JPS60185119A - Heat sensitive flow-rate detector - Google Patents

Abstract

PURPOSE:To make it possible to measure the flow rate of fluid highly accurately without relation to the temperature of the fluid to be measured, by setting the difference in temperatures of a heating resistor and a temperature compensating resistor so that the temperature difference has the proportional relationship with the temperature of the fluid. CONSTITUTION:A resistor 6 is made to be a heat sensitive resistor having the same temperature coefficient as those of a heating resistor 2 and a temperature compensating resistor 5. The resistors are provided in a flow path of fluid so that the temperatures of the resistors 2 and 6 become the same value. Based on the balancing conditions of a bridge circuit, the difference in temperatures of the resistors 2 and 5 has the proportional relationship with the temperature of the resistor 2. The current flowing resistor 2 does not depend on the temperature of the fluid. As a result, a voltage V11 at an output terminal 11 does not depend on the temperature of the fluid, and it is expressed as a function of the fluid. Therefore, the exact flow speed can be obtained by measuring the voltage V11.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention uses a heat-sensitive flow detection device 11 to detect the flow rate of a flowing fluid by utilizing heat transfer between a heating element and a flowing fluid. The present invention relates to a flow rate detection device 6.

[Prior art]

The configuration of a conventional device of this type is shown in FIG. 1.) In this figure, (1) is a DC IL1. source, (211:j-subject+
II! A heating resistor disposed in a flow path of a flowing fluid, which is a constant IC body, is used to maintain a temperature of [This is a dependent resistor. +31 is a fixed resistor connected in series with the above heat generating resistor, (4) is a transistor connected in series with the above heat generating resistor, treated as fC, and passing current to the above heat generating resistor +21. It is for supplying.

In addition, (51 is a Yl-6 degree compensation resistor arranged in the flow path of the flowing fluid, which corresponds to the upper d pi brother thermal resistor)
;2) 0 t(il +71 are fixed resistors, respectively.2) The above-mentioned heating resistor (21, temperature compensation resistor (51, and fixed resistor 131 +61 (71ij) -, these are configured to form a bridge circuit.

(8) is an amplifier, and its non-inverting input terminal (8A) is
7 heating resistor (21) is connected to the connection point (9) of the fixed resistor (3), 9 inverted input car Mizuko (8B) is connected to the identification resistor (6) and (7), l light point t11vc: I & connection In addition, the output V1M child (scull:
It is connected to the base of the transistor (4).

(lυ is the output signal 1"r1M terminal, and the bridge circuit 1
This is to detect the "lower forward pressure" state at t.

Now, the resistor 121131 +01 that constitutes the bridge circuit
+61 +71 each J) (J-1; anti-1) 1j-
Let R2,R,, 'R5,R6,R, and incandescent resistance (2
), and if the resistance temperature coefficient of resistance 15) using α1 and 11 is α), the thermal resistance (2) and ζ＾A degrees fli ・
The lit resistance (5) is as follows.

■(2-R2o(1+αT2) −-il+R5=R5
o(1+αT5) −=−= +2 square R2o;
Resistance value R5o of resistor (2) at 0°C; Resistance value T2 of resistor (51) at 0°C; Temperature T5 of resistor (2); Temperature of resistor (5) 〇Also, the slave side conditions of the above bridge circuit is R2・R, = R3 (R5 medium length,) ・・・・・・・・・
- Since (3), the following equation can be obtained from the il+-U equation.

)... (4) Here, T=T2-T5.

Also, if each resistor is selected so that RA ``'5O-R7'' is 20 in formula 41, the coefficient of T5 becomes 0 and becomes 9.
711A of heating resistor (21) and temperature compensation resistor (5)
Ii difference △T is.

By the way, it is generally known that the following relationship holds between the calorific value P of the heating element in the fluid and the flow velocity U.

P-work2R2-(a+1), /i)△T...
・ ・ ・ ・ (51 \ ＼, engine, current A L B; (2) is a constant determined by the physical properties of fluids.

Therefore, if ΔT is constant as described above, the calorific value P becomes a linear function of the square root of the flow velocity.

Since the pressure v11 at the output terminal 11110' in FIG. 1 is given by, by measuring this vl, cAt
It was designed to detect the ML speed of a moving object.

