Ohmic transmitter

 

(57) Abstract:

The inventive device includes four electrodes, four core elements, a power source, a measuring device, a processing unit, control unit. Capacity of the first and second electrodes are equal and not equal are equal to the capacitances of the third and fourth electrodes. 7 Il.

The invention relates to the instrument and can be used in various industries for measuring liquid level.

Known resistive sensors, containing the power source, the electrodes and the measuring device (see , for example, U.S. patent N 3089337, CL 73-295, 1963; U.S. patent N 3119266, CL 73-304, 1964; French patent N 2115093, CL G 01 F 28/00, Ageikin D. I. and other Sensors control and regulation. M : mechanical engineering, 1965, S. 401, and so on ). The disadvantages of these sensors is the limited accuracy due to the influence of unknown in advance ohmic resistance of fluids, especially in real operating conditions. For example, the ohmic resistance of the water when measuring its level gateways hydraulic structures are significantly influenced by the impurities (soluble and insoluble).

Known about Arial and connected the ends to the power source (see A. C. the USSR N 777453, CL G 01 F 23/24, 1974). The disadvantage of this sensor is the presence of a signal at a zero level value material.

The closest to the technical nature of the proposed and selected by the authors for the prototype is ohmic transmitter on and. C. the USSR N 535462, CL G 01 F 23/24, 1976, contains the power supply, the low-resistance resistors are coated with a layer of substance, resistivity greater than the resistivity of the controlled fluid, a measuring device, and the electrodes are designed in the form of a double cylindrical helix with a uniform pitch, and the opposite direction of the coils, a longitudinal centerline which is perpendicular to the surface of the liquid.

The disadvantages of this sensor are limited precision of the measurement of liquid level, the complexity of manufacturing and limited functionality. The low accuracy of the measurement is influenced in advance of the unknown resistivity of the liquid on the readings. Requires selection of material for the manufacture of a layer whose resistance greater than the resistance of the liquid, which limits the functionality. The complexity of manufacture due to the necessity of applying a layer of a substance is Uchenie influence on the measurement result in advance of the unknown values of the contact resistance of the liquid between the electrodes of the resistive sensor.

The objective is achieved by the fact that in ohmic transmitter containing the first and second electrodes, connected in series with a power source and a measuring device, inputs of the third and fourth electrodes, a control unit, a processing unit, the first, second, third and fourth key elements, and the resistance of the third and fourth electrodes are not equal to the resistance of the first and second electrodes, the top findings of the first and third electrodes connected respectively to the outputs of the first and second key elements, the top findings of the second and fourth electrodes are combined and connected to the free output of the measuring device, the output of which is connected to the combined inputs of the third and fourth key elements whose outputs are connected respectively to first and second inputs of the processing unit, spare tire power source connected to the combined inputs of the first and second key elements of the control inputs of the first and second key elements are United and connected with the first output control unit, the second output of which is connected to the joint control inputs of the second and fourth key elements.

Sushnost the STI largely depends on the fluid resistance Rtobetween the submerged parts of the electrodes of length lx.

In actual use conditions, for example, when measuring the water level in the gateways of hydraulic structures, the P value is significantly affected by soluble and insoluble impurities. To exclude the effect in advance of the unknown factor Rtoon the measurement result of the proposed use of information redundancy is to measure the level value lxin two cycles.

In the first cycle is measured or the equivalent resistance R1the entire measuring chain including first and second electrodes or the current I1flowing through the measuring circuit (I1= E/R1where E is the EMF of the power supply). The resistance R1= Rx+Rn1+RK1where Rxthe surface resistance value part of length (l-lxthe first and second electrodes; Rn1the resistance of the wires and blocks the measuring circuit of the transmitter in the first cycle of measurements; RK1the resistance of the fluid between the submerged parts of the first and second electrodes.

In the second cycle is measured or the equivalent resistance R2a measuring circuit including a third Yves>= K Rx+Rn2+RK1where KRxthe surface resistance value part of length l-lxthe third and fourth electrodes (on the condition that the resistance of the third and fourth electrodes are not equal to the resistance of the first and second electrodes); k - coefficient of proportionality between resistance electrodes (K > 0, K 1); Rn2the resistance of the wires and blocks measuring circuit sensor in the second measurement cycle, the; RK2the resistance of the fluid between the submerged parts of the third and fourth electrodes.

If R= RK2, Rn1Rn2then

Rx= (R1-R2). (1)

or

Rx= - . (2)

Knowing Rxyou can determine the current value of the liquid level.

