CN1174224C - Liquid level measuring instrument and its error compensation method - Google Patents
Liquid level measuring instrument and its error compensation method Download PDFInfo
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- CN1174224C CN1174224C CNB991172833A CN99117283A CN1174224C CN 1174224 C CN1174224 C CN 1174224C CN B991172833 A CNB991172833 A CN B991172833A CN 99117283 A CN99117283 A CN 99117283A CN 1174224 C CN1174224 C CN 1174224C
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Abstract
The present invention relates to a liquid level measuring instrument and an error compensation method thereof. A pressure sensing transmitter, a temperature sensing transmitter, a power supply, a machine box, press keys, an LED display device and a circuit board are installed together and connected by respectively corresponding electric cable signal wires and power supply wires to form the measuring instrument. Circuits of the pressure transmitter and the temperature transmitter, multi-path analogue switches, an A/D converter, a single chip microprocessor, a data and program storage device, a serial interface, a keyboard/display interface and an LED display device are connected together by respectively corresponding signal wires to form a circuit. The error compensation method has the scheme that firstly, signal data outputted by the pressure transmitter and the temperature transmitter is measured; subsequently, the non-linear error, the temperature error and the zero drift error of a pressure signal are compensated by the designed control compensation software program of the single chip microcomputer. The measuring instrument of the present invention has the advantages of high precision, high stability and reasonable price. The price of the present invention is approximate 1/10 of the price of the foreign similar products.
Description
The present invention is a kind of fluid level measuring instrument and error compensating method thereof, belongs to the automatic measurement instrumental technique.
In commercial measurement, instrument and meter for automation field of measuring technique, the instrument consumption maximum of ergometry.And the dynamometry instrument is divided into the liquid level instrument of gaging pressure and measurement liquid levels height, and the measurement of liquid level is commonplace, and application is also relatively wider.For example: the measurement of tap water water level and control, when water level was lower than the regulation lower limit, the output control signal made water pump to start and draws water that when water level was higher than higher limit, water pump promptly stopped pumping; The oil level in oil field needs to measure, and the liquid level that holds oil sump needs to measure, so that know the physical location of pasta; The oil-level measurement of storage tank, the height of a large-scale storage tank are 25 meters, and the weight and volume of the oil of injection and discharge can just can calculate by measuring its oil level surface.The sensor of measuring liquid level and the pressure-sensing device of transmitter mainly are the diffused-silicon pressure chips.The at present external survey liquid level instrument and the technical merit of sensor are than higher, stability is also fairly good, for example the precision of ST3000 type pressure (liquid level) transmitter of HONIWELL company is about 0.1～0.2%, maintain the leading position in the international market, still the price of a this fluid level measuring instrument is about 70,000 yuans.This price is beyond affordability for the users of China.Therefore, the survey liquid instrument and the sensor of the suitable China of research manufacturing actual conditions are very necessary.Want to improve the measuring accuracy of measurement instrument and sensor, only depending on the performance that improves the diffused-silicon pressure chip is the comparison difficulty, for example: the diffused-silicon pressure chip of NOVA company, its temperature, non-linear and reproducibility error be ± and 0.2～0.5%, converting its precision at last is ± 0.5～1.0%.The technical feature of the diffused-silicon pressure chip of China's manufacturer production a little less than external product, could improve precision even use the chip of offshore company also will compensate.The error compensating method of pressure sensing measurement instrument has a variety of, topmost method has three kinds: first kind is compensating-pressure transducer, make that the straight line of the straight line of Control current and temperature variation and pressure transducer and temperature variation is identical, promptly pass through the compensating for variations temperature error of electric current, this method can only the compensation temperature error, but can not the compensating non-linear error; Second kind is the compensatory pressure variator, utilize operational amplifier design current transmitter circuit, add a sampling resistor at circuit output end, and the voltage signal at resistance two ends is fed back to amplifier input terminal, form negative feedback, widespread usage in the producer of the nonlinearity erron that compensation produces when increasing owing to output current, this method some production pressure transducers at home; The third is the single chip microcomputer by measurement instrument, in the two dimensional surface of pressure unit and temperature, sets up the linear relationship of the two, by software program compensation temperature error, and the nonlinearity erron of while compensatory pressure signal; The 4th kind is to utilize surface fitting method, but the toroidal function that wants to set up temperature, pressure measuring value and standard output numerical value is the comparison difficulty, both needed a large amount of computer program computings, obtain the coefficient of toroidal function, also to carry out measurement repeatedly, if measurement data is how to a certain degree, so during design factor, oscillatory occurences be can occur, permissible accuracy and coefficient that can not ask function do not reached on the contrary.Present this method is just inquired into the stage in theory, can't carry out practical application, and its advantage is that compensation precision is than higher.Utilize microcomputer that signal of sensor is compensated, can reach the purpose that improves the measuring instrument precision fully, can save the cost of measurement instrument and sensor again.
