What Is a Diaphragm Pressure Gauge, and How Does It Work?

Diaphragm pressure gauges should be a type of instrument used to measure pressure, which is different from ordinary pressure gauges. Common pressure gauges may be of the Bourdon tube type, while diaphragm types may use diaphragms to isolate the medium, preventing corrosion or high-viscosity liquids from affecting the measurement.

The diaphragm pressure gauge consists of the diaphragm, connecting components, and the dial (the internal Bourdon tube). The diaphragm acts as the sensitive element. When pressure acts on the diaphragm, it will deform. This deformation will be transmitted to the internal mechanical structure, converted into the movement of the pointer, thereby displaying the pressure value. Additionally, the diaphragm part may also have flanges or threaded connections to accommodate different installation requirements.

In terms of the working principle, it can be divided into several steps: The medium pressure acts on the diaphragm, causing the diaphragm to undergo elastic deformation, which in turn drives the connecting rod or the spring tube and other transmission mechanisms to convert the deformation into the rotation of the pointer, thereby displaying the pressure reading on the dial. It is necessary to emphasize the isolation function of the diaphragm to avoid direct contact of the measured medium with the internal mechanism. This is suitable for corrosive, high-viscosity or easily solidifying media.

Sensitive element:

The diaphragm plate is usually made of corrosion-resistant metals such as stainless steel, tantalum, or Hastelloy alloy, or non-metallic materials such as polytetrafluoroethylene (PTFE) coating. Its thickness is only 0.03 - 0.1mm, and it can undergo elastic deformation under pressure.

Isolation cavity:

The diaphragm and the instrument housing form a sealed cavity, which is filled with low-viscosity liquids such as silicone oil and fluorine oil as the pressure transmission medium. The filling liquid must have chemical inertness, a low freezing point and a high boiling point to adapt to extreme temperature environments.

Transmission mechanism:

The deformation of the diaphragm drives the linkage mechanism or capillary system inside the chamber, transmitting the displacement to the gear set, and ultimately converting it into the rotation of the dial pointer. Some models are equipped with a temperature compensation device, which can eliminate the influence of environmental temperature differences on the measurement.

Work process:

Medium pressure → Diaphragm deformation → Hydraulic filling conduction → Mechanical transmission amplification → Pointer reading

Typical application scenarios:

·Strongly corrosive media: such as sulfuric acid and liquid chlorine pipelines (tantalum material diaphragms + PTFE coating need to be selected).

·High hygiene requirements: Food-grade dairy product filling line (using polished stainless steel diaphragms to prevent microbial growth).

·High-viscosity fluid: Petroleum asphalt storage tank (equipped with capillary extension type diaphragm sealing system).

Selection Parameters：

The diaphragm pressure gauge, through its innovative isolation design, expands the boundary of pressure measurement to harshly corrosive and highly hazardous working conditions. With the development of new materials and intelligent sensing technologies, this "flexible to overcome rigid" instrument will continue to safeguard the safe and efficient operation of modern industries. Correct selection and maintenance not only extend the service life of the instrument but also provide reliable data support for production processes.