Distinctive features of the proposed technical solutions are: introduction of the third and fourth electrodes; the introduction of the control unit; introducing a processing unit; the introduction of four key elements; the resistance of the third and fourth electrodes are not equal to the resistance of the first and second electrodes; links between the known and the newly introduced elements.

Signs - introduction four key elements and connection of the control inputs matched with the parameters for control systems and measurement. M : Energy. 1976, S. 127, Fig. 2-43) and used for its intended purpose.

Sign - introduction to the unit clerk to issue control pulses at certain points in time is known (see , for example, Martsin A. I. and other Converters electrical parameters for control systems and measurement. M : Energy, 1976, S. 129, Fig. 2-45) and is used for its intended purpose.

The authors found no technical solutions to the level in which you would use such features as the use of the third and fourth electrodes, the resistance of which is not equal to the resistance of the first and second electrodes; the use of information redundancy to improve the measurement accuracy.

According to the authors, these signs are significant, the use of which allows to increase the measurement accuracy by eliminating the influence of difficult-to-estimate factors.

In Fig. 1 shows a block diagram of the flow sensor of Fig. 2 is a variant of the technical implementation of the control unit of Fig. 3 is a variant of the technical implementation of the processing unit of Fig. 4 - layout of the electrodes in the vessel to ensure equality of resistance of the fluid between the first and the key information when used as a measuring device ammeter; in Fig. 6 diagram of the memory element of Fig. 7 is a connection diagram of the electrodes.

In Fig. 1-5 adopted codes:

l is the length of the electrodes 1.1, . . , 1.4;

lx- the current value of the liquid level;

l-lx- surface part of the electrode (the length of the electrodes located above the liquid level); h is the distance from the lower end of the electrodes 1.1, . . . , 1.4 to the bottom of the tank; - the distance between the electrode 1.1 (1.3) and the electrode 1.2 (1.4).

Ohmic transmitter (Fig. 1) contains four electrodes 1.1, 1.2, 1.3, 1.4, four key elements 2.1,. . . . , 2.4 power supply (source EMF) 3, the measuring device 4, the processing unit 5, unit 6, the control electrodes 1.1,. . . . 1,4 made of the same length l and placed vertically at the same distance h from the bottom of the tank 7, the resistance values of the electrodes 1.3, 1.4 K times (K > 0, K 1) is greater than the resistance values of the electrodes 1.1, 1.2, upper output electrode 1.1 (1.3) is connected to the output key element 2.1 (2.2), the upper terminals of the electrodes 1.2, 1.4 United and connected with the first output of the measuring device 4, the second terminal of which is connected to the first (negative) bus power source 3, the second (zero) bus which is connected to the integrated information inputs the key elements 2.3, 2.4, the outputs of which are connected respectively with the first and second inputs of the processing unit 5, the control inputs of the key elements 2.1, 2.3 integrated and connected to the first output of the control block 6, the second output of which is connected to the joint control inputs key elements 2.2, 2.4.

The distance between the electrodes 1.1 and 1.2, as well as between the electrodes 1.3 and 1.4 are equal.

The power source may be in the form of the AC source.

The electrodes 1.3, 1.4 can be made of the same material as the electrodes 1.1, 1.2. but different cross-sectional area, or of great material the same configuration.

The electrodes 1.1, . . . , 1.4 to increase the sensitivity can be made in the form of a double cylindrical helix with a uniform or uneven step and the opposite direction of coils similar to the immersion of the electrodes. C. the USSR N 535462, 974133.

The key elements of a well - known elements (see , for example. Sidorov A. C. Diode and transistor switches. -M. : Communication, 1975; Switches analog signals on the semiconductor elements. Ed. by J. P. white. M : Energy, 1976; Orchowski C. F. Circuit switching analogdialogue can be used a known programmable pulse generator.

Technical implementation of programmable pulse generators are known (see , for example, a Programmable pulse generator for testing an ENCORE Express information (EI), vol. LEA, 1972, N 41, Ref. 163; "Programmable synchronous single-pulse generator", EI, vol. LEA and WATTS, 1979, No. 28, Ref. 162; "Tunable pulse generator", EI, vol. LEA and WATTS, 1977, N 37, Ref. 210; "the Generator of sequences of pulses, Switzerland. Pat. N 543835, publ. 14.12.73, and so on ).

In Fig. 2 is a diagram of one embodiment of the technical implementation unit 6 of the control.