Though purpose of the present invention is exactly to have external measuring instrument precision height now in order to overcome and to solve, but expensive, the user is difficult to accept, domestic fluid level measuring instrument then precision is lower, less stable, the also still higher and compensating-pressure transducer of price can only the compensation temperature error, can not the compensating non-linear error or the surface fitting compensation method complicated again, easily vibration, the shortcoming of impracticable grade and problem, the research invention is a kind of by utilizing single chip microcomputer that the output signal of pressure unit is compensated, and reaches compensation temperature, non-linear and reproducibility error, so that the precision height to be provided, good stability, price is more reasonable, only be about 1/10 of external like product price, fluid level measuring instrument that the user is easy to accept and error compensating method thereof.
The present invention realizes by following technical proposals: the contour structures synoptic diagram of high-precision liquid level measurer as shown in Figure 1, its circuit block diagram is as shown in Figure 2.It is by pressure transducer and pressure unit 1, temperature sensor and temperature transmitter 2, power supply 3, cabinet 4, button 5, light-emitting diode display, circuit board connects and composes jointly, its mutual alignment and annexation are: pressure transducer and pressure unit 1, temperature sensor and temperature transmitter 2 are electrically connected with cabinet 4 interior related circuit plates mutually by shielded cable respectively, power supply 3 is electrically connected mutually by the power end of power supply output line with cabinet 4 interior related circuit plates, comprise the upper limit, lower limit, report to the police, density, compensation, zero point, numeral (0～9), move to right, panel and cabinet 4 that affirmation waits 5 figure place sign indicating number display screens 6 of button 5 and light-emitting diode display to constitute are fixedly connected, button 5 respectively with cabinet 4 in corresponding keyboard/display interface circuit be electrically connected mutually, LED display 6 is loaded on the panel left side and is electrically connected mutually with the keyboard/display interface circuit of cabinet 4 interior circuit boards; Its circuit is by the pressure to current transmitter circuit, the current/voltage-converted multi-channel analog switch circuit, the temperature current transmitter circuit, the A/D converter circuit, the single chip microcomputer circuit, data memory, serial interface circuit, memory under program, keyboard/display interface circuit, light-emitting diode display is electrically connected formation jointly, and its interconnected relationship is: the pressure to current transmitter circuit is respectively by the pressure transducer output signal line, pressure to current transmitter output signal line, power lead respectively with pressure transducer 1, the current/voltage-converted multi-channel analog switch circuit, power supply is electrically connected mutually; The temperature current transmitter circuit is electrically connected the A/D converter circuit mutually with temperature sensor 2, current/voltage-converted multi-channel analog switch circuit, power supply respectively by temperature sensor output signal line, temperature current transmitter output signal line, power lead respectively and is electrically connected mutually with current/voltage-converted multi-channel analog switch circuit, single chip microcomputer circuit respectively by switching signal output line, the A/D converter output line of current/voltage-converted multiway analog switch respectively; The single chip microcomputer circuit is electrically connected with data-carrier store, program storage, keyboard/display interface circuit respectively mutually by the data-signal output line in the microcomputer bus, program singal output line, keyboard signal incoming line and shows signal output line respectively; Data-carrier store is electrically connected with serial interface circuit mutually by the data storage output signal line; Keyboard/display interface circuit is electrically connected with control key board, light-emitting diode display respectively mutually by keyboard signal output line, LED shows signal output line respectively.Its circuit theory diagrams such as Fig. 3～shown in Figure 6, wherein: pressure to current transmitter circuit schematic diagram as shown in Figure 3, it is electrically connected jointly by current transducer IC19, diode D6, socket S11, potentiometer W2～W4, resistance R 12～R13, capacitor C 45, C46 and constitutes; Temperature current transmitter circuit schematic diagram as shown in Figure 4, it is electrically connected jointly by temperature current transmitter IC 20, triode Q2, diode D7, socket S12, standard platinum resistance PT100, resistance R 14～R17, capacitor C 47～C49 and constitutes; The circuit theory diagrams of voltage-stabilized power supply circuit, A/D converter circuit and current/voltage-converted multi-channel analog switch circuit as shown in Figure 5, wherein: analog power AVDD is electrically connected jointly and is constituted by voltage stabilizer integration member IC4, capacitor C 15, C16, pressure limiting diode D1; Analog power AVSS is electrically connected jointly and is constituted by voltage stabilizer integration member IC5, capacitor C 17, C18, pressure limiting diode D2; Digital power DVDD is electrically connected jointly and is constituted by voltage stabilizer integration member IC6, capacitor C 19, C20, pressure limiting diode D3; Digital power DVSS is electrically connected jointly and is constituted by voltage stabilizer integration member IC7, capacitor C 21, C22, pressure limiting diode D4; Probe power DVSS is electrically connected jointly and is constituted by voltage stabilizer integration member IC8, capacitor C 23, C24, pressure limiting diode D5; The A/D converter circuit is electrically connected jointly and is constituted by A/D converter integration member IC1, voltage stabilizer integration member IC3, crystal oscillator crystal CZ, capacitor C 1～C14, resistance R 1～R4; The current/voltage-converted multi-channel analog switch circuit is electrically connected jointly by multiway analog switch device IC2, resistance R 5～R8, capacitor C 23～C28 and constitutes; The circuit theory diagrams of single chip microcomputer circuit and data-carrier store, program storage, keyboard/display interface circuit as shown in Figure 6, wherein: the single chip microcomputer circuit is electrically connected jointly and is constituted by single chip microcomputer IC13, crystal oscillator crystal MZ, capacitor C 31～C33, resistance R 9, address latch IC10, interface lock storage IC14 Sheffer stroke gate IC15; Data memory is memory integration member IC12; Memory under program is that memory integration member IC11, keyboard/display interface circuit are electrically connected jointly and are constituted by keyboard/display interface integration member IC16, code translator integration member IC17; Serial interface circuit is that RS-232 interface IC circuit 18 constitutes; Buzzer circuit is electrically connected jointly by hummer TON, triode Q1, resistance R 10 and constitutes.
