A method of measuring the liquid level

 

(57) Abstract:

Usage: for level measurement. The inventive measure the resistance R1in the circuit between the immersed electrodes, changing the depth of immersion of the electrodes to measure the resistance R2in the circuit between the immersed electrode after changing the depth of their dives, determine the liquid level. Given a mathematical expression for the calculation of the level. 7 Il.

The invention relates to the instrument and can be used for level measurement of conductive liquids with the use of immersion of the electrodes.

Known electrothermal method for measuring liquid level (see patent Germany N 3423802, CL G 01 F 32/24, 1986), based on the measurement of the resistance of the submersible electrode made in the form of the heated resistor with a positive temperature coefficient.

The disadvantage of this method is the limited accuracy due to the influence of the ambient temperature.

There is a method of liquid level measurement based on measuring the resistance between the immersed electrodes (see N.A. Morehow. Automatically measuring volume, level and Paris precision level measurement.

The prototype of the invention is a method of measuring the level in U.S. Pat. RF N 2008625, CL G 01 F 23/24, 1994), implying that the measured resistance R1in the circuit between the first and second electrodes, the change in the resistance of the electrodes in the "to" time, measure the resistance R2in the circuit, and the liquid level lxdetermined by the formula:

,

where

S the cross-sectional area of the electrode;

the resistivity of the electrodes (>0, K1).

The disadvantage of this method is limited scope because of the need to change the resistivity of the electrodes, which requires the use or non-standard electrodes, or electrodes, connected in parallel to the first.

The technical result of the use of the invention is to extend the scope of application of the method by allowing the use of standard electrodes.

This result is achieved due to the fact that in the method of measuring the level of liquids, which consists in measuring the resistance R1in the circuit between the first and second electrodes, which are level value, additionally measure the depth on D, measure the resistance R2in which R0= l0/Sethe resistance of the electrodes;

the resistivity of the electrodes;

Sethe cross-sectional area of the electrodes;

l0the length of the electrodes;

< / BR>
when lowering the electrodes

.

The invention consists in the following. Accuracy ohmic level significantly affected in advance unknown or difficult-to-estimate the contact resistance of the liquid Rtobetween the submerged parts of the electrodes. This situation occurs for example when changing the water level in the gateway, when the value of Rtodepends on weather conditions (moisture, temperature), various impurities of organic and or inorganic origin.

to exclude the effects of Rtoon the measurement result lxuse of information redundancy measurement is carried out at two values of the depth of immersion of the electrodes.

The hallmark of the proposed method of measurement is the change in the depth of immersion of the electrodes in the second cycle of measurement.

In Fig.1 presents a diagram of the device that implements the proposed method of measurement, with one pair of electrodes; Fig.2 diagram of the device, izobretaya, implements the proposed method of measuring the level, having two pairs of electrodes are shifted vertically relative to each >0 in Fig.4 scheme of an automatic level gauge of Fig. 5 version of the technical implementation unit of the automatic calculation of the transmitter of Fig. 6 the second option is the technical implementation of the block; Fig.7 the third variant of the technical implementation unit of computing.

Device for level measurement (Fig.1) contains two electrodes 1, 2 and the measuring device 3, and the electrodes 1, 2 are placed into the container 4 with the measured liquid.

In the device (Fig.2) the electrodes 1, 2 is installed with excess height >0 in comparison with the electrodes in the device shown in Fig.1 ( (<l) ).

The device (Fig.3) contains an additional pair of electrodes 5, 6 and switch 7 in comparison with the device, which is shown in Fig.1 or in Fig.2. While the electrodes 5, 6, is identical to the electrodes 1, 2, are moved vertically relative to the electrodes 1, 2 (for example, up to the amount >0(<l) The upper terminals of the electrodes 1, 2 are connected to the NC contact of the switch 7, and the upper terminals of the electrodes 5, 6 for closing the switch contacts shall be made in the form of a rectangular plate of length l0width d, the area in terms of Seand located at a distance from each other. As the measuring device can be used an ohmmeter.

