JPH03274453A - Magnetic oxygen meter - Google Patents

Abstract

PURPOSE:To enhance the utilization factor of magnetic flux and to enhance measuring accuracy by small magnetic flux by allowing the purge gas blown into measuring gas from the central part of a magnetic field forming means to flow so as to cross the total magnetic flux. CONSTITUTION:The measuring gas Sg flowing into a space 2a from an introducing port 10a passes through holes 3a, 3b to be equally divided to flow to the spaces of the slots 4a, 4b of a plate 4 and receives the effect of the magnetic fields due to pole pieces 40a, 40b on the side of the slot 4a but no effect of the magnetic fields on the side of the slot 4b. The purge gas Pg entering from an introducing port 20c is equally branched into grooves 20d and the branched gases respectively pass through thermistors 60a, 60b to flow through holes 5a, 5b into the spaces of the slots 4a, 4b. Since the gas Sg is not attracted to magnetic fields when no oxygen is contained in the gas Sg, there is no difference between the flow velocities of the branched gases Pg and, since the gas Sg is sucked in the hole 3a when the concn. of oxygen in the gas Sg is high, the outflow of the gas Pg on the sides of the pole pieces 40a, 40b becomes bad and difference is generated in a flow dividing ratio. The flow velocities are detected by the thermistors 60a, 60b and the difference between the flow velocities is operated to detect the concn. of oxygen gas.

Description

[Detailed description of the invention] [Industrial application field] The present invention is used to detect the oxygen gas concentration in a measurement gas.

The present invention relates to a magnetic oxygen meter that detects the oxygen gas concentration in a measurement gas by utilizing the magnetic properties of oxygen gas.

〔overview〕

The present invention is a magnetic oxygen meter that detects the concentration of oxygen gas in a measurement gas using the magnetic properties of oxygen gas, in which purge gas is blown into the measurement gas from the center of the magnetic field forming means, and the purge gas crosses the total magnetic flux. By stacking multiple plate materials so that they flow together, the system improves the efficiency of magnetic flux utilization, increases sensitivity to oxygen concentration, and improves measurement accuracy.

[Conventional technology]

Conventionally, magnetic oxygen meters have been developed in Japanese Patent Laid-Open No. 64, which utilizes the property that the magnetic susceptibility of oxygen gas is higher than that of other gases.
-6753, and those disclosed in Japanese Unexamined Patent Publication No. 1-167653. An example of this is shown in FIG. 15, in which measurement gas Sg has an inlet 11b1, an outlet 11c1, a bypass pipe 11d1 provided at an intermediate position between the inlet 11b and the outlet 11c, and a nearly flat donut-shaped measurement. A measurement chamber 11 constituted by a passage 11a and a measurement passage 1
a magnetic field forming means for forming a magnetic field Mf in a direction substantially perpendicular to the measurement passage 11a in a part of the measurement gas passing through the measurement passage 1a;
A pair of detection means 12a, 12b are provided in the bypass pipe 11d at symmetrical positions across the purge gas supply port 14 which supplies purge gas Pg from a purge gas supply means (not shown), and detect the purge gas flow.
Comparing means includes constant resistance circuits 13a, 13b and a subtraction circuit 13C, which measure changes in the passing gas flow based on changes in the resistance value of 2b, and output these differences as an oxygen gas concentration signal in the measurement gas Sg. There is one with 13.

This device allows measurement gas Sg to flow into the measurement chamber 11,
The purge gas Pg is introduced from the purge gas supply port 14, and the bypass pipe 11 (divided into two parts at I) is connected to the two connecting parts 15a.
, 15b into the measurement chamber 11. A magnetic field Mf is formed only in one of the two connecting portions 15a. Oxygen gas is attracted by this magnetic field Mf, and is prevented from flowing into the measurement chamber 11 at the connection portion 15a. That is, the higher the oxygen concentration in the measurement gas Sg, the more the two connections 15a
, 15b becomes unbalanced. This is detected as an electrical signal by the two detection means 12a112b, and the comparison means 13 compares the electrical signals.