The error compensating method of fluid level measuring instrument of the present invention is: the output signal data of first gaging pressure exactly and temperature transmitter, design the assemble software program of a cover single chip microcomputer again, record in the program storage of instrument program is defeated, when the fluid level measuring instrument operate as normal, adopt the pressure signal compensation program, by calculating and handle measurement data, the error that the nonlinearity erron of compensatory pressure signal, temperature error and zero point produce with temperature drift; After every sensor and transmitter insert fluid level measuring instrument, at first carry out normal data and measure, be input in the measuring instrument by keyboard again and deposit in the data-carrier store that power down do not lose; " compensation " button of this fluid level measuring instrument is that the setting measurement data are through over-compensation or without the function key that compensates, when the measurement standard data, be set to not be with compensate function, when normal surveying work, then be set to be with compensate function, pressure, temperature data are controlled and gathered to single chip microcomputer periodically by the output terminal of interface; After gathering one group of pressure on the number signal earlier, gather one group of temperature digital signal again, utilize temperature signal that pressure signal is carried out zero point and span compensation, the data after the compensation are sent display to show and can be exported by serial line interface; Its normal data measuring principle figure as shown in Figure 7, pressure transducer and transmitter 17 are connected electrically to measurement instrument 12 by going between, temperature sensor and transmitter 28 are connected electrically to measurement instrument 12 by going between.Temperature constant temperature control box 9 has temperature control-20～+ 50 ℃ scope, can regulate temperature, and have the steady temperature function, and above the standard piston pressure gauge 10 standard weights 11, connecting pipe 13 arrives pressure transducer 1 with the pressure of piston manometer 10 by the liquid conductive in the pipe.Pressure unit 1 and temperature transmitter 2 are placed in the constant temperature oven 9, Temperature numerical Ti (i=0～6) is set, i measures temperature spot, can select i be spaced apart+10 ℃ or+15 ℃, but the temperature interval is more little, its compensation precision is just high more; Observe the measurement data of temperature transmitter through longer a period of time, make range of temperature reach desired precision, for example: Ti ± 0.01 ℃, and all stable in 10 minutes internal pressures and temperature data, then think to have reached the constant temperature requirement, can measure one group of data V
(0, j)(j=0～10, j is the numerical value of standard test weight); At first measure zero point, counterweight is zero, measurement data V
(0,0)Add counterweight P1, measurement data V
(0,1), add counterweight P1+P2, measurement data V
(0,2), add counterweight P1+P2+P3, measurement data V
(0,3)Add counterweight P1+P2+P3+P4, measurement data V
(0,4)Add counterweight P1+P2+P3+P4+P5, measurement data V
(0,5)Measurement data V
(i, j)The numerical value that how much depends on standard test weight of middle j, or the interval of selection pressure select j=0～6 usually; Regulate temperature T 1 again, utilize same procedure to measure second group of data, measurement data V by that analogy
(i, j), (i=0～5, i=0～6); Wherein pressure measurement data has seven groups of data, because the output numerical value that P0 is a pressure when being zero, is 4mA corresponding to the output current of transmitter; Because pressure transducer and pressure unit have its property, promptly in its output performance difference of different temperature provinces, and diversity ratio is bigger.Fig. 8 be the fluid level measuring instrument pressure unit behind temperature T, pressure compensation output Pout and the curved surface figure in the three dimensions formed of measured value Px, the curved surface figure that output behind figure mean camber " A ", " B ", " C ", " D ", " E ", " F ", the pressure compensation when being different temperatures and measured value are formed, wherein temperature T
A＜T
B＜T
C＜T
D＜T
E＜T
FThe present invention has adopted the method for dividing section, subregion to carry out nonlinear compensation, and the performance of pressure output does not have a too big variation in smaller zone, compensation precision height like this, and method is simple again.
