SU662815A1

SU662815A1 - Capacitance-type level gauge

Info

Publication number: SU662815A1
Application number: SU772453154A
Authority: SU
Inventors: Николай Михайлович Курносов; Гарри Захарович Солганик; Аркадий Иванович Троегубов
Original assignee: Государственный научно-исследовательский институт теплоэнергетического приборостроения
Priority date: 1977-02-15
Filing date: 1977-02-15
Publication date: 1979-05-15

Description

(54) ЕМКОСТНОЙ УРОВНЕМЕР(54) CAPACITY LEVEL

1one

Изобретение относитс к области приборостроени и может быть использовано дл измерени уровн различных жидкостей.The invention relates to the field of instrumentation and can be used to measure the level of various liquids.

Известен емкостной уровнемер, содержащий измерительный и компенсационный емкостные датчики, операционный усилитель, преобразователь емкости в напр жение и генератор тактовых импульсов 1.A capacitive level gauge is known, comprising measuring and compensating capacitive sensors, an operational amplifier, a capacitance-to-voltage converter, and a clock pulse generator 1.

Наиболее близким по технической сущности к предложенному вл етс емкостной уровнемер, содержащий измерительный и компенсационный датчики, тактовый генератор , преобразователь «емкость-врем , с подключенным к нему измерительным датчиком , устройство посто нной задержки, включенные через последовательно соединенные схему НЕ-И и детектор среднего значени на вход дифференциального усилител 2.The closest in technical essence to the proposed is a capacitive level gauge containing measuring and compensating sensors, a clock generator, a capacitance-time converter, with a measuring sensor connected to it, a constant delay device connected through a series-connected non-AND circuit and a medium detector values to the input of the differential amplifier 2.

Однако устройство обладает низкой точностью измерени уровн сред с малыми величинами диэлектрической проницаемости при значительном изменении их электрофизических характеристик в процессе эксплуатации .However, the device has a low accuracy of measuring the level of media with low dielectric constant values with a significant change in their electrical characteristics during operation.

Цель изобретени - увеличение точности измерени сред с малой величиной диэлектрической проницаемости.The purpose of the invention is to increase the accuracy of measuring media with a low dielectric constant.

Это достигаетс тем, что емкостной уровнемер снабжен преобразователем «емкостьнапр жение-врем , подключенным к компенсационному датчику, и преобразователем «напр жение-врем , выходы которых через последовательно соединенные дополнительные схему НЕ-И и детектор подключены к инвертирующему входу усилител , а выход усилител соединен с управл ющими входами преобразователей «емкость-напр жениеврем и «напр жение-врем .This is achieved by the fact that the capacitive level gauge is equipped with a capacitance voltage-time converter connected to a compensation sensor and a voltage-time converter, the outputs of which are connected through the series-connected additional AND-I circuit and the detector are connected to the inverting input of the amplifier, and the amplifier output is connected with the control inputs of the capacitance-voltage time and voltage-time converters.

На чертеже представлена функциональна схема емкостного уровнемера:The drawing shows a functional diagram of a capacitive level gauge:

Claims

The device includes a clock generator 1, a capacitor-time 2 converter with a measuring part of sensor 2a connected to it, a constant delay device 3, a capacitor-voltage-time converter 4 with a compensation part of sensor 4a, a voltage-converter 5, non-AND 6 and 7 circuits, average value detectors 8 and 9, and operational amplifier 10 with two inputs. The output of the generator 1 is connected to the converting inputs of the converters "capacitance 2," capacitance-voltage-time 4, "voltage-time 5 n of the device 3 of constant delay. One of the inputs of the device NOT-6 is connected to the output of the capacitor-time 2 converter, and the second to the output of the device 3 of a constant delay. The output of the NAND circuit is connected to the input of the average value detector 8, the output of which is connected to one of the inputs of the operational amplifier 10. The outputs of the converters 4 and 5 are connected to two inputs of the NAND circuit 7. The input of this circuit is connected to the average value detector 9, the output of which is connected to the second input of the operational amplifier 10. The output of the amplifier 10 is connected to the control inputs of the converters 4 and 5. The device operates as follows. The converter 2 converts the capacitance of the measuring part into the duration of the time interval, which in the non-AND 6 circuit is compared with the duration of the time interval of the constant delay device 3. The average value detector 8 converts the pulse duration at the output of the NANDI 6 circuit into a proportional DC voltage. The length of the time interval of the converter 4 is determined by the capacitance of the compensation part of the sensor 4a, which is located below the measuring part 2a and therefore depends only on the dielectric constant of the medium and the value of the output voltage of the level gauge. The duration of the time interval of the converter 5 is determined by the magnitude of the output voltage of the level gauge. Devices 7 and 9 operate similarly to the non-AND 6 schemes and the average value detector 8, respectively. At the initial moment, i.e., in the absence of liquid in the measuring part of the sensor, the duration of the time interval of the converter 2 is equal to the duration of the time interval of the device 3 constant delay. The duration of the differential pulse at the output of the circuit is NOT-AND 6 and the voltage at the output of the detector 8 are equal to zero. The voltage at the output of the level gauge is zero, and therefore the duration of the time intervals of the transducers 4 and 5 is zero. and the duration of the time interval of the converter 2. A difference pulse appears at the output of the NAND AND 6 circuit. This pulse is converted by the detector 8 into a DC voltage and fed to the input of the amplifier 10, so that the output voltage appears, with an increase in which the duration of the time intervals of converters 4 and 5 increases. But the rate of increase of the duration of converter 4 in (the dielectric constant of the medium being measured) times exceeds the rate of increase of the duration of time interval of converter 5, so that the output of the circuit is NOT -And a differential pulse appears, which is converted by the detector 9 into a constant voltage and fed to the second (counterbalancing) input of the amplifier 10, trying to be compared in magnitude with the voltage at the first input. The input voltage of the amplifier 10 linearly depends on the level and does not depend on the dielectric constant of the liquid. Claims of Invention A capacitive level gauge comprising measuring and compensating sensors, a clock generator, a capacitance-time converter connected to a measuring sensor, and a constant delay device connected through a series-connected NOT-I circuit and a mean value detector to the input of a differential amplifier, differing in that, in order to increase the accuracy of measuring media with a low dielectric constant, it is equipped with a capacitance-time-to-transducer connected to a voltage sensor and a voltage-time converter, the outputs of which are connected via a series-connected additional NOT-I circuit and the detector are connected to the inverting input of the amplifier, and the output of the amplifier is connected to the control inputs of the capacitors-voltage-time and voltage converters time Sources of information taken into account during the examination 1. USSR author's certificate No. 435459, cl. G 01 F 23/26, 1972.

2. Institute works, NIITeplopribor, No. 79, 1972, p. 35-37.