[Problem to be solved by the invention]

In the conventional magnetic oxygen meter using the split flow ratio method described above, purge gas is introduced from one side of the magnetic field forming means, and the back pressure generated when this purge gas pushes out the oxygen gas present in the magnetic field causes the split flow to occur due to the concentration difference in oxygen gas. The ratio is extracted as a signal, and since the purge gas flow path is narrow with a bypass pipe, the utilization efficiency of magnetic flux is poor, and since a strong magnetic flux is required, the magnetic field forming means must be large. There are drawbacks.

The present invention aims to eliminate these drawbacks, and aims to provide a magnetic oximeter that can improve the efficiency of magnetic flux utilization and improve measurement accuracy with a small magnetic flux.

[Means to solve the problem]

The present invention provides a substantially flat space provided with a measurement gas inlet and an outlet thereof, and a magnetic field forming means for forming a magnetic field in a part of the measurement gas passing through this space, and the effects of this magnetic field are different. purge gas supply means for supplying purge gas into the space from two holes provided at two positions, two detection means for respectively detecting the flow rates of the purge gas supplied to the two holes, and The present invention is characterized by comprising a comparison means for comparing detection outputs.

The flat space and the purge gas supply means are formed by overlapping a plurality of plate materials, and the plate material is disk-shaped, and the inlet port and the outlet port are arranged on a meridian passing through the center of one of the disks. Preferably, the two holes are formed at symmetrical positions across the meridian.

[Effect]

Since the magnetic susceptibility of oxygen gas is higher than that of other gases, it is strongly attracted to the magnetic field, causing a change in the split flow ratio of the purge gas that flows in branches, resulting in a difference in the detection outputs detected by the pair of detection means. A comparison means compares and outputs the difference between the detection outputs.

In the magnetic oximeter of the present invention, when gas flows through a flat passage, it is divided into equal amounts, and one of the branched gas flows crosses all of the total magnetic flux of the magnetic field formed by the magnetic field forming means. flows.

This makes it possible to increase the efficiency of magnetic flux utilization and the sensitivity to oxygen concentration. Furthermore, since the purge gas outlet hole on the measurement side and the purge gas outlet hole on the comparison side can be placed close to each other in the flat space, the flow of the measurement gas in the vicinity of the two holes is equal, making it possible to reduce angular errors. can.

〔Example〕

Next, embodiments of the present invention will be described based on the drawings.

FIG. 1 is a diagram showing the overall configuration of an embodiment of the present invention, FIG. 2 is a plan view of the embodiment of the present invention, FIG. 3 is a sectional view taken along line A-A in FIG. 2 of the embodiment of the present invention, and FIG. A bottom view of the embodiment of the present invention,
FIG. 5 is a sectional view taken along line BB in FIG. 2 of the embodiment of the present invention;
6 to 10 are plan views of each plate laminated in the embodiment of the present invention, FIG. 11 is a partially sectional perspective view of the embodiment of the present invention in an assembled state, and FIG. 12 is an external appearance of the embodiment of the present invention. FIG.

In the embodiment of the present invention, the measurement gas Sg inlet 10a'J6
The base 10 is provided with a purge gas Pg and its discharge port 10b, and the cover 20 is provided with an inlet port 20c for purge gas Pg.
a substantially flat space formed inside; a magnetic field forming means including pole pieces 40a, 4[]b and a magnet 50 that forms a magnetic field in a part of the measurement gas Sg passing through this space; purge gas supply means for supplying purge gas Pg into the space from two holes provided at two positions with different effects; and two detection means for respectively detecting the flow rate of purge gas Pg supplied to the two holes. Thermistor 60a, 60b
and a comparison means 13 including constant resistance circuits 13a, 13b and a subtraction circuit 13c for comparing the detection outputs of the two thermistors 60a and 60b.

The flat space and the purge gas supply means are formed by stacking a plurality of plate materials, each of which has a disk shape, and has inlets 10a, 20c and an outlet 10b.
is on a meridian passing through one center of this disk, and the two holes are formed at symmetrical positions across this meridian.

That is, as shown in FIGS. 2 to 11, the base 10
The holes 1a shown in FIG. 6 are formed in the space formed when the cover 20 is assembled in order from the base 10 side.