The simple style of work principle of this fluid level measuring instrument is as follows: " upper limit " connects the maximum measuring height that key is a measurement instrument, prescribes a time limit greater than last when the actual measurement height, has hummer TON to report to the police." lower limit " button is the minimum measuring height of measurement instrument, when actual measurement highly is lower than down in limited time, has hummer TON to report to the police.Utilize " warning " button can cancel warning, the main effect of warning is to understand timely and handle level condition." density " button is that measured density of liquid is set, so that calculate height by pressure gauge." compensation " button be the setting measurement data through over-compensation or without compensation, promptly during the measurement standard data, be set to not be with compensate function, when normal the measurement, to be set to be with compensate function." zero point " button is that be set the migration zero point that sensor is placed on least significant end and actual zero elevation in the liquid." affirmation " button is that function is determined or the return measurement state.Next row of panel is a digital keys:
With
Pressure transducer is connected to the pressure to current transmitter, and 4～20mA current signal of output produces voltage VP through sampling resistor R7, has promptly realized current/voltage-converted; Temperature sensor is connected to temperature transmitter, and 4～20mA current signal of output produces voltage VT through sampling resistor R8, has promptly realized current/voltage-converted; Controlled by single chip microprocessor multiway analog switch IC2, wherein DA0, DA1, DA2 control signal end, time grate VP and VT, through the input end VIN of analog switch output voltage signal to A/D converter, pressure, temperature data are controlled and gathered to single chip microcomputer periodically by the DA0～DA7 output terminal of interface.At first gather after one group of pressure on the number signal, gather one group of temperature digital signal again, utilize temperature signal that pressure signal is carried out zero point and span compensation.Data after the compensation send light-emitting diode display to show, and can export by serial line interface; Button on the front panel is connected to the keypad/display interface circuit.When pressing keys, the keypad/display interface circuit just will deposit in wherein by bond parameter at that time, and, just remove the state of this button after the single chip microcomputer response by of higher level's single chip microcomputer application interruption of IRQ leads ends to it, promptly finished the control procedure of a pressing keys.Can revise normal data by keyboard, some functional parameters of instrument also can be set.After every sensor inserts instrument, at first will carry out canonical measure, the data that record are normal data, are input to instrument and deposit in the data-carrier store by keyboard, this storer has the characteristic that power down is not lost, and all will utilize this group normal data when single chip microcomputer compensates at every turn; The action principle of its circuit is as follows: the circuit of diffused silicon pressure transmitter as shown in Figure 3.SENSON is a pressure transducer.IC19 is a current transducer.Voltage 24V enters IC19 through polarity restriction diode D101, and potentiometer W2 is that electric current equals 4mA when regulating zero pressure.Resistance R 12 and potentiometer W3 are gain adjusting circuits, and promptly during full scale pressure, electric current equals 20mA.Resistance R 13 is current-limiting resistances of zero point and gain adjusting circuit.Potentiometer W4 is the Control current of regulating pressure transducer, and the output voltage of the Pin1 of IC19 is 75mV, and the electric current by pressure transducer SENSOR is I
p=75mv/R
W4Capacitor C 45 and C46 are filter capacitors.The circuit of temperature transmitter as shown in Figure 4.IC20 is a temperature transmitter, and diode D7, capacitor C 48 and capacitor C 49 are formed limiting filter circuit.Triode Q2 plays the Current Regulation effect.Resistance R 14, R15, R16 and R17 are the measurement temperature ranges of control transmitter, and mutual relationship wherein and numerical value are searched definite in the device handbook.Map parameter is-100～+ 100 measurement temperature ranges.PT100 is the PT100 standard platinum resistance; The A/D change-over circuit as shown in Figure 5.Stabilized voltage supply device IC4, capacitor C 15, C16 and pressure limiting diode D1 have constituted analog power AVDD.Stabilized voltage supply device IC5, capacitor C 17, C18 and pressure limiting diode D2 have constituted analog power AVSS.Stabilized voltage supply device IC6, capacitor C 19, C20 and pressure limiting diode D3 have constituted digital power DVDD.Stabilized voltage supply device IC7, capacitor C 21, C22 and pressure limiting diode D4 have constituted digital power DVSS.Stabilized voltage supply device IC8, capacitor C 23, C24 and pressure limiting diode D5 have constituted probe power DVSS.A/D converter device IC1, voltage-stabilizing device IC3, crystal CZ, capacitor C 1～C4 and resistance R 1～R4 constitute the A/D converter circuit.Multiway analog switch IC2, resistance R 5, R6, R7, R8 and capacitor C 23～28 constitute analog switching circuit, and wherein R7, R8 are respectively the sampling resistors of pressure and temperature electric current; The single chip microcomputer circuit as shown in Figure 6.IC13 is a single chip microcomputer, and crystal MZ and capacitor C 31, C32 constitute crystal oscillating circuit.Capacitor C 33 and resistance R 9 constitute reset circuit.IC12 is a data-carrier store, is used for the measuring memory normal data, has power down and does not lose characteristic.IC11 is a program storage, stores single chip microcomputer program.IC10 is the low eight bit address latchs of single-chip microcomputer.IC14 is the interface lock storage, and output DA0～2 are used for controlling the A/D converter circuit, gating pressure signal VP or temperature signal VT; Output terminals A P14 is used for controlling hummer TON, if warning is arranged, then AP14 is a high level, otherwise is low level.Hummer TON, resistance R 10 and triode Q1 form buzzer circuit.IC16 is keyboard/display interface circuit, forms scan interface with three-eight code translator IC17, and keyboard is scanned, and is connected to light-emitting diode display by S6, and S10 is a keyboard socket, is connected to the keyboard on the instrument face plate.Serial RS-232 interface device IC18 and C40～C44 forms serial line interface, and capacitor C 34～C38 is the filter capacitor of microcomputer circuit part.
