Diaphragm pressure gauge

The diaphragm pressure gauge application spans from 10 mbar to 60 bar. The measuring element consists of one circular diaphragm, clamped between a pair of flanges.

The positive or negative pressure, acting on these diaphragms causes deformation of the measuring element. The magnitude of the deformation is proportional to the pressure to be measured, and it is coupled to the pointer mechanism.

Features of the diaphragm pressure gauge

SI-D100 Diaphragm pressure gauge
SI-D100 Diaphragm pressure gauge

  • Case and wetted parts from stainless steel
  • Wide choice of special materials
  • High overload safety up to the 10-fold full scale value
  • Process connection thread or open flange
  • Scale ranges from 0 … 60bar

You may like:

Diaphragm Seal Pressure/ Differential Pressure Transmitters

Submersible Pressure Transmitter for Level and Depth Measurement

Specifications of SI-D100 Diaphragm pressure gauge

Pressure gauges compliant with EN 837-3
Display ranges
0…10 mbar to 0…40 bar (unfilled)
0…60 mbar to 0…60 bar (filled)
Nominal size
100 mm
160 mm
Mechanical designStainless steel case with bayonet ring
Connections at bottom
the enlarged channel opening
in case of PTFE lining,
optional open flange
 Stainless steel
EN 837-3 accuracy
Class 1.6
Class 2.5 (with protecting foil)
Maximum pressure load
Static load
Dynamic load
 100 % of full scale values
90 % of full scale values
Up to 5-times, max. 40bar

Connection threads and materials of SI-D100 Diaphragm pressure gauge

Type 316L pressure gauges with stainless steel connection are available with a stainless steel diaphragm (40 to 250 mbar) , or a Duratherm diaphragm (0.4 to 40 bar).

In addition, they can optionally be produced with PTFE lining.

Options of SI-D100 Diaphragm pressure gauge

  • Inlet port orifice up to Ø 10 mm
  • Hygienic connection,
    • e.g. according to DIN 11851, DN 25 to DN 50,
    • with or without lateral cleaning valve
  • Other connection flanges according to former DIN standards
  • Special installation or connection orientation
  • Special scales such as dual ranges, fine-division (with knife-edge pointer) Stationary red pointer on the dial, or with external adjustment)
  • Maximum indicating pointer, external adjustment
  • Window acryl glass or polycarbonate (only for display ranges ≥ 0…100 mbar)
  • Micro-adjustable pointer, mechanism aluminum
  • Diaphragm with protection foil:
    • PTFE (> 40 mbar, vacuum tight), sealing PTFE;
    • Fine-silver (> 160 mbar, vacuum tight), sealing FPM;
    • Tantalum (> 160 mbar, vacuum tight upon request), sealing PFTE, others upon request
  • Up to 10-times overload protection, but max. 40 bar (600 psi) for measuring flange Ø 100 mm (3.94“) max. 2.5 bar (40 psi) for measuring flange Ø 160 mm (6.3“)
  • Other filling fluid, silicone oil for temp. down to -40 °C (flange sealing PTFE)
  • Version for temperatures > 100 °C
  • Electrical accessories

More Diaphragm Pressure Gauge Technical Guide

A diaphragm pressure gauge is a tool that measures the pressure of a gas or liquid by using a flexible diaphragm. The diaphragm will move in response to changes in pressure, and this movement is then translated into a reading on a dial.

These gauges are commonly used in industries like manufacturing, oil and gas, and chemical processing to monitor and control pressure in various processes. They are also commonly used in HVAC systems to measure the pressure of air and other gases.

Diaphragm pressure gauges are relatively easy to use and maintain, and they are often chosen for their accuracy, durability, and affordability. They come in different sizes, materials, and pressure ranges, making them versatile tools that can be used in a wide range of applications.

Diaphragm pressure gauge working principle
Diaphragm pressure gauge construction

A diaphragm pressure gauge is a device that uses a diaphragm with a known pressure to measure pressure in a fluid.

It has many different uses, such as monitoring the pressure of a canister of gas, measuring atmospheric pressure. Or recording the strength of the vacuum in a vacuum pump.