7J) According to the conventional constant temperature difference measurement method such as Shikojino, v, 1 = Miyaru R2 is I? Because it has a 4 degree dependence, it has not been possible to perform temperature-compensated, high-resolution measurements over a wide range of l'1', IX degrees and t1α.

[Kaimei no 41 Etsumi] This supercapacitor was made in order to eliminate such drawbacks, and is configured so that the temperature difference between the heating resistor (1) and the temperature compensator (1) is proportional to the fluid temperature. [Embodiment of the Invention] Hereinafter, an embodiment of the present invention shown in FIG. 2 will be described.

It is clear from this figure that the conventional equipment [d resistor +61 t-heating resistor +21 and temperature compensation resistor 51]
In addition, the connection point (9) is replaced with a temperature-sensitive resistor having the same resistance temperature coefficient as the output terminal (lυ), and the other configurations are the same as the conventional device shown in FIG.

The operation in such a configuration will be explained.

First, the temperature sensitive resistance (6) is expressed as follows.

R=RN+αT) 16) 6 60 ＼ and R6o is the temperature of the resistance (resistance value T6 of 61; resistance 16) at 0°C.

Note that the resistance value of 1 heating resistor (21) is sufficiently smaller than that of R5 and R6.

Each of them shall be installed in the flow path of the fluid so that the temperature of the heat generating resistor (2) and the l function of the temperature sensitive resistor (61) are always equal.

Since the bridge circuit is shown in formula 131, ill 12111i1 formula and T2 = 1/4 of T6.
By substituting each of ' in equation (3), RA'''50ΔT=T2(R3・R5o+R3・R6o
-R7・R2o)--y(R, -R2o-R, -R6o
-R,・Fl,. )-=-171. However, △T
=T2-T5.

+1) If the V valley body resistance is selected so that RA"50 = R7"20, the temperature difference ΔT between T5 and T2 will be as follows...C.

18) As is clear from the formula, l! The anchor IJ difference ΔT of the Korurao resistance (21 and Takido f+i compensating resistance 15) is the heating resistance I
'liA has a proportional relationship with T2.

(8) From Equation (8) and (5), heating resistance +z+ +c = flow rate is expressed as follows (tThis is expressed in a form that does not depend on the fluid temperature). Subtracting v and 1 gives the following 0 However, C1 and C2 are constants.

In other words, vl does not depend on the fluid temperature and is expressed as a function of flow velocity, so by measuring vll, an accurate flow velocity can be determined. (1) [Effects of the Invention] This invention Because the iC is configured as above.

0, which allows accurate measurement of fluid flow regardless of the temperature of the fluid being measured.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a 10M configuration of a conventional device, and FIG. 2 is a schematic diagram showing an embodiment of the present invention. In the figure, (21 is a heating resistor, (4) is a transistor, 15
) is the temperature compensation resistor, (61 is the temperature sensitive resistor, (8) is the increase [
1] “Instrument, (Ill is the output terminal. The same symbols indicate the corresponding parts. Agent: Masuhata Oiwa (and 2 others)

Claims (1)

[Claims] il+ A temperature-dependent heating resistor installed in a fluid flow path and heated by a suppressed peeking flow, and a temperature-compensating resistor whose resistance changes depending on the temperature V of the fluid. Construct a bridge circuit including the above bridge circuit q month 1 pressure I + ll to measure the flow rate of the fluid V divided into the above heating resistor and the above 1 current resistance 11X resistor A heat-sensitive flow characterized in that the temperature difference is proportional to the temperature of the fluid. 7t fl out-'&
'1m: 0 (2) Claim 5, characterized in that the heating resistor and the 1!1A degree compensating resistor have the same resistance temperature coefficient.
44141't N self-discipline thermal type mouse detection device. t: 31 The bridge circuit consists of one heat-generating resistor ((, the series connection of the resistance for temperature curve III and the temperature-sensitive resistor, ν including the body on the other side?j: 'P:j Royal request for a government 1.
Flood 1711 first filler tA second, IQ-described heat-sensitive flow rate detection device 1ffi. (4) The temperature-sensitive resistor is installed in the fluid flow path.
3rd Nogai Bodhisattva included in the range of % d as a sign) Kango-shaped waste detection device