The collection of its single chip microcomputer and Control Software program are as follows: this measuring instrument main program flow block scheme as shown in Figure 9.After replying the position by cable, to keyboard/display interface circuit IC16 initialization, it is N key scanning mode that keyboard is set, and determines LED scanning figure place.The signal of collecting temperature, the numerical value of at every turn sampling is replaced previous temperature value.The sampling time of pressure signal is about 3～5 times/second, comes compensate for height H by temperature signal.Interruption T0 is set determines that serial RS232 communication baud rate is 1200.Interrupt INT 1 is that keyboard response interrupts.After elder generation's once sampling temperature initial value, enter main circulating program again, multiway analog switch selects pressure channel, gathers pressure signal P
X, carry out the pressure signal performance compensation.Open interrupt INT 1, judged whether keyboard interrupt? there is keypad function to handle.Return master routine and carry out major cycle; Serial communication programmer: the serial communication programmer flow diagram as shown in figure 10.When serial communication programmer is arrived in program run, utilize ASCII character, send with 1200 baud rates.Send height H+measuring height value, transmit temperature T+measurement temperature value, delivery quality W+ oil tank mass value; The keyboard interrupt program: keyboard interrupt program circuit block scheme as shown in figure 11.After master routine was with measurement data demonstration and communication, the key point dish interrupted, and no responder returns.Have and interrupt entering the keyboard handling procedure, judge whether to be keyboard setting " compensation " parameter function? be to continue to enter the change of each parameter and check state.Not, continue to be judged as " upper limit ", " lower limit " setting? be to enter change and check state.Not, continue to be judged as " mode " and be provided with? be to enter the state of setting.Judge and enter other functions.Setting is finished and is returned; The pressure signal compensation program: pressure signal compensation program flow diagram as shown in figure 12.After master routine sampled pressure signal enters compensation program, in the curved surface of temperature, pressure and compensatory pressure, utilize the once linear funtcional relationship of two dimensional surface, to the temperature error of pressure nonlinearity erron, pressure and zero point the error with temperature drift compensate; Design temperature Ti, (i=0～5), temperature interval are+10 ℃, from-10～+ 40 ℃, measurement data is V
(i, j), (i=0～5, j=0～6), just six temperature spots obtain 6 groups of measurement data altogether, 7 of every group of data, wherein T
0＜T
1＜T
2＜T
3＜T
4＜T
5: P0＜P1＜P2＜P3＜P4＜P5＜P6; At first, judge the zone at temperature signal Ti place: between T0＜Tx＜T1 ℃, perhaps between T1＜Tx＜T2 ℃, perhaps between T2＜Tx＜T3 ℃, perhaps between T3＜Tx＜T4 ℃, perhaps between T4＜Tx＜T5 ℃, when Tx＜T0, press between T0＜Tx＜T1 ℃ and calculate; When Tx＞T5, press between T4＜Tx＜T5 ℃ and calculate; The temperature range of determining temperature T x is T
(i, i+1)Continue to judge the temperature spot at Tx place afterwards, when Tx＜Ti+Ti/2, the normal data of compensation is selected one group of data V of Ti temperature spot
(i, j), (j=0～6); When Tx＞Ti+Ti/2, the normal data of compensation is selected one group of data V of Ti+1 temperature spot
(i+1, j), (j=0～6); Pass through temperature T
X, calculate the value of Δ T:
ΔT＝T
X-T
25 (1)
T25 is temperature T=25 ℃, is the industrial standard Temperature numerical, the numerical value when the liquid level numerical value that is to say the pressure that calculates at last or measurement should be 25 ℃; Determine temperature T
XBehind the temperature spot at place, continue to judge the section at pressure P X place again, first section: P
0＜P
X＜P
1, second section: P
1＜P
X＜P
2, the 3rd section: P
2＜P
X＜P
3, the 4th section: P
3＜P
X＜P
4, the 5th section: P
4＜P
X＜P
5, the 6th section: P
5＜P
X＜P
6, work as P
X＜P
0The time, press P
0＜P
X＜P
1Calculate, work as P
X＞P
6The time, press P
5＜P
X＜P
6Calculate, determined T
XTemperature is in i temperature spot and pressure P
XAt P
jAnd P
J+1Section, i.e. P
(i, j)And P
(i, j+1), in this section, utilize linear interpolation method to calculate actual pressure numerical value then;
Section normal pressure difference is got in calculating:
ΔPn＝P
(i，j+1)-P
(i，j) (2)
Section calibrated altitude difference is got in calculating:
ΔHn＝H
(i，j+1)-H
(i，j) (3)
Calculate corresponding force value in the time of 25 ℃:
P
out＝Pnx×(1+α)+P
25(i，j) (4)
Wherein, Pnx={ (P
N (i, j+1)-P
N (i, j))/(P
(i, j+1)-P
(i, j)) * P
X+ P
(i, j)
α＝{(P
(i，j)-P
25(i，j))/(P
X-P
25)}
---P
N (i, j)It is normal pressure;
---P
25 (i, j)Pressure value when being 25 ℃;
Calculate corresponding height value in the time of 25 ℃;
H
n25＝H
(i，j)+(ΔHn/ΔPn)×(P
out-P
25(i，j))?(5)
Formula (4) is the pressure value after over-compensation; Formula (5) is the height number after over-compensation.