Unit 6 controls (Fig. 2) contains the generator 8 pulses, the counter 9, the decoder 10, the bus 11 is zero and the bus start 12, while the output of the generator 8 pulses is connected to the counting input of the counter 9, the generalized output of which is connected with the generalized input of the decoder 10, the two outputs of which are connected respectively to the first and second outputs of the control block 6, to the input set to zero the meter 9 connected to the bus 11 zero to the input of the oscillator start-up 8 pulses connected bus "start" 12.

Under the generalized exit (entrance) refers to multi-wire output (input). Bus 11 zero and the bus start 12 via the button with the return connected to further the holding element 13 memory the adder 14, the scaling amplifier 15, the indicator 16, and the output of the memory element is connected to the first (summing) the input of the adder 14, the output of which is connected to the input of a large-scale amplifier 15, the output of which is connected to the input of the indicator, the first input unit 5 computing is an information input of the memory element 13, a second input, a United control input of the memory element 13 and the second (subtractive) input of adder 14.

The memory element 13 (Fig. 3) can be implemented based on the device selection-retention (water economy Department). The function of the memory element is storing on the storage capacitor for some time instantaneous input voltage. In sampling mode, the water economy Department of repeats of the input signal, and then on command stores the instantaneous value and goes into storage mode.

In Fig. 5 shows a second variant of the technical implementation of the processing unit 5. Unlike unit 5 shown in Fig. 3, the processing unit 5 (Fig. 5) further comprises two blocks 17.1, 17.2, nonlinearity implement the function y= 1/x, where x is the input signal; y - output. While the unit output nonlinearities 17.1 is connected to the input of the memory element 13, and the output unit nonlinearities 17.2 - W is the ring entrance - the combined input nonlinearities 17.2 and the control input of the memory element 13.

Blocks nonlinearity 17.1, 17.2 can be implemented on the basis of the block division circuit which is given in the book of U. Titze, K. Schenk "Semiconductor circuit", M. : Mir, 1982, S. 163, Fig. 11.42, S. 166, Fig. 11.46. In this case, the input of the fissionable unit served a single signal from the secondary power source (Fig. 5 not shown), and the output signal of the measuring device 4 is input to divider block division.

As the measuring device 4 can be used ammeter (current sensor) or an ohmmeter. Technical implementation of the ammeters with electrical outlet found in the literature (see , for example, U. Titze, K. Schenk. Semiconductor circuitry. M. : Mir, 1982, S. 469, Fig. 25.6, 25,7).

Ohmic transmitter (Fig. 1) using an ohmmeter as the measuring device 4 operates as follows. In this case, the processing unit 5 has a technical solution, is shown in Fig. 3.

In the initial state, the control block 6 (Fig. 2) bus 11 zero signal to the input of the zero of the counter 9 and set its contents to zero.

So kakrani zero.

Suppose that you want at a certain point in time to determine the level of lxthe liquid in the vessel 7 (Fig. 1).

In block 6 of the control (Fig. 2) bus start 12 serves a signal to start the generator 8 pulses, which starts to produce pulses with a predetermined frequency. The data pulses to the counting input of the counter 9, which considers them. The signals from the outputs of the counter 9 are fed to the inputs of the decoder 10. At some time t1on one of the outputs of the decoder 10 of a signal, which is supplied to the first output of the processing unit 5. This signal is fed to the control inputs of the key elements 2.1, 2.3 (Fig. 1), opening them.

The following circuit: positive bus of the power source 3 is a key element 2.1 - electrode 1.1 - the liquid in the tank 7 between the electrodes 1.1, 1.2 - electrode 1,2 - measuring device 4 to the negative bus of the power source 3 - flow current I1.

The measuring device 4 will measure the equivalent resistance

R1= = Rx= Rk1+Rn1, (3) where Rx- the resistance of a part of the electrodes 1.1, 1.2, above the liquid level, proportional to the value l-lx; RK1the resistance of the fluid between the submersible parts electrotrance resistance measuring device 4, source 3 power, open the key item 2.1);

E - the value of the EMF source 3 power (output voltage).

A voltage proportional to R1with the output of the measuring device 4 through the open key element of 2.3 is fed to the first input unit of the information processing information processing 5. In block 5 (Fig. 3) this signal is applied to the information input of the memory element 13, which stores it.

Then at time t2a signal on the second output of the control block 6, and the signal on the first output unit 6 of the control is equal to zero. While the key elements 2.1, 2.3 closed and opened the key elements 2.2, 2.4;

The following circuit: positive bus of the power source 3 - open key element 2.2 - electrode 1.3 - the liquid in the tank 7 between the electrodes 1.3, 1.4 measuring device 4 to the negative bus of the power source 3 - flow current I2.

