JPH01311231A - Mass flowmeter - Google Patents

Abstract

PURPOSE:To measure a flow rate with fast response by supplying two resistance bodies so that magnetic fields produced around the resistance bodies are opposite in direction from the flowing direction of fluid. CONSTITUTION:The resistance bodies 2u and 2d are self-heating type heat- sensing coils which are wound around a conduit 1 independently at a proper intervals in the opposite directions. Then the currents Iu and Id are supplied to the resistance bodies 2u and 2d so that the magnetic fields phiu and phid produced around the resistance bodies 2u and 2d are opposite in direction from the direction of the fluid flowing in the conduit 1. Consequently, an output signal which has an extremely low noise level is obtained. Thus, an output which has small voltage variation and an extremely low noise level is obtained without using any noise filter and the flow rate is measured with fast response.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a mass flow meter in which two resistors are independently wound around a conduit through which a fluid flows.

[Conventional technology]

In the above mass flow meter, two resistors are independently wound around the conduit through which the fluid flows, and in order to keep the temperature of both paper antibodies constant, a current is supplied to each of the paper antibodies. The mass flow rate of fluid flowing through the conduit is determined based on the difference in power supplied to the conduit.

[Problem to be solved by the invention]

However, in the past, since the direction of the current flowing through the resistor was not clearly defined, the output signal had a high noise level due to mutual electromagnetic induction between the resistors.
In other words, only an output signal with a poor S/N ratio was obtained. In order to reduce the noise to a level that does not pose a practical problem as a mass flow meter, it is possible to install a noise filter in the signal processing section, but this will impair the response, which would otherwise require high precision and high speed response. This was a major obstacle in obtaining a mass flow meter.

The present invention has been made with the above-mentioned considerations in mind, and an object of the present invention is to provide a mass flow meter that can obtain an output signal free from noise effects and has high-speed response.

[Means to solve the problem]

In order to achieve the above-mentioned object, the mass flow meter according to the present invention is configured such that the direction of the magnetic field generated in each of the two resistors wound around the conduit through which the fluid flows is opposite to the direction in which the fluid flows. A current is caused to flow through each of the resistors.

[Effect]

According to the above configuration, current is caused to flow through each of the resistors so that the direction of the magnetic field generated in each of the two resistors wound around the conduit through which the fluid flows is opposite to the direction of the fluid. , it is possible to obtain an output signal free from the influence of noise without using a noise filter, and therefore, the flow rate can be measured with high speed response, so that the above object is completely achieved.

【Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of the configuration of a mass meter according to the present invention. In the figure, reference numeral 1 denotes a conduit through which a fluid F flows, and the fluid F flows in the direction of the arrow.

2u and 2d are two self-heating thermosensitive coils (hereinafter referred to as resistors 2u and 2d) which are wound independently of each other at appropriate intervals on the outer periphery of the conduit 1 in opposite directions and independently from each other. The first resistor 2u and the second resistor 2d, which are referred to as a resistor 2d, are made of a temperature-sensitive resistance wire with a large temperature coefficient, such as an iron-nickel alloy, and are The sensor is configured to detect even such changes.

3.4 is a constant temperature control circuit including a first resistor 2u and a second resistor 2d as constituent elements of bridge circuits 8 and 14, which will be described later, respectively. (hereinafter referred to as the first constant temperature control circuit 3 and the second constant temperature control circuit 4), these first constant temperature control circuits 3
The second constant temperature control circuit 4 is composed of the same components, and controls so that the temperatures of the first resistor 2u and the second resistor 2d are always equal to each other at a predetermined temperature.

That is, the first constant temperature control circuit 3 includes a first resistor 2u, a temperature setting resistor 5 of the first resistor 2u, and a bridge resistor 6.7.
A bridge circuit 8 and a control circuit 9 are provided. Further, the second constant temperature control circuit 4 includes a second resistor 2d, a temperature setting resistor 10 of the second resistor 2d, and a bridge resistor 1.
1.12 and a variable resistor 13, and a control circuit 15. The variable resistor 13 is used to adjust the outputs of the bridge circuits 8 and 14 to be equal to each other when the flow rate of the fluid F in the conduit 1 is zero. Also, resistance 5. 6. 7.10.1
1.12.13 has a sufficiently small temperature coefficient compared to the first resistor 2u and the second resistor 2d.