Utilize error compensating method of the present invention, through design compensation pressure unit and fluid level measuring instrument, prove that this theoretical method is feasible, practical application is fairly simple, compensation effect is relatively good, the pressure unit that produces and the performance of measurement instrument is more stable, precision is high can reach compensation effect fully.Both compensated the nonlinearity erron of temperature error and pressure, solved better also that maximum difficult point---zero point is with the error compensation of temperature drift.
The present invention compares following advantage and beneficial effect with existing fluid level measuring instrument: (1) compensates by the output signal of the single chip microcomputer in the secondary instrument to pressure unit, reach the purpose of compensation temperature and nonlinearity erron, make that like this price comparison of this fluid level measuring instrument and transmitter is reasonable, be about 1/10 of external like product price, be fit to the present actual conditions of China, be easy to be accepted, be easy to apply by the user; (2) select 22 AD7703 type A/D converters for use, the advanced ∑ of this devices use-Δ technology, the conversion accuracy height, temperature error is little, good stability; (3) to diffused silicon pressure transmitter main error---the temperature drift error at zero point, the temperature error of range, non-line error compensate, and this accuracy of instrument after the compensation is: ± 0.1～0.2%/FS, improved the precision of measuring instrument greatly; (4) this measuring instrument measuring height resolution is 1mm; Temperature resolution is 0.1 ℃; (5) this measuring instrument mode that software engineering and hardware circuit combine is compared with other measuring instrument, has increased the transmitter of measuring temperature; Utilize assembly language to design the compensation method of segmentation surface fitting; (6) to compare with the common survey instrument be to have increased by one group of temperature transmitter to this measuring instrument, increased by the temperature signal of 4～20mA again aspect circuit, is used for the temperature error of compensatory pressure signal; (7) after the temperature and pressure transmitter was connected to this measuring instrument, by measuring its " normal data " and utilizing keyboard that normal data is deposited in this measuring instrument, measurement instrument compensated gaging pressure numerical value automatically by software program, has promptly finished compensation.Avoid utilizing other hardware compensating method, needed the loaded down with trivial details work of repeated measurement compensation; (8) in the curved surface of temperature, pressure measuring value and compensation output numerical value, adopt the temperature and pressure measured value to carry out the two-dimensional linear compensation method of two-dimensional linear compensation method, pressure survey numerical value and pressure compensation numerical value.So just avoided setting up the computation process of the complexity of toroidal function, the method simple possible; (9) the present invention is placed on (as constant temperature oven) in the identical temperature environment with pressure unit and temperature transmitter, behind the temperature constant temperature numerical value, measures Temperature numerical, zero pressure numerical value in gaging pressure transmitter 4～20mA scope and the pressure value in the range ability; Behind the transformation temperature numerical value, constant temperature measurement temperature and pressure numerical value carries out constant temperature measurement in whole temperature range again, has just finished raw data acquisition.
Below Figure of description is further specified as follows: Fig. 1 is the contour structures synoptic diagram of this high-precision liquid level measurer; Fig. 2 is its circuit structure block scheme; Fig. 3～Fig. 6 is its circuit theory diagrams, and wherein, Fig. 3 is its pressure to current transmitter circuit schematic diagram; Fig. 4 is its temperature current transmitter circuit schematic diagram; Fig. 5 is its voltage-stabilized power supply circuit, A/D converter circuit and current/voltage-converted multi-channel analog switch circuit schematic diagram; Fig. 6 is the circuit theory diagrams of single chip microcomputer circuit, data memory, memory under program, keypad/display interface circuit; Fig. 7 is normal data measuring principle figure; Fig. 8 is the curved surface figure in the three dimensions formed of output Pout behind temperature T, the pressure compensation and measured value Px; Fig. 9 is this measuring instrument master routine block scheme; Figure 10 is this measuring instrument serial communication programmer flow diagram; Figure 11 is this measuring instrument keyboard interrupt program circuit block scheme; Figure 12 is this measuring instrument pressure signal compensation program flow diagram.In each circuit diagram, all identical sign end points are electrically connected mutually, and socket S3 and S11 are electrically connected mutually, and socket S4 and S12 are electrically connected mutually, and socket S2 and S5 are electrically connected mutually.
