What Is a Compound Gauge?
Compound gauges are pressure gauges that can measure both positive and negative pressures.
In addition to compound gauges, there are also ordinary pressure gauges and vacuum gauges, each of which can measure different pressures. Commonly used pressure gauges can measure only positive pressure, while vacuum gauges can measure only negative pressure.
Compound gauges can measure both positive and negative pressure, but the range of pressure they can measure is limited to -0.1 to 0.4 MPaG.
Applications of Compound Gauges
Compound gauges are used in places where the operating conditions of a machine can result in either positive or negative pressure.
Examples include places where pumps are used to draw gases or liquids, or equipment that use steam for heat exchange. When pumps are used to draw in gases or liquids, the pressure inside the pump may be lower than atmospheric pressure, so it is better to use compound gauges.
Compound gauges are often used for industrial purposes, but they are also used in familiar places, such as installed in the water supply side piping of fire pump trucks.
Principle of Compound Gauges
When pressure is applied to compound gauges, the “Bourdon tube” inside the pressure gauge is deformed. The pressure applied is detected from the degree of deformation, and the pressure is measured by reflecting the detected value as it is.
When negative pressure is measured with a compound gauges, it is not possible to say that the negative pressure is accurately measured because it is indicated by detecting the deformation of the Bourdon tube in the opposite direction. If you want to know the exact value of negative pressure, it is better to use a vacuum gauge even if the negative pressure is very small.
In addition, an increasing number of compound gauges are nowadays digitally marked. Digital readings are easier to understand at a glance than scale readings, and the accuracy is so high that they can be used for inspections at public institutions.