The first resistor 2u and the second resistor 2d are the first resistor 2u and the second resistor 2d.
Magnetic fields Φ1., which are generated in the first resistor 2u and the second resistor 2d, respectively, due to the flow of currents ru and r supplied by the constant temperature control circuit 3 and the second constant temperature control circuit 4, respectively. Connect them to the first constant temperature control circuit 3 and the second constant temperature control circuit 4, respectively, so that the direction of Φ4 is opposite to the direction of the fluid F flowing in the conduit l (see FIG. 2 (A)). be.

16 and 17 are an addition circuit and a subtraction circuit, respectively, and the potentials P, , P outputted to the output points 18 and 19 of the bridge circuit 8 and 14 are respectively input, and the former 16 outputs p and +p as addition outputs. The latter 17 outputs PI-Pt as a subtracted output. 20 is a division circuit, which inputs the outputs from the addition circuit 24 and the subtraction circuit, and outputs (PI-Px)/(P+) as the division output.
+Pt) is output. And this output (Pt −
Pg )/(P, +Pz) is proportional to the mass flow rate of fluid F flowing in conduit 1, so by multiplying this by an appropriate constant, the mass flow rate of fluid F flowing in conduit 1 can be obtained. be able to. Note that 21 is an output terminal.

In the mass flow meter having the above configuration, the magnetic field Φ is generated in each of the two resistors 2u and 2d wound around the conduit 1. , Φ4 is in the opposite direction to the direction of the fluid F flowing in the conduit l, so that the current flows through the resistor 2u+2d! ,,
! , it is possible to obtain an output signal K with an extremely low noise level, as shown in FIG. 3(A). Therefore, unlike conventional mass flow meters,
Even without using a noise filter, it is possible to obtain an output with small voltage fluctuations and an extremely low noise level, so flow rate measurement can be performed with high-speed response.

Now, to explain about Figs. 2 and 3, Figs. 2 (A) to (D) show the current flowing through the two resistors 2u and 2d. . ,! 4, the current supply direction and the current! , , each resistor 2u, 2 by Ia
The magnetic fields Φ1.d and Φ1. The direction of Φ4 and the direction of the fluid F flowing inside the conduit l are shown, among which (B) to (
D) shows a comparative example, and FIGS. 3(A) to (D) show the second
Figures (A) to (D) are waveform diagrams showing temporal changes in the output signal in each case, of which (B) to (D) show comparative examples. From these diagrams, it can be seen that noise It can be seen that the level is extremely high.

The present invention is not limited to the above-described embodiments, and, for example, the resistors 2u and 2d may be wound around the conduit 1 in a direction other than the illustrated side.

As 2d, an indirectly heated angry coil may be used.

〔Effect of the invention〕

As explained above, in the mass flow meter according to the present invention, each of the resistors is arranged such that the direction of the magnetic field generated in each of the two resistors wound around the conduit through which the fluid flows is opposite to the direction in which the fluid flows. Since a current is passed through the flow rate, the flow rate can be measured with high accuracy and high-speed response.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a mass flow meter according to an embodiment of the present invention. Figures 2 (A) to (D) show the direction of current supply when current is supplied to two resistors, the direction of the magnetic field generated in each resistor by the current, and the direction of fluid flowing in the conduit. An explanatory diagram showing the
) is a waveform diagram showing temporal changes in the output signal. 1... Conduit, 2u, 2d... Resistor, F... Fluid, ■. . ■4...Current, Φ1. Φ4...Magnetic field. Applicant: Rihito Aesthetics Co., Ltd.
Patent attorney Hideo Itomoto (A) (C) Figure 2 (B) (D) u Id (A) (C) Figure 3 (B) (D)

Claims (1)

[Claims] In a mass flow meter in which two resistors are independently wound around a conduit through which a fluid flows, each of the resistors is arranged such that the direction of the magnetic field generated in each of the two resistors is opposite to the direction in which the fluid flows. A mass flow meter characterized by allowing current to flow through it.