Resistive sensor (options)

 

(57) Abstract:

The inventive device according to the first embodiment includes four flat electrode, two power supply, two measuring device, the computing unit. Electrodes are placed on the sides of the square. The device according to the second variant contains three flat electrode, the power source, two measuring device, the computing unit. Electrodes are placed on the sides of an equilateral triangle. 2 S. and 2 C.p. f-crystals, 7 Il.

The invention relates to the instrument and can be used to measure liquid level.

Known ohmic transmitter containing the power source, the electrodes and the measuring device [1].

The disadvantage of this sensor is limited precision due to the influence of unknown in advance ohmic resistance of the liquid.

Known ohmic transmitter containing the sensor, made in the form of a steel tube immersed in the electrically conductive material and connected to the power source [2].

The disadvantage of this sensor is the presence of a signal at the zero value of the liquid level.

The closest in technical essence to scoonie resistors, covered 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 [3].

The disadvantage of this sensor is limited precision of the measurement of liquid level, due to the influence of in advance of the unknown resistance of the liquid.

The purpose of the invention is the limited accuracy of the measurement of liquid level.

The aim is achieved in that in the first embodiment of the technical solution proposed sensor containing the first and second electrodes, the first power source and the first measuring device included in the circuit connecting the upper terminals of the electrodes, have been added to the second power source and the second measuring device in the circuit connecting the upper conclusions have been added to the third and fourth electrodes, the electrical resistance of which is not equal electrical resistances of the first and second electrodes, the first and second measuring devices connected to vvedeno the m square.

In the second embodiment of the technical solution proposed sensor containing the first and second electrodes, the power source and the first measuring device included in the circuit connecting the upper terminals of the electrodes, inputs of the second measuring device, the third electrode and the computing unit, the second measuring device included in the circuit between the upper output of the third electrode and the power source, and first and second measuring devices connected to the computing unit.

Optionally, the electrodes are made flat and are located in the plan on the sides of an equilateral triangle.

The essence of the proposed invention consists in the following. In ohmic gauge the accuracy of the measurement of liquid level largely depends on the fluid resistance Rkbetween the immersed part of the electrode length lx.

In actual use conditions, for example, when measuring the water level in the gateways of hydraulic structures, the value of Rksignificantly affected by soluble and insoluble impurities. To exclude the effect in advance of the unknown factor Rkon the measurement result of the proposed use of the principles of circuit and entreprene R1the first measuring circuit including first and second electrodes or the current I1flowing through the measuring circuit I1=E1/R1where E1- the value of the EMF of the first power source. 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 scheme of measurement; Rk1the resistance of the fluid between the submerged parts of the first and second electrodes.

The second measuring device measures or the equivalent resistance R2a measuring circuit including third and fourth electrodes or current I2=E2/R2flowing through the measuring circuit. Co - resistance R2= KRx+R+R , where KRxthe surface resistance value part of length l-lxthe third and fourth electrodes; K - coefficient of proportionality (K> 0, K1); Rn2the resistance of the wires and blocks the second measuring circuit; Rk2the resistance of the fluid between the submerged parts of the third and fourth electrodes; E2- the value of the EMF of the second power source.

Engl is cosee value of the liquid level lx. As follows from (1), (2), the result of the measurement of liquid level lxdoes not depend on Rk.

The authors found no technical solutions to the level in which you would use such features as the use of structural redundancy to improve the accuracy of estimation of level of the liquid by introducing an additional measuring circuit. The execution of the electrodes are flat, and location them in the plan in the form of an equilateral triangle or square increase accuracy at the expense of equality resistance of the liquid between the electrodes.

Therefore, these signs can be attributed to 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 first variant of ohmic transmitter of Fig. 2 is a variant of the technical implementation of the block; Fig. 3 - layout of the electrodes in the tank in plan the sides of the square; Fig. 4 is a variant of the technical implementation of the block when used as a measuring device the measuring device of Fig. 5 is a variant of the technical implementation of the second version of the sensor of Fig. 6 and 7 embodiment of the electrodes is Uchenie liquid level; l-lx- surface part of the electrode (the length of the electrodes, the location 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, ..., 1.4, two sources 2.1, 2.2 power supply, two measuring unit 3.1, 3.2, the computing unit 4, and the electrodes 1.1, . .., 1.4 placed in the vessel 5, the liquid level in which you want to measure, the upper output electrode 1.1 (1.3) is connected to the first output of the measuring device 3.1 (3.2), the second terminal of which is connected to one output source 2.1 (2.2) power supply, the second terminal of which is connected to the upper output electrode 1.2 (1.4), the outputs of the measurement devices 3.1, 3.2 are connected respectively with the first and second inputs of the computing unit 4.

The resistance of the electrodes 1.3, 1.4 times (>0, 1) is greater than the resistance of the electrodes 1.1, 1.2. The electrodes 1.3, 1.4 can be made of the same conductive material as the electrodes 1.1, 1.2, but other cross-section, or the same geometric shape as the electrodes 1.1, 1.2, but made of a different material from a material with a different resistivity).

The electrodes 1.1, ..., 1.4 can empathic current) or ohmmeter.

As the measuring device 3 may use the Converter resistance in the voltage.

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.

A computation (Fig. 2) contains an adder 6, a large-scale amplifier 7 and the indicator 8, while the output of the adder 6 is connected to the input of a large-scale amplifier 7, the output of which is connected to the input of the indicator 8, and the first and second inputs of the computing unit 4 are summarizing and subtractive inputs of the adder 6.