The diaphragm pressure gauge consists of a circular membrane, made from sheet metal of precise dimensions, which can either be flat or corrugated.

The diaphragm is mechanically connected to the transmission mechanism, which will amplify the small deflections of the diaphragm, and transfer them to the pointer.

The animation below shows the pressure gauge working principle.

You can see the movement of the diaphragm and the functioning of the transmission mechanism.

The process pressure is applied to the lower side of the diaphragm, while the upper side is at atmospheric pressure.

The differential pressure arising across the diaphragm lifts up the diaphragm and puts the pointer in motion.

The deflection of the diaphragm is very small (+/- 1 mm), making it necessary to use a high-ratio multiplying movement, to rotate the pointer along the full length of the scale.

The actuation of such a high-ratio transmission mechanism is possible, because diaphragm deflection is able to generate large forces.

Read more What is a diaphragm seal?

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Lorem ipsum dolor sit amet, consectetur adipiscing elit.

Versatility: can measure pressure of a wide range of fluids and gasesLimited range: may not be suitable for high or low pressures
Accuracy: provide precise measurementsSensitivity to overpressure: can be damaged and affect accuracy
Cost-effective: relatively affordableSusceptibility to damage: diaphragm can be damaged by certain fluids
Durability: made of durable materials and can withstand harsh conditionsEnvironmental factors: accuracy can be affected by changes in temperature, humidity, etc.

Pressure gauges with horizontal diaphragm allow to find suitable versions for even difficult kinds of media. Such as aggressive, contaminated or viscous media.

The stainless steel bayonet ring case is designed for applications, where a rust-resistant, sealed case of high chemical resistance is required (dirty damp, or corrosive atmosphere).

  • For measuring points with increased overload;
  • With liquid-filled case suitability for high dynamic pressure loads and vibrations (model 433.50);
  • For gaseous, liquid and aggressive media, also in aggressive environments;
  • With the open connecting flange option also for contaminated and viscous media;
  • Process industry:
    • Chemical, petrochemical, power plants, mining,
    • on-/offshore, environmental technology,
    • machine building and general plant construction

There are various types of pressure instruments. In addition to pressure sensors, pressure transmitters. Pressure gauges are also commonly used.

The function of a pressure gauge is to measure the pressure of fluids and gases in various industrial, commercial, and residential applications. Pressure gauges are used to monitor and regulate the pressure of liquids and gases in tanks, pipelines, and other containers to ensure that They are operating safely and efficiently.

The pressure gauge works by measuring the force that the fluid or gas exerts on a sensing element, which is typically a flexible diaphragm or a curved tube called a Bourdon tube. The sensing element then converts this force into a mechanical or electrical signal, which is displayed on the gauge as a pressure reading.

In summary, the function of a pressure gauge is to provide accurate and reliable measurements of pressure in various applications to ensure the safety and efficiency of systems and equipment.

Difference between bourdon tube and diaphragm pressure gauge

The working principle of the pressure gauge is through the elastic deformation of the sensitive element in the gauge. Then the pressure change is transmitted to the pointer by the conversion mechanism of the movement in the watch. Cause the pointer to rotate to show pressure. Sensitive element may be a Bourdon tube, diaphragm, bellows.

Therefore, the essential difference between the bourdon tube and diaphragm pressure gauge is the different sensitive components for pressure measurement.

Bourdon tube pressure gauge:
The sensitive element of the Bourdon tube is an elastic C-shaped tube bent into a circle with an oval cross-sectional area. The pressure of the measuring medium acts on the inside of the wave tube. In this way, the elliptical cross-section of the Bourdon tube will tend to be circular. Due to the slight deformation of the Bourdon tube, a certain ring stress is formed. This ring stress causes the Bourdon tube to extend outward. Since the head of the elastic Bourdon tube is not fixed, it will deform slightly. The amount of deformation depends on the pressure of the measuring medium. The deformation of the Bourdon tube displays the pressure of the measured medium indirectly by the pointer through the movement.

