Pressure gauge and pressure detecting circuit thereof

The present invention provides a pressure detecting circuit, which is electrically connected to a coil to receive an induced electromotive force from the coil, including a movement detecting unit electrically connected to the coil to receive the induced electromotive force from the coil and find a distance of the movement of the magnetic device according to the induced electromotive force; and a converting unit electrically connected to the movement detecting unit to generate the voltage signal to indicate the distance. In addition, the present invention further provides a pressure gauge incorporated with the pressure detecting circuit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a sensor, and more particularly to a pressure gauge and a pressure detecting circuit incorporated in the pressure gauge.

2. Description of the Related Art

There are many pressure gauges, such as U-tube gauge and Bourdon-tube gauge, to measure tire pressure, atmospheric pressure, and water pressure etc.

The U-tube gauge provides water or mercury in a U-shaped tube. The surfaces of the mercury will be at the same level when the pressures on the opposite ends of the U-shaped tube are the same, and there will be a height difference between the mercury surfaces when the pressures are different. One may find the pressure according to the height difference.

A Bourdon-tube gauge has a copper alloy tube, which has an elliptical cross section and is bent into a curved shape. An end of the tube is connected to a connector. The distal end of the tube is closed, and there is a space for the tube to expand. When a pressure is transmitted to the tube through the connector, the curved tube will be extended. A link connects the distal end of the tube and a sector gear. The sector gear is provided with a pointer on a scale to show the value of pressure. In other words, the pressure may deform the tube to move the pointer through the link, and the pressure is directly proportional to the deformation of the tube that the movement of the pointer may indicate the pressure.

There are several drawbacks in the conventional pressure gauges, for example, the U-tube gauge has a poor precision in measurement, and the U-shaped tube usually is made of glass which is easy to be broken. Besides, the temperature in the U-shaped tube will affect the precision of measurement. For the Bourdon-tube gauge the temperature affects the precision of measurement also, and the material fatigue of the copper tube is another big problem.

To improve the conventional pressure gauges, a piezoelectric pressure gauge is provided. The piezoelectric pressure gauge has a piezoelectric material therein. The piezoelectric material may result in electricity from pressure that the piezoelectric pressure gauge may precisely detect pressure.

Temperature has less affection on the piezoelectric pressure gauge, and the piezoelectric pressure gauge may provide a precise measurement. However, the piezoelectric material is exposed under the pressure directly that rusting, moisture and other facts may damage the piezoelectric material. Because the piezoelectric material generates electricity that the piezoelectric pressure gauge cannot be used to sense inflammable gas. In conclusion, there still are some places in the art of pressure measurement that needs to be improved.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide a pressure gauge and a pressure detecting circuit, which may provide a precise measurement and may be applied in all fields.

According to the objective of the present invention, the present invention provides a pressure gauge for measuring a pressure of a source includes a case having a bore connecting the source; a coil, which is made of a conductor, provided in the case; a magnetic device movably received in the case; and a pressure detecting circuit electrically connected to the coil.

The magnetic device is moved by the pressure of the source that the coil generates an induced electromotive force, and the pressure detecting circuit receives the induced electromotive force to generate a voltage signal directly proportional to the induced electromotive force.

In an embodiment, the present invention further provides a pressure detecting circuit. The pressure detecting circuit is electrically connected to a coil to receive an induced electromotive force from the coil. The pressure detecting circuit includes a movement detecting unit electrically connected to the coil to receive the induced electromotive force from the coil and find a distance of the movement of the magnetic device according to the induced electromotive force; and a converting unit electrically connected to the movement detecting unit to convert the distance into the voltage signal.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1shows a pressure gauge1of the preferred embodiment of the present invention for measuring pressure of a source. The present embodiment is applied in measuring the pressure in a gas pipe100, and, however, it may be applied in any other fields. The pressure gauge1includes a case10, a coil20, a flexible film25, a magnetic device30, a spring35, and a pressure detecting circuit40.

The case10has a base11, a lid12, and a shield13. The base11has a bore111to connect the gas pipe100that gas in the gas pipe100may enter the case10via the bore111. The lid12engages the case10which has a main member121and a knob122. The main member121has a chamber121atherein and a threaded hole121b. The knob122engages the threaded hole121b. The shield13engages the lid12.

The coil20is made of a conductor, such as copper, iron, and silver. The coil20is received in the chamber121aof the lid12and surrounds the main member121.

The flexible film25is provided on an inner side of the base11to cover the bore111that the flexible film25may be expanded by the gas.

The magnetic device30is received in the chamber121aand is able to be moved relative to the coil20. The magnetic device30may be moved by the flexible film25. In the present invention, the magnetic device30is a permanent magnet, and, however, it may be an electromagnet or other members with magnetism.

The spring35is received in the chamber121awith opposite ends urging the knob122and the magnetic device30that the magnetic device30is adjustable by turning the knob122.

The gas of the gas pipe100enters the case10via the bore111and expands the flexible film25to move the magnetic device30relative to the coil20(FIG. 2). A velocity of the magnetic device30is directly proportional to the pressure of the gas. The coil20generates an induced electromotive force because of the movement of the magnetic device30, and the induced electromotive force is directly proportional to the velocity of the magnetic device30.

The pressure detecting circuit40is provided in the case10between the lid12and the shield13. The pressure detecting circuit40is electrically connected to the coil20. As shown inFIG. 3, the pressure detecting circuit40includes a movement detecting unit41, a converting unit42electrically connected to the movement detecting unit41, an adjusting unit43electrically connected to the converting unit42, and an output port44electrically connected to the adjusting unit43. The movement detecting unit41is electrically connected to coil20to receive the induced electromotive force from the coil20when the magnetic device30is moved and find a distance of the movement of the magnetic device30. In the present invention, the movement detecting unit41includes a magnetic coupling circuit411and an electromagnetic inducting circuit412to find the moving distance of the magnetic device30according to the induced electromotive force.

The converting unit42generates a voltage signal according to the result of the movement detecting unit41. The converting unit42has a filtering circuit421to filter noise, and/or unnecessary band of signal to provide a precise voltage signal.

The adjusting unit44may adjust the voltage signal from the converting unit42. In the present invention, the adjusting unit includes a multiplier431and a subtractor432to zero, fine adjust, or amplify the voltage signal.

The output port44outputs the adjusted voltage signal.

Therefore, one may get the pressure of the source according to the voltage signal from the output port44. For example, it will get a great voltage signal when the source provides a high pressure, and it will get a small voltage signal when the source provides a low pressure.

Besides, any slight movement of the magnetic device30may be detected by the electromagnetic detection that the pressure gauge may have a precise detection.

The present invention provides the flexible film25to isolate the gas of the source from the coil20, the pressure detecting circuit40, and other electronic/electric devices that these electronic/electric devices may not be damaged. Therefore, the pressure gauge1of the present invention may measure the pressure of gas, liquid, inflammable gas/liquid or any other pressure sources in all fields.

The description above is a few preferred embodiments of the present invention and the equivalence of the present invention is still in the scope of claim construction of the present invention.