1b with a thickness of 0.4 mm, a donut-shaped plate 2 with a thickness of 0.8 mm having a space 2a shown in FIG. 7, and a plate 2 with a thickness of 0.4 mm having holes 3a and 3b shown in FIG.
mm plate 3, long hole 4a shown in FIG.

4b and the hole 5a shown in FIG.
, 5b with a thickness of 0.4 mm are sandwiched in a stacked state.

As described above, the base 10 is provided with an inlet 10a for the measurement gas Sg and an outlet 1o1 for the exhaust gas, and a vibrator is welded (brazed) to the inlet 10a and the outlet 10b, respectively. Furthermore, a pole piece 40b for guiding the magnetic flux from the magnet 50 is fitted.

The cover 20 has an inlet 20C for introducing purge gas Pg.
Holes 20 in which two thermistors 60a and 60b are buried
a, 20b, and a ring-shaped groove 20d are provided, and the pole piece 40a is fitted into the base 10 at a position corresponding to the pole piece 40b. Inlet port 20
A vibrator is welded (brazed) to c like the base IO. The unnecessary portion of the groove 20d is filled with a rubber part 90 as shown in FIG.

The pole pieces 40a and 40b are made of materials with high magnetic permeability, such as 535C and pure iron.These materials have poor corrosion resistance, and in order to prevent them from coming into direct contact with the measurement gas, they are made of materials such as 535C and pure iron. The surface is sealed by ring 70a. This seal is 01J 70
It can also be done by welding (brazing) without using a. Also, pole piece 40a.

A depression is provided in the center corresponding to 40b in order not to waste magnetic flux.

Since the measurement gas Sg often contains corrosive gas components, the parts in contact with the gas are required to be corrosion resistant. Further, in order to allow as much magnetic flux as possible to pass through the measurement gas 3g, it is preferable that the magnetic permeability is close to 1. 5US is the material for the gas flow path that satisfies these conditions.
316 is mainly used. However, it is difficult to machine elongated gas channels with high precision using difficult-to-machine materials such as S U 3316, so holes of various shapes are made in a thin plate of 5US 316 and the holes are overlapped to create the optimal flow channel. The present invention is characterized in that it is formed.

H-410 (7) Measurement gas Sg flows in through the inlet 10a, and exhaust gas flows out through the exhaust port 10b. The holes 1a and lb of the plate 1 are inlets and outlets for the measurement gas, and are used to prevent the measurement gas sg from coming into direct contact with the pole piece 40b. The donut-shaped space 2a of the plate 2 forms a measurement gas SgO flow path. The holes 3a and 3b of the plate 3 are outlets for the purge gas Pg, and the hole 3a is located at the center of the pole piece 40a140b. Two long holes 4a and 4b in the plate 4 form a space for guiding the purge gas Pg to the center of the magnet. The plate 5 is used to prevent the pole piece 40a on the cover 20 side from coming into contact with gas, and since it is normally in contact with only the purge gas Pg, it may be very thin, for example, Q, about 1 mm.

Purge gas Pg is introduced from the inlet 20C of the cover 20, split into two directions through the groove 20d, and the flow rate ratio of the split purge gas Pg is measured by the measurement thermistor 60a160b.

The cover 20 and the base 10 are fixed with screws 80, and
It is completely sealed from the outside air by the ring 70b.

In the assembled state as shown in FIG. 12, the pole pieces 40a and 40b are connected by the magnet 50.
are sandwiched and a magnetic field is formed.

Next, the operation of the embodiment of the present invention configured as described above will be explained. FIG. 13 and FIG. 14 are diagrams explaining the flow of gas in the embodiment of the present invention.

The measurement gas Sg flows into the space 2a of the plate 2 from the inlet 10a of the base 10, and enters the holes 3a and 3b of the plate 3.
, and an equal amount is divided into the spaces of the elongated holes 4a and 4b of the plate 4. The measurement gas Sg diverted to the long hole 4a side is influenced by the magnetic field by the poles and pieces 40a and 40b, and the measurement gas Sg diverted to the long hole 4b side is not affected by the magnetic field.