A computation (Fig. 4) contains an adder 6, two large-scale amplifier 7.1, 7.2, indicator 8, two blocks 9.1, 9.2 division, and the output unit 9.1 (9.2) division is connected to the input of a large-scale amplifier 7.1 (7.2), the outputs of large-scale amplifiers 7.1, 7.2 are connected respectively to the first (summing) and second (subtractive) inputs of the adder 6, the output of which is connected to the input of the indicator 8, the first and second outputs of the computing unit 4 are respectively inputs of large-scale amplifiers 9.1, 9.2.

The transmitter (Fig. 5) contains three electrodes 1.1, 1.2, 1.3, source 2 power supply, two measuring unit 3.1, 3.2, block 4 calc output measuring device 3.1 (3.2), the latter findings are combined and connected to one output of the source 2 power supply, the second terminal of which is connected to the top output electrode 1.2, the outputs of the measurement devices 3.1, 3.2 are connected respectively with the first and second inputs of the computing unit 4.

Ohmic transmitter (Fig. 1) using an ohmmeter as the measuring device 3 operates as follows. In this case, the block 4 has a technical solution, is shown in Fig. 2.

The measuring device 3.1 measure the equivalent resistance

R1= = Rx+R,+R, (3) where Rx- the resistance of a part of the electrodes 1.1, 1.2 located above the liquid level, proportional to the value l-lx;

Rk1the resistance of the wires and blocks in the first dimension diagram (internal resistance measuring device 3.1, 2.1 source power);

E1- the value of the EMF source 2.1 power supply (output voltage);

I1the current flowing in the first circuit of the measuring circuit.

The measuring device 3.2 measure the equivalent resistance of the circuit equal to

R2= = KRx+R,+R, (4) where K.Rx- the resistance of a part of the electrodes 1.3, 1.4, above the liquid level;

R - with the measuring circuit in the second measurement (the internal resistance of the source 2.2 power the measuring device 3.2);

E2- the value of the EMF of the second source 2.2 power;

I2the current flowing in the circuit of the second measuring circuit.

The output signals of the measuring devices 3.1, 3.2, proportional, respectively, R1, R2served on the first and second inputs of the computing unit 4. In the computing unit 4 (Fig. 2) these signals are fed respectively to the accumulating and subtractive inputs of the adder 6. The output signal of the adder 6 is input to the large-scale amplifier 7 with gear ratio 1/(1-K). The output signal of the amplifier 7, is proportional to Rxwill be displayed in the indicator 8. If the indicator 8 to traderoute accordingly, the indication will correspond to the current level value lx.

Large-scale amplifier 7 may be eliminated. Then the indicator 8 will display the value (1-K)Rx. Since K=const, then, using a special calibration of the indicator 8, you can display the value of lx.

When used as a measuring device 3.3 (3.2) sensor current sensor (Fig. 1) works as follows.

In this case, the computing unit 4 has the technical implementation is provided in Fig. 4. While the devices 3.1, 3.2 proportional to the currents I1, I2in the computing unit 4 (Fig. 4) are fed respectively to the inputs of blocks 9.1, 9.2 division. The output signal of the block 9.1 division proportional to the value of 1/I1served on a log-scale amplifier 7.1 with transfer factor E1/(1-K). The output signal of the block 9.2 division, proportional to the value of 1/I2served on a log-scale amplifier 7.2 with transfer factor E2/(1-K). Output signals mashstabnyh amplifiers 7.1, 7.2, proportional to the values of and are given correspondingly to the accumulating and subtractive inputs of the adder 6, the output of which is provided that R R, R R, is proportional to the value of Rxthat will be displayed on the display 8.

To ensure equality of Rk1= Rk2the electrodes 1.1, ..., 1.4 carry out flat and have in plan the sides of the square (Fig. 3), while the electrodes 1.1 (1.3) and 1.2 (1.4) are located on opposite sides of the square.

The transmitter (Fig. 5) works as follows.

The measuring device measures 3.1 current I1=E/R1where E is the EMF of the source 2 power. Current I1, I2an input unit 4 calculations. In the computing unit 4 (Fig. 4) output signal summation.

In this arrangement, the resistance of the circuit electrode 1.1 - electrode 1.2 must be equal to the resistance of the circuit electrode 1.3 - electrode 1.2.

The arrangement of the electrodes in the plan on the sides of an equilateral triangle (Fig. 6) ensure equality Rk1Rk2. The electrodes thus made flat.

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 (the resistance of the liquid between the submerged parts of the electrodes; 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 result of measurement; the measurement process is carried out continuously in real-time.

1. Ohmic transmitter containing the first and second electrodes, the first power source and the first measuring device included in the circuit connecting the upper terminals of the electrodes, characterized in that nbody additionally introduced the third and fourth electrodes, electrical resistance which is not equal electrical resistances of the first and second electrodes, the first and second measuring devices are connected to the input block.

2. The sensor under item 1, characterized in that the electrode is planar and located in plan the sides of the square.

3. Ohmic transmitter containing the first and second electrodes, the power source and the first measuring device included in the circuit connecting the upper terminals of the electrodes, characterized in that it introduced the second measuring device, the third electrode and the computing unit, the second measuring device included in the circuit between the upper output of the third electrode and the power source, and first and second measuring devices connected to the computing unit.

4. The sensor on p. 3, characterized in that the electrode is planar and are located in the plan on the sides of an equilateral triangle.

 

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