The method of determining the level of liquid media and device for its implementation
(57) Abstract:The essence of the invention: control object placed thermoresistive Converter in the form of three series-connected resistive sensing elements (SE) measurement and compensation, of different length and with different resistances. Measure the voltage drop across re, whose values are used to calculate the desired value level. Previously in the same conditions of heat transfer for all SE determine the normalizing coefficients, which eliminates calibration. Thermoresistive the Converter is implemented in the form of cables with mineral insulation. Current and potential conclusions SE form with them a U-shaped electrical branch with a loop-like arrangement of the conductors in the connection. thermocouple is connected to the measuring circuit. 2 S. p. f-crystals, 1 Il. The invention relates to measuring technique and can be used for level measurement of liquids in chemical, power, metallurgical and other industries.A known method of measuring the liquid level thermal sensor that uses the difference in conditions of heat exchange between podogrevaemyj are converters with resistive sensors. At the same time to reduce the influence of measurement conditions (medium, pressure, temperature) on the readings of the sensor is also sensitive measuring element, use one or two helper.In the known method level value is calculated by the ratio of the two difference signals determined by the resistances of the two auxiliary and sensitive measuring elements, all three thermoresistive element have equal resistance and flow the same current.To implement the method requires the equality of all three sensing elements, which requires them to customize and create a measuring transducer or three times longer than the measurement range, or very complex designs.Closest to the claimed method according to technical essence is a way of determining the level of liquid media, including accommodation in the testing object thermoresistive Converter in the form of three series-connected resistive sensing elements measuring and compensation, of different length and with different resistances in different conditions of heat transfer and the measurement of the fall is fast device, containing thermoresistive Converter with three sensors connected with their current and potential conclusions respectively to the power unit and computing unit (2).The disadvantage of this method is the need to pregraduate sensor when changing from one liquid medium to another, or when the difference of the physical properties of the resistive elements of gauges of different parties.A disadvantage of the known device is that you cannot use for a variety of liquids in a wide range of temperatures and pressures.The technical result produced by the invention is to improve accuracy in the measurement of any liquid medium in a wide range of temperatures and pressures.This result is achieved in that in the known method pre-measure the voltage drop Uè0U10U20on the sensitive elements in the same conditions of heat transfer, determine the correction coefficients Kand, K1, K2as the ratio of the voltage drop across any of the sensing elements to the voltage drop across the corresponding sensitive element, and the value of urosticte specified result in the known device for determining the level of liquid media sensitive resistive elements are placed within the cable mineral insulated metal sheath, hermetically closed at one end, current and potential conclusions sensitive elements withdrawn from the sheath of the cable with its other end with the formation together with sensors installed along the cable, U-shaped electrical branch contacts which, in the points of connection of all conductors, formed by the loops of the latter.The drawing schematically shows a device for determining the level.The device comprises a cable thermoresistive level Converter comprising a sealed metal shell 1 is made of stainless steel, the current findings 2, potential findings 3, compacted electrically insulating and thermally conductive powder 4 from magnesium oxide, sensitive measuring element (SE) 5, compensatory SE 6, 7 of the single core conductor, made for example from alumel or Nickel. To ensure high reliability of cable thermocouple level during operation all communication between the SE and outputs generated by loop-like arrangement of conductors. The end of the transducer immersed in the measuring environment, hermetically sealed, and current and potential findings go in the same direction, forming a U-shaped electric is Artie not shown).The measuring circuit consists of power supply, switch, ADC and computing unit indicator.Resistance measurement and compensation (SE) are determined by the particular dimensions of the measurement objects and measurement range of the level.To determine the level carry out the normalization of the signals of the three SE in the same conditions of heat exchange, for which cable thermocouple placed horizontally in the water, air, oil, etc. thus determine the relationship of the voltage drop across each of the three SE on any of these voltage drops, taken as a measure for rationing, for example, compensatory SE 7, always in fluid U20. Then normalizing (correction) coefficients are equal to, respectively:
< / BR>In computing the block all signals from the measuring SE 5 are multiplied by the Kandand with compensatory SE 6, which is located in the gas (vapor phase) - K1, K21.Normalization eliminates the influence on the measurement results of the differences in the length, cross-section and the resistance of the sensitive element, which take place in the manufacture of the level Converter.Further, in the computing unit is CC>1U2Uandthe current values of the voltage drop across the compensating and measuring SE.Of the invention allow the measurement level for almost any object and the measurement conditions, without prior calibration.Cable run resistive thermal Converter allows to obtain a monolithic structure, small size (diameter 5-7 mm), tough enough to withstand high pressures (up to 40 MPa), and flexible enough to be located in almost any object made of materials capable of operating at temperatures from -200 to +1000oC.The use of compressed powdered material with high thermal conductivity between the SE and the protective sheath and the small size of thermocouple can significantly reduce thermal resistance between the SE and the medium, and this allows to increase the temperature difference between the parts of the measuring sensitive element located in the liquid and in the gas, and consequently to improve the accuracy and robustness. In addition, the small size and good thermal conductivity between the SE and the medium improves the dynamic properties of the Converter.Accommodation all vintagee hole. 1. The method of determining the level of liquid media, including accommodation in the testing object thermoresistive Converter in the form of three series-connected resistive sensing elements measuring and compensation, of different length and with different resistances, and measuring the voltage drop UandU1U2on the sensitive items in different conditions of heat exchange, wherein the pre-measure the voltage drop Uand0U10U20on the sensitive elements in the same conditions of heat transfer, determine the correction coefficients Kand, K1, K2as the ratio of the voltage drop across any of the sensing elements to the voltage drop across the corresponding sensitive element, and the level value determined by the formula
< / BR>where L is the length measuring sensor element.2. Device for determining the level of liquid media containing thermoresistive Converter in the form of three resistive sensing elements of different lengths and different resistance compensation and placed between the measuring connected in series and podkluchitsa fact, that sensitive resistive elements are placed within the cable mineral insulated metal sheath which is sealed at one end, current and potential conclusions sensitive elements withdrawn from the sheath of the cable with its other end with the formation together with sensors installed along the cable, U-shaped electrical branch, the contacts of which are at the points of connection of all conductors are formed by loops of the latter.
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.
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.
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.
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.
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
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
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.