CN2243068Y

CN2243068Y - Gas mass flow meter

Info

Publication number: CN2243068Y
Application number: CN 96209897
Authority: CN
Inventors: 应为忠; 李然
Original assignee: Shengye Science & Tech Development Co ltd Beijing
Current assignee: Shengye Science & Tech Development Co ltd Beijing
Priority date: 1996-05-10
Filing date: 1996-05-10
Publication date: 1996-12-18
Anticipated expiration: 2006-05-10

Abstract

The utility model relates to a gas mass flow meter. The utility model is characterized in that the utility model adopts a structure in a divided flow type; the utility model is provided with three winding type temperature transducers which are arranged on a capillary pipe; the middle winding is a heating coil and two side windings which are symmetric are heat sensitive material coils. According to temperature difference which is generated when gas molecule flows through the capillary pipe, the utility model outputs resistance difference; through an electricity converting circuit, the utility model outputs standard signals to achieve measurement and the digital display of gaseous mass flow rate.

Description

Mass-flow gas meter

The utility model is a kind of gas measurement device, particularly a kind of device of direct measurement gas mass rate.

Existing mass-flow gas meter is generally the measurement volume, and then compensates according to the atmospheric pressure at scene and temperature and to be converted into gas mass flow, and major defect is: 1. have pressure and temperature measuring error and conversion error; 2. mass rate shows hysteresis, the mass rate of pilot-gas in real time

The purpose of this utility model is at above-mentioned shortcoming, directly adopt temperature sensor, according to the caloric receptivity of gas molecule and the corresponding relation of thermal discharge and gas mass flow, the electric quantity signal of outputting standard, numeral display standard state (0 ℃, the 101.325KPa) gas mass flow under.

The purpose of this utility model realizes in the following way: there is a restrictor (2) matrix (1) inside in hollow, on matrix (1) top is kapillary winding type temperature sensor (3), described sensor (3) is made up of a capillary (4) and three groups of coils twining on it, middle winding is Camas heating collar (5), two surveys winding symmetrical, that resistance equates is thermo-sensitive material coil (6), coil (6) links to each other with power conversion circuit, and power conversion circuit comprises signal processing circuit, interface circuit and digital display circuit.

The utility model is owing to adopting restrictor to become shunting structure, can satisfy the measurement requirement of the gas flow of arbitrary range, and adopt the interface shape of power conversion circuit and international standard standard, make it to possess that volume is little, precision is high, the advantage of highly versatile.

Fig. 1 is mass-flow gas meter shunting structure figure.

Fig. 2 is the sensor wiring diagram.

Fig. 3 is the sensor output characteristics.

Fig. 4 is the power conversion circuit block diagram.

In the drawings: (1) matrix; (2) restrictor; (3) sensor; (4) kapillary; (5) Camas heater coil; (6) thermo-sensitive material coil; (7) amplifier; (8) linear compensation; (9) lead network; (10) interface circuit; (11) digital indicator.

Below in conjunction with accompanying drawing the utility model is described specifically:

Energized, Camas heater coil (5) reaches uniform temperature, when not having gas flow in kapillary (4), the resistance of the thermo-sensitive material coil (6) of two groups of symmetries equates, when gas flows in kapillary (4), changed the thermal equilibrium of two thermo-sensitive material coils, the resistance of two coils is changed, and the proportional relation of mass rate of its resistance extent and gas is passed through power conversion circuit, the voltage of outputting standard or current signal carry out numeral and show.

Because two groups of coils of thermo-sensitive material are to adopt identical temperature-coefficient of electrical resistance, and resistance is equal and symmetrical, and when variation of ambient temperature, the resistance of two coils still equates so be not subjected to the influence of environment temperature, to have the characteristic of automatic zero set (AZS).

For the specific heat of the mixed gas of single component and fixed proportion, in 0～60 ℃ of scope a constant, what of the suction of gas molecule, thermal discharge and gas molecule are proportional, promptly with the proportional relation of the mass rate of gas, with pressure independent.

Use the direct measurement gas mass rate of kapillary to be through type, be applicable to the measurement and the control of small gas flow, because the output characteristics of sensor (Fig. 3) is parabola shaped, after the flow of gas surpasses linearity range, the signal of output increases with gas flow and reduces, for guaranteeing that the interior gas flow of kapillary (4) is in the linearity range scope of output signal, adopt restrictor and form the shunting structure (see figure 1), gas flow in the kapillary becomes fixed proportion with the gas flow in the main channel, select different shunting ratios, the range that different gas mass flows will be arranged, thereby shunting structure can satisfy the measurement requirement of the gas flow of arbitrary range.

The effect of restrictor (2) is to produce certain pressure reduction, gas can be shunted enter in the kapillary, and the structure of restrictor (2) can adopt powder metallurgy, woven wire, aperture plate, minim gap diaphragm etc.

The effect of power conversion circuit is that the resistance difference signal with the proportional relation of gas mass flow is converted to the voltage millivolt signal through Hui Dengsi electric bridge (not drawing among the figure).

The effect of signal processing circuit is that voltage signal is done two kinds of processing respectively after twice amplification, at first utilize a lead network (9) to make processed voltage signal be proportional to transducing signal, its objective is the time lag that solves sensor, secondly the common mode voltage of amplifying signal is introduced sensor bridge circuit non-linear with the compensation sensor dynamic response, thereby greatly guaranteed and improved the precision of flow measurement.

The interface shape of the standard of adopting international standards, and in circuit, carried out standard signal output simultaneously and handled, current signal output: 4～20mA, 0～20mA; Voltage signal: 0～5V, 1～5V.Be characterized in the precision height, stability is strong, carrying load ability is strong, is applicable to the distant signal transmission, interface circuit is characterised in that flow measurement, control and outputting standard Signal Processing carry out simultaneously.

Claims

1. mass-flow gas meter, it is characterized in that: there is a restrictor (2) matrix (1) inside in hollow, on matrix (1) top is kapillary winding type temperature sensor (3), described sensor (3) is made up of a capillary (4) and three groups of coils twining on it, middle winding is Camas heating collar (5), two surveys winding symmetrical, that resistance equates is thermo-sensitive material coil (6), coil (6) links to each other with power conversion circuit, and power conversion circuit comprises signal processing circuit, interface circuit and digital display circuit.