The transmitter (Fig. 4) contains four electrodes 1, 2, 5, 6, dual power 8, 9, two measuring device 3, 10, block 11. When the electrodes 1, 2, 5, 6 placed in the tank 4, the liquid level in which you want to measure. The upper output electrode 2(6) is connected to the first output of the measuring device 3(10), the second terminal of which is connected to one pin of the power source 8(9), the other output of which is connected to the top output electrode 1(5). The outputs of the measuring devices 3 and 10 are connected to first and second inputs of the computing unit, respectively.

The electrodes 5, 6, height-shifted by D>0 with respect to the electrodes 1, 2. In Fig. 4 shows that the electrodes 5, 6 are raised with respect to the electrodes 1, 2.

The resistance of the electrodes are equal to each other and the electrodes are made of the same type.

The computing unit 11 (Fig.5) contains a DC voltage sources 12, 13 in the General case of a regulated adders 14, 15, the element division 16 indicator 17, and the output of source 12 is connected to a summing input of the adder 14, the output of a source 13 p the second inputs of the element division 16, the output of which is connected to the indicator 17, the first input of the computing unit 11 is the second summing input of the adder 15, a second input combined subtractive inputs of the adders 14, 15.

In block 11 (Fig.6) to the subtractive input of the adder 14 is connected to the output of the source 12, the first subtractive input of the adder 15, the output of the source 13. The outputs of the adders 14, 15 connected responsively to the first and second inputs of the element division 16, the output of which is connected to the input of the indicator 17, the first input of the computing unit 11 is a summing input of the adder 15, a second input of the United summing input of the adder 14 and the second subtractive input of the adder 15.

The computing unit (Fig. 7) contains two analog-to-digital Converter /ADC/ 18, 19, the microprocessor /personal computers or microcomputers/ 20 and the led 17, and the outputs of the ADC 18, 19 are connected to first and second inputs of the microprocessor 20, respectively, the output of which is connected to the input of the indicator 17, while the first and second inputs of the block are respectively the inputs of the ADC 18, 19.

The process of measuring the liquid level is two cycles.

In the first cycle, measure the resistance in the circuit between the immersed electrodes )Se= (R0-0lx/Se) the resistance of a part of the electrodes 1, 2 length (l0-lxlocated above the liquid;

0the resistivity of the electrodes 1, 2;

Sethe cross-sectional area of the electrodes;

R0=0l0/Sethe ohmic resistance of the electrodes;

Rk1=x/lxd contact resistance of the liquid;

xrequired specific resistance of the liquid between the electrodes 1, 2;

l0the length of the electrodes;

the distance between the electrodes 1, 2;

d the width of the electrodes;

lxthe current value of the liquid level.

Then

In the second cycle was measured resistance R2when reducing the depth of immersion of the electrodes 1,2 on the value of <l(>0) /when raising/.

If this

< / BR>
where Rabout=about/Se< / BR>
From (4) and (5) it follows that

< / BR>
In Fig.3 shows the use of two pairs of electrodes, the electrodes 1,2 lowered in comparison with the electrodes 5,6, >0(<l)

In the first measurement cycle, the switch 7 is in position 1. The measuring device 3 measures the resistance R1/see formula (4)/. In the second cycle of ismere (5)/. The liquid level is determined by the formula (6).

With the increase of immersion of the electrodes 1,2 on value (<(l-lx)) in the second measurement cycle, the value of resistance R2has the look /see Annex/:

< / BR>
From (4) and (7) should

< / BR>
Analysis (6), (8) indicates that the measurement result lxdoes not depend on beforehand unknown valuexValues of R0calculated in advance

Automatic transmitter /Fig. 4/ when used as a measuring device ohmmeter works as follows. In this case, the block has the technical implementation, shown in Fig.5. Thus, in block 11, the output signal of the source voltage 12 is set equal to a source

The measuring device 3 measures the equivalent resistance

R1RE1+ RK1< / BR>
Provided that electrodes 1,2,5,6 made in the form of a rectangular plate of length l0width d and area in terms of Sethen

< / BR>
The resistance RE1represents the resistance of the electrode 1,2, located above the liquid level, proportional to the length (l0-lx). The resistance RK1the resistance of the liquid between podruzny is th R2RE2+ RK2,

where

RE2the resistance of a part of the electrodes 5,6 located above the liquid level length (l0-lx);

RK2the resistance of the liquid between the submerged parts of the electrodes 5, 6;

< / BR>
The output signals of the measuring devices 8, 10, proportional, respectively, R1, R2serves respectively to the first and second inputs of the computing unit 19 (Fig.5).

