SU920496A2

SU920496A2 - Detector of thermal conductivity with pyroelectric

Info

Publication number: SU920496A2
Application number: SU792733764A
Authority: SU
Inventors: Анатолий Андреевич Балаухин; Борис Григорьевич Второв; Георгий Владимирович Гугля; Гомес Де Сегура Уррако Агустин; Владимир Ильич Калмановский; Валерий Владимирович Шевченко
Original assignee: Предприятие П/Я В-8644
Priority date: 1979-03-05
Filing date: 1979-03-05
Publication date: 1982-04-15

Description

II

Изобретение относитс к газовой хроматографии.This invention relates to gas chromatography.

По основному авт.св. № 721723 известен детектор теплопроводности с пироэлектриком дл газовой хроматографии . Это устройство содержит корпус с измерительной и сравнительной камерой, нагреватель, пироэлёктрики противоположной пол ризации в качестве чувствительных элементов , каждый изкоторых одной из своих плоскостей, перпендикул рных направлению пол ризации, имеет электрический и тепловой контакт с корпусом нагревател , а другой плоскостью , параллельной первой, имеет тепловой контакт с корпусом детектора через слой анализируемого газаОAccording to the main auth. No. 721723 is a known thermal conductivity detector with pyroelectric for gas chromatography. This device contains a housing with a measuring and comparative chamber, a heater, and opposite polarization pyroelectrics as sensitive elements, each of which one of its planes perpendicular to the polarization direction has electrical and thermal contact with the heater body, and the other parallel to the first, has thermal contact with the detector body through the layer of the analyzed gas

Известный детектор характеризуетс непосредственным тепловым контактом пироэлектриков с корпусом нагревател , что ограничивает чувствительность детектора.The known detector is characterized by direct thermal contact of the pyroelectrics with the heater body, which limits the sensitivity of the detector.

Цель изобретени - повышение чувствительности детектора.The purpose of the invention is to increase the sensitivity of the detector.

Указанна цель достигаетс тем, что плоскости пироэлектриков, наход щиес в тепловом контакте с корпусом нагревател , отделены от него слоем газа.This goal is achieved by the fact that the planes of pyroelectrics, which are in thermal contact with the heater body, are separated from it by a layer of gas.

На чертеже представлена конструкци детектора.The drawing shows the design of the detector.

Claims

In the massive brass case of the detector 10, necessary to reduce the effect of temperature changes in the detector thermostat, a heater 2 is placed, consisting of a nichrome spiral placed in a ceramic box and a special steel screen 3, necessary to increase the heat capacity of the heater. Two identical pyroelectrics of opposite polarization k are located symmetrically on both sides of the heater, separated from the heater and the housing by gaps, but have electrical contact with them. The difference signal is removed from the opposite njlock system (measuring electrodes) of pyroelectrics using high-resistance leads to pickup signal 5 and fed to the input of amplifier 6. For sealing, gaskets of heat-resistant rubber and aluminum are used. and goes out through the tube 9. The detector works as follows. In the steady state, when streams of pure carrier gas flowing through the input tubes for gas flows 8 flow through the detector channels, the temperature of the surfaces of the measuring electrodes of the pyroelectric k is equal and determined by the temperature of the thermostating and the power dissipated by the heater 2. the required temperature difference between the heater 2 and the housing 1, and the average temperature of the pyroelectrics t, which ensures the maximum sensitivity of the detector at a given temperature, t temperature controlled. Electric signals of pyroelectrics, coming through high-resistance leads 5 to the input of amplifier 6, are equal in magnitude and opposite in sign. The difference signal of the detector is zero. When passing through one channel together with the carrier gas of any component of the split mixture, which has more or less thermal conductivity, the temperature of the measuring surface of one of the pyroelectrics changes by a certain amount, which causes a change in the electrical signal by an amount proportional to the amount of the analyte. The detector signal is proportional to the temperature difference of the housing-heater and the rate of change of temperature, which is determined, in particular, by the heat capacity of the sensing element. In a known detector, the maximum heater temperature is determined by the maximum temperature of the pyroelectric, which in turn is determined by the Curie point and cannot be greater than a certain maximum value (). In the proposed design, where the heater and the sensing element are disconnected, the temperature of the heater can be increased, which leads to an increase in sensitivity. At the same time, the presence of an additional gap also leads to an additional sensitivity increase and due to an increase in the rate of change in the average temperature of the pyro, electrician, due to a change in the temperature gradient in the gap when the thermal conductivity of the gas changes in a charge (ore). ceteris paribus, it is all the more so as the heat capacity of the sensing element is smaller. In a known detector, the heat capacity is determined by the sum of the heat capacities of the pyroelectric In the proposed construction, it is only the heat capacity of the pyroelectric that, in turn, leads to an additional increase in sensitivity. At the same time, this also leads to a decrease in inertia, which also improves the performance characteristics of the detector.Profelectric detector with ff 721723 It is also distinguished by the fact that, in order to increase its sensitivity, the plane of pyroelectrics, which are in thermal contact with the heater, is separated from it by a layer of gas. Sources of information taken into account during the examination 1. USSR author's certificate No. 721723, cl. G 01 N 25/18 (prototype). (according to W 25 11 + 9/25)