On the other hand, the purge gas Pg enters the groove 20 ( ) from the inlet 20 c of the cover 20 and branches into equal amounts to the left and right to the thermistor 60.
a and 60b respectively, and pass through the hole 5a of the plate 5.
and 5b to the space between the elongated holes 4a and 4b of the plate 4. The exhaust gas passes through the hole 1a of the plate 1 communicating with the space 2a of the plate 2, and is discharged from the outlet 10b of the base.

In this way, the flow rates of the measurement gas Sg and purge gas Pg are divided equally between the space affected by the magnetic field and the space not affected by the magnetic field, and the purge gas Pg divides the total magnetic flux in the space affected by the magnetic field. The flow rate is measured.

If oxygen gas is not included in the measurement gas Sg in such a branched flow, the oxygen gas is not attracted to the magnetic field and there is no difference in the flow rate between the two divided flows of the purge gas Pg. On the other hand, when the oxygen gas concentration in the measurement gas Sg is high, the measurement gas is drawn into the hole 3a of the plate 3, which is the outlet on the pole piece 40a and 4Ob side of the purge gas Pg, making it difficult for the purge gas Pg to flow. As a result, the purge gas P on the pole pieces 40a and 40b side
g decreases, and a difference occurs in the split flow ratio. These flow velocities are detected by thermistors 60a and 60b, respectively, and the detected a signals are output from the constant resistance circuits 13a and 1 of the comparison means 13.
3b, and a subtraction circuit 13c calculates the difference between the two flow velocities.

〔Effect of the invention〕

As described above, according to the present invention, the purge gas flows through the entire magnetic flux of the magnetic pole piece, so that the sensitivity to oxygen concentration is increased.

In other words, highly accurate measurements can be made using small magnets.

Furthermore, since the purge gas outlet holes on the measurement side and the comparison side are close to each other, angular errors can be reduced. Furthermore, since it can be constructed by overlapping thin plates, processing is simple and production costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the overall configuration of an embodiment of the present invention. FIG. 2 is a plan view of an embodiment of the present invention. FIG. 3 is a sectional view taken along line AA in FIG. 2 of the embodiment of the present invention. FIG. 4 is a bottom view of the embodiment of the present invention. FIG. 5 is a sectional view taken along line BB in FIG. 2 of the embodiment of the present invention. 6 to 10 are plan views of various plates used in embodiments of the present invention. FIG. 11 is a partially sectional perspective view of the embodiment of the present invention in an assembled state. FIG. 12 is a perspective view showing the appearance of an embodiment of the present invention. FIG. 13 and FIG. 14 are diagrams explaining the flow of gas in the embodiment of the present invention. FIG. 15 is a diagram showing the configuration of a conventional example. 1.2.3.4.5...B1/-t, 10...Base, 10a, llb, 20c = inlet, l[
lb, IIC-...Exhaust port, 11...Measurement chamber, ll
a...Measurement passage, lld...Bypass pipe, 12a
, 12b--detecting means, 13--comparing means, 13a
, 13b...constant resistance circuit, 13c...subtraction circuit,
14...Purge gas supply port, 15a, 15b-...
Connection part, 20-...Cover, 20d...L 40a
, 40b...Pole piece, 50...Magnet, 60a, 60b...Thermistor.

Claims (1)

[Claims] 1. A substantially flat space provided with an inlet and an outlet for measuring gas; magnetic field forming means for forming a magnetic field in a portion of the measuring gas passing through this space; and this magnetic field. purge gas supply means for supplying purge gas into the space from two holes provided at two positions with different effects; two detection means for respectively detecting the flow rates of the purge gas supplied to the two holes; A magnetic oxygen meter characterized by comprising a comparison means for comparing detection outputs of two detection means. 2. The magnetic oximeter according to claim 1, wherein the flat space and the purge gas supply means are formed by stacking a plurality of plate materials. 3. The plate material is disk-shaped, the inlet port and the outlet port are on a meridian passing through one center of the disk, and the two holes are formed at symmetrical positions through this meridian line. The magnetic oxygen meter according to item 1.