of frequency is difficult to bring up to certain one magnitude theoretically.
Detecting thought frequently mutually is exactly to detect the synchronization point between them through the phase coincidence point of catching between measured signal and the standard signal, and the switching that comes control counter with the phase coincidence point.The method can thoroughly eliminate in traditional frequency measuring method ± 1 counting error, but the very difficult seizure that is phase coincidence point of its shortcoming, this possibly cause measuring consuming time longer.
Native system adopts with precision frequency measurement method.Thought with precision frequency measurement method is or not actual gate time the value of fixing, but the integral multiple in measured signal cycle, and this makes signal strobe and measured signal synchronous, promptly has only when detecting the measured signal negative edge and arrive, and signal strobe is just opened.Therefore this method has been eliminated the measured signal counting has been produced ± 1 digital error, and has reached " same precision " measurement in whole measurement frequency range, and measuring accuracy improves greatly.Like Fig. 4 is with the precision measuring method schematic diagram.
The method realizes signal Synchronization with software, need use 1 timer and 2 counters.Before measuring measured signal is divided into two, an input port of guiding to external interrupt 0, another guides to the input port of counter 1.Timer 0 be provided with in advance one gate time T, counter 1 is used for measured signal is counted, counter 2 is used for reference clock signal is counted.
After measuring beginning, each timer of initialization and over interrupt 0.When the negative edge of measured signal arrives, produce and interrupt, the software starting gate is opened counter 1 sum counter 2 synchronously and is begun counting, and the pass is outside simultaneously interrupts 0.When timer 0 is timed to (preset gate time T to); Over interrupt 0; And this moment, external interrupt counter 1 sum counter 2 did not all stop counting, when the negative edge of measured signal arrives (this also can find out actual gate time T ' should be slightly larger than preset gate T).When the measured signal negative edge arrived, external interrupt 0 produces interrupted close synchronously counter 1 sum counter 2.In summary, the frequency of the signal can be expressed as:
,
is the measured signal frequency, M is the count value of the counter l, N 2 count value of the counter,
as a standard oscillator signal frequency (crystal frequency 11.0592MHZ).Fig. 5 is the frequency measurement software flow pattern.
(2) error analysis:
According to the measured signal frequency error propagation equation relative error:
.Where
for the oscillator frequency accuracy;
for the counter counting a relative error;
for the counter 2 counts relative error.
Since the measured signal is used as a trigger signal synchronization, the system error of the measured signal does not count, so
= 0.However, due to the crystal signal and strobe signals are not synchronized, so there
N = ± 1.
The value is generally much less than
, it can be ignored.So the same precision frequency measurement method may produce a relative error:
±
= ± 1 / N.And N is big more, and the relative error of the method is just more little.
In addition; This circuit is realized gate opening and is closed through the external interrupt service routine, so there is certain interrupt response time, so just increased error; Interrupt response generally needs 3 to 8 machine cycles, therefore can produce ± 5 interrupt response error.
Through the above error analysis, which shows that the maximum error of this method k '= (
N + (± 5)) / C '× 100%, where C' is the actual gate time T 'corresponding to the number of cycles of the reference clock signal.Since the actual gate time T 'should be slightly larger than the preset gates T, the gate with a preset time T corresponding to the number of cycles of the reference clock signal C should be slightly smaller than the C', it can have the maximum error can be approximated as k = (
N + (± 5)) / C
× 100%, we can see the actual error k 'approximation error is less than k.Timer is 16, and maximum count can reach 65536, but consider the problem of real-time, selects 0 time of timer can not be oversize, and promptly the initial value of timer 0 can not be too little.It is 30000 that native system is got the timer initial value, then can get maximum error k=(± 1+ (± 5))/(65536-30000) * 100%=0.0169%
Because the level sensor reference frequency output is about 20KHZ ~ 30KHZ, so can calculate, the system frequency measuring error has reached real high precision frequency measurement less than ± 5HZ.
The optimization process of sample frequency value and characteristic obtaining: native system adopts the matlab instrument as the host computer display interface, utilizes its powerful data processing function and graphical display function, makes the upper computer software design obtain to a certain extent simplifying.The host computer serial ports links to each other through the MAX232 level transferring chip with AD μ C812, and during system works, matlab creates the serial equipment object through calling serial class and related function, and 10 data of sending of the real-time reception slave computer through the mode of interrupting.10 data that host computer will receive are carried out match with least square method, form the family curve of tested sensor, and compare with standard feature curve tolerance range, and whether judge sensor performance up to standard.
Least square method (claiming least square method again) is a kind of mathematical optimization technology.It seeks the optimal function coupling of data through the quadratic sum of minimize error.Utilize least square method can try to achieve unknown data easily, and make the quadratic sum of error between data that these are tried to achieve and the real data, and finally can obtain matched curve for minimum.
Through theoretical derivation, can obtain the sensor output characteristic curve and can be similar to polynomial expression repeatedly and come match.Let the demand curve is
.The principle of least squares method is to make the following minimum values obtained when M is
,
value, so that M =
, where m is the sampling value (
,
) number.If M as
,
function, multi-function most value from the condition shows that these problems can find the following equations:
Solve problem.Can be obtained from the initial data:
,
,
,
and
value, and substituting into the above equation, you can find
,
value.
Above-mentioned course of solving questions can use the polyfit function to realize under the Matlab environment.Command format is:
P = polyfit (X, Y, n), where n represents the number of times to be fitted, X, Y sample values of m
,
the set of row vectors, wherein X, Y are 1
m row vector.Calculated result is [
] = P, P is 1
n row vector.