Embodiments of the present invention can be as follows: (1) presses Fig. 3～shown in Figure 6, and draw PCB is screened components and parts then and installed and connect debugging.Wherein: the optional AD7703 type of IC1 A/D converter; The optional A/D7501 type of IC2 multiway analog switch; The accurate stabilized voltage supply of the optional A/D580 type of IC3; The optional HM7805 type of IC4, IC6 stabilized voltage supply; The optional HM7905 type of IC5, IC7 stabilized voltage supply; The optional AM7824 type of IC8 stabilized voltage supply; The optional 74LS373 type of IC10, IC14 latch; The optional AM2764 type of IC11 memory under program; The optional AM2816 type of IC12 data memory; The optional INTEL8031 type of IC13 single chip microcomputer, the optional HD74LS00 type of IC15 rejection gate; The optional INTEL8279 type of IC16 keyboard/display interface circuit; The optional HD74LS138 type of IC17 code translator; The optional TS232 serial interface circuit of IC18, the optional AD693 type of IC19 current transducer; The optional XTR103 type of IC20 current transducer; The optional NT830 type of pressure transducer (SENSOR); The optional PT100 type platinum resistance of temperature sensor (measurement temperature thermistor); The optional 1N4001 type of triode Q1, Q2; The optional 6MHz crystal of crystal oscillator crystal CZ; The optional 3.579MHz crystal of MZ; (2) press Fig. 1, design shown in Figure 2 and, install and be electrically connected by the described annexation of top instructions then with machine-tooled method processing cabinet and panel; Operate by Fig. 7～measurement standard data shown in Figure 8 and by the described error compensating method of top instructions again, press Fig. 9～shown in Figure 12 and top described software program of instructions again, work out the microcomputer collection and the Control Software program of this measuring instrument---comprise this measuring instrument master routine, serial communication programmer, keyboard interrupt program, pressure signal compensation program, and operate by the described style of work principle of top instructions, just can implement the present invention preferably.
Claims (2)
1. the error compensating method of a fluid level measuring instrument is characterized in that, it comprises the steps:
First step normal data is measured
Pressure unit and temperature transmitter are placed in the constant temperature oven, Temperature numerical T is set
i, i measures temperature spot, and same measurement temperature spot is measured one group of normal pressure data V under constant temperature
(0, j), j is the interval of selection pressure; Regulate temperature T again
i, utilize same procedure to measure temperature spot gaging pressure data V successively at other
(i, j)
Second step was set up the error compensation function
By measuring the subregional mode of temperature, toroidal function between pressure signal and temperature, gaging pressure and the compensatory pressure is concerned the two dimensional surface once linear funtcional relationship that is summed up as pressure and compensatory pressure, sets up 3 corresponding once linear penalty functions respectively as follows:
1. pressure limit is divided into a plurality of sections, sets up a pressure linear function: at temperature range T
iTo T
I+1In, pressure and compensatory pressure are the two dimensional surface once linear relationships, at pressure V
0To V
jIn the scope, again with pressure V
jTo V
J+1Be defined as pressure nonlinear compensation section, utilize pressure V
jTo V
J+1, V
jNormal pressure P with correspondence
jTo P
J+1, P
jBuild-up pressure linear compensation linear function P as follows
Nx(V):
P
nx(V)＝{(P
n(i，j+1)-P
n(i，j))/(P
(i，j+1)-P
n(i，j))}×P
x+P
(i，j) (1)
Wherein, P
N (i, j)Be normal pressure, P
(i, j)Be pressure when the i temperature; P
xBe measured pressure;
2. temperature is divided into a plurality of zones, the linear function of pressure when set up measuring temperature: when the measurement temperature is T with 25 ℃
xAnd pressure P
xThe time, utilize temperature T
xTo 25 ℃ and pressure P
xTo P
25The temperature compensation linear function P of pressure when setting up 25 ℃
Out(T):
P
out(T)＝P
nx×(1+α)+P
25(i，j) (2)
Wherein, α=(P
(i, j)-P
25 (i, j))/(P
x-P
25); P
25 (i, j)Pressure value when being 25 ℃;
3. set up the linear penalty function of liquid level and pressure: when temperature is 25 ℃, utilize liquid level H
(i, j), H
N25And pressure P
Out, P
25Set up Liquid level compensator linear function H
N25(P):
H
n25(P)＝H
(i，j)+(ΔHn/ΔPn)×(P
out-P
25(i，j)) (3)
Wherein, section normal pressure difference: Δ Pn=P
(i, j+1)-P
(i, j), section calibrated altitude difference: Δ Hn=H
(i, j+1)-H
(i, j)H (i, level gauging height when j) being point for measuring temperature i, pressure section j;
The 3rd step error compensation
Judge earlier and measure temperature T
xThe zone at place, and the section at definite pressure V place are then at V
jTo V
J+1The interval in, utilize the linear compensated linear function of the pressure P of formula (1)
Nx(V) calculate pressure compensation numerical value P
NxAccounting temperature T then
x-25 ℃ difference, the temperature compensation linear function P of pressure when utilizing 25 ℃ of formula (2)
Out(T) calculate pressure P
OutUtilize the Liquid level compensator linear function H of formula (3) at last
N25(P) the liquid level H of calculating after compensation
N25