The measuring device 4 will measure the equivalent resistance of the circuit equal to

R2= = kRx+Rk2+Rn2, (4) where (K Rx- the resistance of a part of the electrodes 1.3, 1.4 above the liquid level proportional to the value of 1.3, 1.4;

RK2the resistance of the fluid between the submerged parts of electrotrance resistance of the power source 3, the measuring device 4, the outdoor key element 2.2).

The output signal of the measuring device 4, is proportional to R2through the opened key element 2.4 is applied to a second input of the processing unit 5.

In the processing unit 5 (Fig. 3) this signal is applied to the control input of the memory element 13 and the second (subtractive) input of adder 14. At the output of the memory element 13 will receive a signal proportional to R1served on the first (summing) the input of the adder 14. The output signal of the adder 14 y(R1-R2). When RK1RK2. RRn2. y(1-K) Rx. The output signal of the adder 14 y14served on a log-scale amplifier 15 with the gain | 1/(1-K)| . The output signal of the amplifier 15 will be proportional to the value of Rxwhose value is displayed in the indicator 16. If the indicator 16 to traderoute accordingly, his testimony will meet will meet the current value of the liquid lxin the vessel 7.

If the measuring device 4 is used, the ammeter, the processing unit 5 has the technical implementation, shown in Fig. 5. In this case, the ohmic level is al

I1= , where E is the EMF of the power source 3.

The signal y4served in block 5 of measurements on the input nonlinearity 17.1 whose output is y17.1= 1/y4= (Rx+RK1+Rn1)/E is stored in the memory element 13.

In the second measurement cycle, the level at the output of the measuring device 4, a signal will appear y I2= that in the processing unit 5 (Fig. 5) is input to block nonlinearities 17.2 and to the input of the memory element 13. The output signal of the block nonlinearities y17.2= is fed to the subtractive input of the adder 14, a summing input of which the output element 13 of the memory signal y17.1. The output signal of the adder 14, provided that R RK2, Rn1Rn2equal to the value of y14= R . Signaluserved on a log-scale amplifier 15 with a gain . The output signal of the large-scale amplifier 15 y5proportional to Rx, is input to the indicator 16. Indicator 16 will be proportional to Rxand, accordingly, proportional to the value of lx(with proper calibration).

To ensure equality of RK1= RK2the electrodes 1.1, . . . , 1.4 perform the same geometric fo the s side of the square.

In this case, to eliminate the influence of the electrodes on each other can be connected to the upper terminals of the electrodes 1.2, 1.4 relevant key elements (2.5, 2.6) whose outputs are combined and connected to the corresponding output of the measuring device. The control inputs of the key elements 2.1 (2.2) and 2.5 (2.6) combined (Fig. 7).

To synchronize the operation before the second input of the adder 14 is possible to put a delay element (delay line).

As the information input element 13 memory signal is equal to zero (a key element 2.3 is open, its contents will be zero.

The cycle of measurement of liquid level ends. If necessary, the measuring cycle is repeated.

The liquid level can be measured with a periodicity = t2. When this generator 8 pulses per unit 6 management works continuously. On the respective outputs of the control block 6 will receive the signals that control as described above, the operation of the level gauge.

As a result of application of the proposed sensor improves the accuracy of measuring the current value of the fluid due to the exclusion of the impact in advance of the unknown values of the contact resistance (resisting film to prevent the of Strogov in the form of a double helix with the opposite direction of coils; increases reliability by eliminating mechanical moving parts; increases reliability by eliminating the influence of fouling submersible electrodes in real operating conditions. The electrical resistance of the fouling is included in RKthat this technical solution does not affect the measurement result.

(56) USSR Author's certificate N 535462, CL G 01 F 23/24, 1974.

OHMIC TRANSMITTER containing the first and second electrodes with equal resistances and connected in series with a power source and a measuring instrument connected to the upper conclusion of the second electrode, characterized in that it introduced the third and fourth, connected to the measuring device, the electrodes, the control unit, from the first to the fourth key elements and the processing unit, the input of which is connected to the outputs of the third and fourth key elements, the first and second inputs which are connected to the outputs respectively of the control unit and measuring device to the second input of which is connected the first power supply output, the second output of which is connected to the first inputs of the first and second key elements to the second inputs of which are connected what avimi elements, and the resistance of the third and fourth electrodes are equal and not equal to the resistance of the first electrode.

 

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