In block 11 (Fig.5) a signal proportional to R1, is applied to a second summing input of the adder 15, the first summing input of which is fed the output signal source 13 a Signal proportional to R2served on the subtractive input of the adder 15 and the subtractive input of the adder 14, a summing input of which is supplied the output signal from the source 12.

The output signal of the adder 14

< / BR>
The output signal of the adder 15

< / BR>
The output signals of the adders 14, 15 serves to corresponding inputs of element division 16, the output of which is

< / BR>
is input to the indicator 17, the reading of which may be calibrated in units of length.

Consider the operation of the transmitter in the case where the electrodes 5,6 located on the magnitude of D>0 SJ are equal . This signal is applied to the subtractive input of the adder 14. The output voltage of the source 13 is fed to the first subtractive input of the adder 15, the second input unit 11 connected to a summing input of the adder 14.

When the sensor output signal of the measuring device 10 is equal to

< / BR>
where

< / BR>
Then

< / BR>
The output signals of the measuring devices 3, 10, respectively, R1and served on the first and second inputs of the computing unit 11. In block 11, the signal proportional to R1served on summing input of the adder 15, the first and second subtractive inputs of which the signals output from the measuring device 3, is proportional to R1and from the output of the source . The output signal of the measuring device 10, proportional , is fed to a summing input of the adder 14, the subtractive input of which is fed the output signal of source 12

The output signal of the adder 14

< / BR>
The output signal of the adder 15

.

The output signals of the adders 14, 15, respectively , are fed to the inputs of the element division 16, the output of which is

< / BR>
is input to the indicator 17.

The computing unit 11 (Fig.7) works as follows.

adultsa to the inputs of the ADC 18, 19, in which signals proportional to R1, R2converted into coded signals /codes/ Y18, Y19. The output signals of the ADC 18, 19 are fed to the inputs of the microprocessor /microcomputers/ 20, which by the formulas (1) or (2) calculates the value of the level lxdisplayed in the indicator 17.

A method of measuring the liquid level, implying that the measured resistance R1in the circuit between the first and second electrodes, which are level values, characterized in that it further alter the depth of immersion of the electrodes to measure the resistance R2in the circuit, and the liquid level lxis determined by the formula:

when lifting the electrodes

< / BR>
where R0=0l0/Se- resistance electrodes;

0- the resistivity of the electrodes;

Sethe cross-sectional area of the electrodes;

l0the length of the electrodes;

< / BR>
0<

0<<(l-lx).x

 

Same patents:

Contact sensor // 2077030

The invention relates to the instrument and can be used for level measurement of conductive liquids with the use of submersible electrodes

The invention relates to the field of measuring probes designed to determine whether the location of the probe conductive material in granules or in liquid form

The invention relates to devices for automatic control of tank filling bulk and liquid conductive materials, such as coal, rock, silo, flour, slurries, chemicals, etc

The invention relates to devices for automatic control of tank filling bulk and liquid conductive materials, such as coal, rock, silo, flour, slurries, chemicals, etc

Ohmic transmitter // 2047843

FIELD: measuring engineering.

SUBSTANCE: device comprises fuel level indicator and rheostat pickup made of an analogue-digital converter with the balance input. The three-position switch is connected with the lever indicator. The device additionally has three resistive dividers, voltage stabilizer, and shunting resistor made of a 0.003-0.006-Om resistor. The rheostat level pickup is mounted inside the fuel tank vertically, and its linear horizontal size at this level is directly proportional to the area of the tank section in the horizontal plane at this level.

EFFECT: expanded functional capabilities.

1 dwg

FIELD: measuring engineering.