Diaphragm pressure gauge:
The sensitive element of the Diaphragm is composed of two membranes with circular waves connected together. The pressure of the measuring medium acts on the inside of the capsule cavity. The resulting deformation can be used to indirectly measure the pressure of the medium. The pressure value is indicated by the pointer. The capsule pressure gauge is generally used to measure the pressure of the gas, and it can also measure the micro-pressure and over-pressure protection to a certain extent. When several bellows sensitive components are stacked together, a large transmission force will be generated to measure very small pressure.

Bourdon tubes have the following advantages over diaphragm elements:

  • They cover small pressure ranges from 0 to 0.6 bar up to high pressure ranges from 0 to 10,000 bar.
  • They enable accuracies up to class 0.1 of the calibration regulations.
  • They are easier to manufacture.
  • They can easily be connected or sealed with the pressurised components. Depending on the material and pressure load, they are either soldered, welded or screwed to them.

Diaphragm pressure gauges are used when a Bourdon tube pressure gauge reaches its limits.

Extended reading: Pressure indicator transmitters


In a pressure gauge, a diaphragm is a flexible membrane that responds to changes in pressure by expanding or contracting. The movement of the diaphragm is then converted into a reading on the gauge, which displays the pressure of the fluid or gas being measured.

Diaphragms can be made from a variety of materials, such as stainless steel or synthetic materials like rubber or silicone. They are designed to be durable and withstand the pressure and conditions of the environment in which they are used.

The capsule pressure gauge is also called micro pressure gauge. It is suitable for measuring the low micro-pressure of liquid, gas or steam which has no explosion risk, no crystallization, no solidification, and corrosive effect on copper and copper alloys.
The capsule pressure gauge uses the capsule as a sensitive element for measuring small pressures. Measure the micro-pressure and negative pressure of the corrosive effect on the copper alloy, no explosion hazard gas. Widely used in boiler ventilation, gas pipeline, combustion device and other similar equipment.

In the pressure gauge, the pressure measured by the diaphragm is generally regarded as relative pressure. Generally, the relative point is selected as atmospheric pressure. The elastic deformation of the diaphragm under the pressure of the medium. Amplified by the gear transmission mechanism of the pressure gauge. The pressure gauge will show the relative value to the atmospheric pressure (either high or low).

There are several different types of pressure gauges that are commonly used in different applications:

Bourdon Tube Pressure Gauge: This type of gauge uses a curved tube that is attached to the gauge mechanism. As the pressure of the fluid or gas being measured increases, the tube straightens out, causing the gauge mechanism to move and display the pressure reading.

Diaphragm Pressure Gauge: As we discussed earlier, diaphragm pressure gauges use a flexible membrane that responds to changes in pressure by expanding or contracting. This movement is then converted into a reading on the gauge.

Differential Pressure Gauge: This type of gauge measures the difference in pressure between two points in a system. It consists of two pressure inputs and a gauge mechanism that calculates the difference between the two inputs.

Digital Pressure Gauge: This type of gauge uses electronic sensors to measure pressure and displays the reading on a digital screen.

Compound Pressure Gauge: This type of gauge can measure both positive and negative pressures. It uses two Bourdon tubes, one for positive pressure and one for negative pressure, to display the reading on the gauge.

Overall, the type of pressure gauge used will depend on the specific application and requirements. Each type of gauge has its own advantages and disadvantages, and it’s important to choose the right one for the job.

More pressure measurements and applications

Sino-Instrument offers over 50 Diaphragm pressure gauge products.

About 50% of these are Diaphragm pressure gauge, 40% are Differential Pressure Gauge, and 40% are Diaphragm Seal Pressure transmitters.

A wide variety of  Diaphragm pressure gauge options are available to you, such as free samples, paid samples. 

Sino-Instrument is a globally recognized supplier and manufacturer of Diaphragm pressure gauge, located in China.

The top supplying country is China (Mainland), which supply 100% of Diaphragm pressure gauge respectively.

Sino-Instrument sells through a mature distribution network that reaches all 50 states and 30 countries worldwide. Diaphragm pressure gauge products are most popular in Domestic Market, Southeast Asia, and Mid East. 

You can ensure product safety by selecting from certified suppliers, with ISO9001, ISO14001 certification.

Request a Quote