2. fluid level measuring instrument of implementing the described method of claim 1, it is characterized in that, it is by pressure transducer and pressure unit (1), temperature sensor and temperature transmitter (2), power supply (3), cabinet (4), button (5), light-emitting diode display, circuit board connects and composes jointly, its mutual alignment and annexation are: pressure transducer and pressure unit (1), temperature sensor and temperature transmitter (2) are electrically connected with the interior related circuit plate of cabinet (4) mutually by shielded cable respectively, power supply (3) is electrically connected mutually by the power end of power supply output line with the interior related circuit plate of cabinet (4), comprise the upper limit, lower limit, report to the police, density, compensation, zero point, numerical key 0 to 9, move to right, panel and cabinet (4) that 5 figure place sign indicating number display screens (6) of button of acknowledgement key (5) and light-emitting diode display constitute are fixedly connected, button (5) respectively with cabinet (4) in corresponding keyboard/display interface circuit be electrically connected mutually, LED display (6) is loaded on panel left side and is electrically connected mutually with the keyboard/display interface circuit of cabinet (4) interior circuit board; Its circuit is by the pressure to current transmitter circuit, the current/voltage-converted multi-channel analog switch circuit, the temperature current transmitter circuit, the A/D converter circuit, the single chip microcomputer circuit, data memory, serial interface circuit, the memory under program of storage of collected and Control Software, keyboard/display interface circuit, light-emitting diode display is electrically connected formation jointly, and its interconnected relationship is: the pressure to current transmitter circuit is respectively by the pressure transducer output signal line, pressure to current transmitter output signal line, power lead respectively with pressure transducer (1), the current/voltage-converted multi-channel analog switch circuit, power supply is electrically connected mutually; The temperature current transmitter circuit is electrically connected with temperature sensor (2), current/voltage-converted multi-channel analog switch circuit, power supply respectively mutually by temperature sensor output signal line, temperature current transmitter output signal line, power lead respectively; The A/D converter circuit is electrically connected with current/voltage-converted multi-channel analog switch circuit, single chip microcomputer circuit respectively mutually by switching signal output line, the A/D converter output line of current/voltage-converted multiway analog switch respectively; The single chip microcomputer circuit is electrically connected with data-carrier store, program storage, keyboard/display interface circuit respectively mutually by the data-signal output line in the microcomputer bus, program singal output line, keyboard signal incoming line and shows signal output line respectively; Data-carrier store is electrically connected with serial interface circuit mutually by the data storage output signal line; Keyboard/display interface circuit is electrically connected with control key board, light-emitting diode display respectively mutually by keyboard signal output line, LED shows signal output line respectively.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB991172833A CN1174224C (en) | 1999-12-11 | 1999-12-11 | Liquid level measuring instrument and its error compensation method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB991172833A CN1174224C (en) | 1999-12-11 | 1999-12-11 | Liquid level measuring instrument and its error compensation method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1256404A CN1256404A (en) | 2000-06-14 |
| CN1174224C true CN1174224C (en) | 2004-11-03 |
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ID=5279919
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB991172833A Expired - Fee Related CN1174224C (en) | 1999-12-11 | 1999-12-11 | Liquid level measuring instrument and its error compensation method |
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| Country | Link |
|---|---|
| CN (1) | CN1174224C (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2499469A1 (en) * | 2009-11-09 | 2012-09-19 | Koninklijke Philips Electronics N.V. | Flow sensing method with temperature compensation |
| CN102036511B (en) * | 2010-12-01 | 2012-12-12 | 株洲南车时代电气股份有限公司 | Method for classifying and compensating nonlinear variation of core boards for manufacturing multilayer circuit boards |
| CN102235905A (en) * | 2011-04-08 | 2011-11-09 | 海尔集团公司 | Method for correcting error frequency of water level sensor on washing machine |
| CN102288253A (en) * | 2011-07-08 | 2011-12-21 | 厦门大学 | Multi-objective real-time wireless volume detecting system for amorphous liquid |
| CN102645293A (en) * | 2012-04-25 | 2012-08-22 | 无锡商业职业技术学院 | Intelligent pressure transmitter |
| CN104132674A (en) * | 2014-07-31 | 2014-11-05 | 西安交通大学 | Multi-signal output intelligent pressure transmitter |
| CN104316133A (en) * | 2014-11-06 | 2015-01-28 | 江苏华豪航海电器有限公司 | Liquid level measurement device of ship liquid cargo cabin |
| CN105067038A (en) * | 2015-08-10 | 2015-11-18 | 上海峥岚实业有限公司 | Multi-parameter density/ liquid level instrument and manufacture method thereof |
| CN106872059A (en) * | 2017-04-12 | 2017-06-20 | 山东电力设备有限公司 | A kind of oil-filled transformer measurement device of oil tempera and measuring method |
| CN109405925A (en) * | 2018-11-22 | 2019-03-01 | 苏州固宜电子科技有限公司 | Magnetic double level gauge with the reflexive feedback system of pressure |
| CN115014629A (en) * | 2022-06-15 | 2022-09-06 | 广东乐心医疗电子股份有限公司 | Temperature drift compensation method and device for pressure sensor |
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1999
- 1999-12-11 CN CNB991172833A patent/CN1174224C/en not_active Expired - Fee Related
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|---|---|
| CN1256404A (en) | 2000-06-14 |
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