SUBSTANCE: method comprises pressing unit reinforced by electrodes with simultaneous forming of insulator between the electrodes. The space that is defined by surfaces of the electrodes is filled with casting plastic mass. The pressure tightness is provided by tightening the insulator with electrodes by means of a nut.

EFFECT: enhanced reliability.

1 dwg

FIELD: the invention refers to measuring technique and may be used for controlling bulk and liquid materials.

SUBSTANCE: the oscillating indicator of a level has a sensible element( a probe) 1 connected with an anchor 2, a driving arrangement 4 in the shape of a coil with a ferromagnetic core and also a sensor 5 of the displacements of the anchor, a drive-pulse generator 6 and an amplifier 7 and a relay block 9 successively connected. The amplifier is spanned with a regulated negative feedback fulfilled in the shape of a resistor 8. The sensor 5 of the displacements of the anchor may be fulfilled in the shape of a coil with a ferromagnetic core. At that the section of the anchor 2 between the coils is fulfilled out of non-magnetic material that prevents electromagnetic connection between the coils providing protection from high frequency oscillations in the system anchor-coil-amplifier.

EFFECT: allows to control the levels of the bulk and liquid materials being present in aggressive mediums, under pressure,( discharge)and at temperature till 200 degrees.

2 dwg

Level meter sensor // 2276333

FIELD: instrument engineering.

SUBSTANCE: level meter sensor comprises hollow rigid base with the port in its bottom end, diaphragm, strain gage converter with box, flexible spacer arranged over periphery of the box, and tube whose one end is mounted pressure-tightly in the port of the support and the other end is connected to the space of the box. The diaphragm is made of a rigid material and mounted on the flexible spacer for permitting cooperation with the strain gage converter.

EFFECT: enhanced reliability and simplified structure.

1 dwg

FIELD: the invention refers to the field of instrument making and designed for control of the level of dielectric and current conducting liquids in hydraulic systems (fuel, freezing, accumulative etc) for example the level of oil or cooling agent in transport vehicles.

SUBSTANCE: the liquid level meter has a two-electrode capacitance sensor with an external 10 and interior 11 electrodes electrically connected with an electronic scheme having a stabilized source of power supply, an amplifier, a generator and a trigger. According to the first variant the capacitance sensor is fulfilled in the shape of a coaxial condenser "C". The interior electrode 11 of the sensor is fulfilled tubular and is mounted inside a fluoroplastic probing rod 12. The interior electrode 11 is connected to the input of a phase comparator which is additionally introduced in the scheme and whose output is connected with input of the trigger and the output of the last is provided with a line of delay and has two outputs - direct and inverse connected with a transistor key fulfilled with possibility of fulfillment of an operation "switched on" or "switched off". At that the electronic scheme is fulfilled on a digital integrated microchip. According to the second variant the interior electrode 11 of the coaxial condenser "C" is fulfilled tubular and is additionally provided with a protective shield 22. The shield 22 is fulfilled in the shape of a spiral spring out of bronze and electrically connected with the external electrode - the body 10 of the coaxial condenser "C".

EFFECT: increases sensitiveness and accuracy of measuring of the level of liquid.

6 cl, 4 dwg

FIELD: invention refers to control-measuring technique and is assigned for control and signaling about border of interface between mediums petroleum product-water in installations for purification water from petroleum products or watered petroleum products from water.

SUBSTANCE: sensor has flange, three electrodes with sleeves on their low ends filled with fresh water, moreover two of them are covered with dielectric insulation. Electrodes with sleeves are located inside tube of protective screen and are fastened in flange with aid of stuffing boxes-insulators. Screen in upper part has diaphragm ring with openings along circumference coinciding with openings in screen forming swinging compensator and is fastened to flange with aid of screws. Electrodes of sensor together with sleeves and electronic part form oscillating contour going in resonance at presence in space between electrodes of electric conductive medium (water) with following triggering of executive elements and at presence of water between electrodes of petroleum product resonance of contour stops.

EFFECT: increases reliability of work of sensor.

2 cl, 1 dwg

FIELD: physics, measurement.

