JPS6139603B2 - - Google Patents

Description

[Detailed Description of the Invention] Various types of water level meters (wave height meters) have been used to more accurately capture wave phenomena and water level changes in hydraulic model experiments and the like. They are used differently depending on the purpose, type, and measurement accuracy of the experiment, but there are many examples in which hydraulic water level gauges are used.

In large-scale hydraulic models, water level changes are small, so it is necessary to measure with higher precision. Recently, water level gauges that measure water level on the water surface are often used.In the case of this type of water level gauge, if the pedestal becomes an obstacle and cannot be installed, a water pressure type water level gauge that places the detector directly on the bottom of the water can be used. Is required. In this case, it must have the same accuracy as a water level meter that measures at the water surface, such as a stylus type water level meter or a resistance line water level meter. In addition, when performing long-term measurements,
You will need something that has low drift and is highly waterproof. In the case of a water pressure type, the measurement range changes depending on the pressure-receiving area, so it is best to use a small and thin disc-shaped type that has high sensitivity in a small area as possible.
Additionally, since it will be installed on the bottom of the hydraulic model, it must be able to be installed easily even on uneven surfaces.

There are three types of conventional hydraulic water level gauges, including those for field surveys:

(1) A method of directly receiving pressure fluctuations on a pressure receiving surface and converting the strain into an electrical quantity to measure it. (2) A method of converting changes in water pressure into changes in air pressure and measuring temperature changes due to that air pressure. (3) ) There is a method of converting changes in water pressure into air pressure and directly measuring this air pressure.

Among these, type (1) above is suitable for micro-pressure measurements that require particularly high accuracy for hydraulic models, and is suitable for use as a hydraulic water level gauge in shallow water depth locations with little fluctuation. This is the only method. In cases (2) and (3), it is theoretically difficult to achieve high accuracy because air pressure fluctuations are replaced by bellows changes and the amount of change is extracted using a potentiometer.

In view of the above, the water level detector of the present invention captures the amount of water level change as the amount of water pressure change, and uses a resistance wire strain gauge to directly convert and measure this into an electrical quantity.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings. As shown in FIGS. 1 and 2, the detector main body 1 includes a ring-shaped base 2, a diaphragm 3 on the top surface, and a waterproof cover 4 on the bottom surface. By fixing the diaphragm 3 in a watertight manner, a waterproof chamber 5 is formed therein, and within this waterproof chamber 5, a balance ring 6 adhesively fixed to the inner surface of the diaphragm 3,
Four extremely thin strain plates 7 fixed to the inner surface of the base body 2 at equal intervals on the circumference and protruding inward are connected to the transmission pin 8.
are connected by.

Each of the strain plates 7 has a structure shown in FIGS.
As can be seen from the figure, strain gauges 9a, 9b, 9c and 9d (resistance wire strain gauges) are glued alternately on the front and back sides, and these strain gauges 9a
~9d are connected to form a Whiston bridge, as shown in FIG. has been done.

In addition, the inside of the waterproof chamber 5 is opened to the atmosphere by connecting a conduit pipe 12 that reaches above the water surface to a pipe connection port 11 in order to avoid measurement errors due to the pressure inside the chamber. .

When the minute water level detector having the above configuration is placed at the bottom of a hydraulic model, etc. as shown in FIG. , and a bending displacement is applied from the balance ring 6 to the strain plate 7 via the transmission pin 8 . The bending stress generated in the strain plate 7 is proportional to the water level, and can be determined by the change ΔE in the output voltage based on the resistance change ΔR of the strain gauges 9a to 9d bonded to each strain plate. That is, the resistance change ΔR produced by the four sets of strain gauges 9a to 9d is obtained by the Whiston bridge shown in FIG. 5, and a corresponding output voltage change ΔE is generated. Therefore, as shown in FIG. 4, by guiding the output obtained from the detector body 1 to the recorder 14 via the amplifier 13, the minute water level sensed as a minute water pressure by the diaphragm can be converted into an electrical output. It can then be recorded.

The balance ring 6 is used to collect water pressure fluctuations received on the pressure receiving surface and effectively and evenly transmit them to the strain gauge, and is necessary to maintain balance.

In addition, each strain gauge has its own characteristics depending on tension and bending, and installing four strain gauges on the same side of the strain plate is likely to cause errors, so strain gauges are placed alternately on the front and back of the strain plate in advance. By installing it, it is possible to detect accurate values.

Furthermore, since the waterproof chamber 5 is opened to the atmosphere through the conduit pipe 12 connected to the pipe connection port 11, the diaphragm is displaced purely due to changes in the water level.
Pressure errors caused by temperature expansion of internal air can be eliminated.

The conventional water pressure type mentioned above uses a bellows in the detection part and detects the amount of water level change from changes in air pressure, which is affected by temperature changes and is not suitable for detecting minute water levels. The amount of water required required a large detector, and it was impossible to install a large-scale hydraulic model due to the shallow depth of the water. On the other hand, the major features of the minute water level detector of the present invention detailed above include the following.

(1) As a hydraulic water level meter, it can measure minute water levels with high accuracy.

(2) It is extremely easy to install and can be set up in any location.

(3) Little drift due to changes in water quality and temperature.

(4) Since it is a hydraulic type, short period waves such as noise components can be removed.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway plan view of the water level detector main body of the present invention, Fig. 2 is a side sectional view thereof, Fig. 3 is a side sectional view of the main part showing the state in which the diaphragm is displaced, and Fig. 4 is the state in use. Figure 5 is a circuit diagram of the Whiston bridge. 1...Detector body, 2...Base, 3...Diaphragm, 4...Waterproof cover, 5...Waterproof chamber, 6...
...Balance ring, 7...Strain plate, 8...Transmission pin, 9a-9d...Strain gauge, 10...
Captire cord, 11...Pipe connection port, 1
2... Conduit pipe.

Claims (1)

[Claims] 1. A diaphragm is fixed to the top surface of the base to form a waterproof chamber within the base, and within this waterproof chamber, a balance ring fixed to the inner surface of the diaphragm and a balance ring fixed to the inner surface of the base at equal circumferential intervals are placed inward. The four protruding strain plates are connected by a transmission pin, resistance wire strain gauges are alternately glued to the front and back sides of each strain plate, and the wires are connected to form a Whiston bridge. A minute water level detector characterized in that the waterproof chamber is opened to the atmosphere through an introduction pipe connected to a pipe connection port.