The system of 10 samples for each sensor group data, using four characteristic polynomial curve fitting of the sensor, i.e. n = 4, X is the value of the standard point level, Y is the next point of the standard water level sensor outputs a square wave frequency value, where X, Y are 1
10 row vector.
Like Fig. 6, two sensor characteristic curve test results shown in 7, to sample 10 times, corresponding actual conditions are every 5cm height once sampling.
Sensor 1 measurement data (unit: khz): 27.012,26.981,26.453,25.825,25.327,24.805,23.813,23.080,22.443,21.707,19.583
Sensor 2 measurement data (unit: khz):
28．103,27.944,27.352,26.828,26.324,25.805,25.410,24.082,23.643,22.304,21.58
Wherein up and down between two curves the zone be standard feature curve tolerance range, intermediate curve is tested sensor match family curve.
After using least square method that sampled point is carried out 4 order polynomial matches, obtain tested sensor characteristic curve.We can find out intuitively that sensor 1 performance test is qualified from above two figure, and sensor 2 side-play amounts are bigger, and test result is not up to standard.
A kind of novel Resonator water level sensor performance detector has thoroughly been eliminated the low stability of legacy test system, the shortcoming of hanging down precision, high level error.Native system has following several big innovation; At first, utilize a kind of novel high precision frequency measurement method, the system frequency measuring error is no more than ± 5HZ; This with traditional testing system easily the error of tens hertz even hundreds of hertz compare, system accuracy reaches a new level; Secondly, system carries out process of fitting treatment to the data of being sampled with least square method, has greatly optimized system's curve of output, make the sensor performance test curve more near with real curve; At last, adopted the high integration processor chips, system reliability also obviously improves.
Claims (5)
1. high precision Resonator water level sensor performance detector; It is characterized in that; Resonator water level sensor places in the sealed gas chamber that has the air inlet solenoid valve; The frequency that Resonator water level sensor output is measured arrives singlechip controller through amplifying circuit; Singlechip controller output control signal is through light-coupled isolation; Output to solenoid valve after amplifying through power amplification circuit again and air inlet of air chamber is opened and closed control, host computer adopts the communicating by letter of MATLAB tool implementation and slave computer singlechip controller, data processing and demonstration measurement result.
2. according to the said automobile radiators cooling air quantity of claim 1 on-line measurement device, it is characterized in that said singlechip controller adopts the data acquisition chip AD μ C812 of U.S. ADI company as controller.
3. the method for testing of a high precision Resonator water level sensor performance detector comprises high precision Resonator water level sensor performance detector, it is characterized in that, specifically comprises the steps:
1) test beginning; Singlechip controller output signal is through light-coupled isolation; Output to solenoid valve after amplifying through power amplification circuit again; Open air chamber and begin air inlet; System begins air chamber pressure simultaneously and measures; The 1st force value of in recording force value and singlechip controller, setting equates that singlechip controller outputs a control signal to solenoid valve, closes air chamber and stops air inlet;
2) single-chip controller receives the resonant level sensor, start frequency measurement, initialize the timer and open the external interrupt 0, when the falling edge of the signal arrives, an interrupt is generated, the software gate to be opened simultaneously open counter 1 and counter 2 starts counting and related external interrupt 0, when the timer 0 timed to when (ie preset gate time T), opening the external interrupt 0, and this time the external interrupt counter 1 and counter 2 not stop counting until the measured signal falling edge, when the falling edge of the signal, the external interrupt 0 interrupt is generated, the synchronization off counter 1 and counter 2, the measured frequency of the signal can be expressed as:
,
is the measured signal frequency , M l count value of the counter, N is the count value of the counter 2,
as a standard oscillator signal frequency;
3) will record the internal storage location that frequency values is saved in singlechip controller, the 1st point measurement finishes, repeating step 1) and 2) carry out 2 to 10 measurement;
4) 10 tests finish, and singlechip controller is successively sent in host computer through serial ports gained 10 dot frequency values;
5) host computer adopts the MATLAB instrument that frequency data are carried out the optimization process of sample frequency value, draws final Resonator water level sensor family curve, and compares with the standard feature curve point, judges whether this sensor performance is up to standard, and the output characteristic curve.
4. according to the method for testing of the said high precision Resonator water level sensor of claim 3 performance detector; It is characterized in that; Said step 4) host computer serial ports links to each other through the MAX232 level transferring chip with singlechip controller AD μ C812; During system works; Matlab creates the serial equipment object through calling serial class and related function, and 10 data of sending of the real-time reception slave computer through the mode of interrupting.
5. according to the method for testing of the said high precision Resonator water level sensor of claim 3 performance detector; It is characterized in that; After 10 data that said step 5) host computer will receive are carried out repeatedly fitting of a polynomial with least square method to sampled point, form the family curve of tested sensor.
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| CN107783561A (en) * | 2017-09-19 | 2018-03-09 | 嘉兴学院 | Level sensor bolt initial position automatic adjustment system |
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| CN109186720A (en) * | 2018-09-08 | 2019-01-11 | 芜湖乐佳电器有限公司 | A kind of water level sensor durability test method |
| CN109806490A (en) * | 2019-01-28 | 2019-05-28 | 吉林大学第一医院 | A kind of intelligent medical genitalia nursing disinfection control system and method |
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| CN111551231A (en) * | 2020-03-27 | 2020-08-18 | 西京学院 | Water level detection device |
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| CN112945349A (en) * | 2021-02-03 | 2021-06-11 | 浙江厚德气动元件有限公司 | Pneumatic triple piece of automatic drainage of real-time supervision water level |
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