SUBSTANCE: invention is related to the field of facilities for automation of different liquids level detection in industrial and household reservoirs, and also for detection of liquids availability and flow in pipelines. Method is based on application of two thermistors that have identical thermal characteristics, and includes heating of one of the thermistors by electric current and its cool-down due to heat transfer to environment, periodic measurement of voltage drop at thermistors, calculation of informative parameter, its comparison with threshold value and making decision on availability or unavailability of liquid at controlled level. At that one of thermistors is periodically heated by short pulses from power supply source. After heating is completed, ratio of non-heated and heated thermistors' voltages are repeatedly measured, and as informative parameter scaled time derivative is calculated by means of specified ratio measurement results array processing. Device for method implementation contains two thermoresistors, which are installed in sensitive element, connected to power supply source and which have temperature resistance coefficients (TRC) of the same sign and identical coefficient of heat emission in gas. Besides, it also contains analog-digital transducer and comparator, reference inlet of which is connected to source of reference signal, and outlet is connected with actuating device. Moreover, device is equipped with pulse switch and serially connected regulator of heating time and synchroniser, and also calculator of scaled derivative. For alarm on liquid flow availability, device is additionally equipped with the second comparator that is connected parallel to the first one, and the second actuating device.

EFFECT: higher efficiency of liquid level detection by increase of device actuation fast-action, reduction of power inputs and expansion of its application field.

13 cl, 3 dwg

FIELD: measuring technology.

SUBSTANCE: invention refers to a measuring device for determination of an amount d(V(z)) of conducting liquid of the conductivity LF by a capacity with vertically (z-direction) varied filling points. There is provided conductivity metre which among others has at least two electrodes extended in a z-direction. The capacitance parametres and/or the metres are ensured so that it/they can be described by means of at least one parametric function, fpi (V(z)) depending on V(z). At least one said parametric functions shall have exponential dependence on V(z). There is also described measuring element, and also method for determination of total amount of flowing liquid d (V).

EFFECT: simplified design of the device and method of measuring conductivity of the conducting liquid.

42 cl, 14 dwg

FIELD: physics.

SUBSTANCE: method if based on measuring capacitance of a double-electrode capacitive liquid level sensor, which in turn in any sequence measures capacitance of the double-electrode capacitive liquid level sensor and capacitance of the same sensor is measured after connecting a capacitive sensor of dielectric properties to it, after which the level h from the upper end of the double-electrode capacitive liquid level sensor is calculated using the formula:

, where h is the level of the liquid in the reservior; CA is capacitance of the double-electrode capacitive liquid level sensor; CB is overall capacitance of the double-electrode capacitive liquid level sensor connected in parallel to the capacitive sensor of dielectric properties; A, B and D are structural parametres of the double-electrode capacitive liquid level sensor and capacitive sensor of dielectric properties. The device for measuring liquid level has a double-electrode capacitive liquid level sensor made in form of a coaxial capacitor, and two cylindrical electrodes. The lower end of the inner electrode of the double-electrode capacitive liquid level sensor is connected to one of the electrodes of the capacitive sensor of dielectric properties through the closing contact of a reed relay, and the lower end of the outer electrode of the double-electrode liquid level sensor is connected to the second electrode of the capacitive sensor of dielectric properties.

EFFECT: high accuracy of measuring the level of different liquids, as well as elimination of measurement errors caused by change in dielectric permittivity of the measured liquid.

2 cl, 1 dwg

FIELD: physics.

SUBSTANCE: sensor for monitoring the level of a liquid has a housing and a printed-circuit board on which there is a substrate having one or two identical film resistors (thermistors) and contact pads (conductors). The printed-circuit board is in form of a plate, one short side of which is rigidly attached to the base of the housing and on the edge of the opposite free side there is a hole whose diameter is 2…4 times larger than the width of the substrate lying over the hole and made from thin heat-insulating material. Each film resistor (thermistor) is in 'point' form with dimensions in the range (0.15…0.5) mm • (0.5…0.5) mm and thickness not more than 0.0005 mm. The boundary surface between each film resistor (thermistor) and contact pads of the substrate (conductors) is in form of broken lines consisting of straight sections.

EFFECT: high mechanical strength of the structure.

3 dwg

Up!