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

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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

Diaphragm pressure gauge working principle

Diaphragm pressure gauge working principle
Diaphragm pressure gauge working principle

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?

Applications of the diaphragm pressure gauge

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

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


What is capsule pressure gauge?

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.

How does a diaphragm pressure gauge work?

Diaphragm pressure gauge consists of a diaphragm isolator and a universal pressure gauge to form a system pressure gauge. The spring tube is evacuated by special equipment. And fill people with irrigation fluid. Seal it with a diaphragm. When the pressure P of the measured medium acts on the diaphragm, it deforms. The working fluid filled in the compression system makes the working fluid form a △ P equivalent to P, with the help of work. The conduction of the liquid causes a corresponding elastic deformation-displacement at the free end of the elastic element (spring tube) in the pressure meter. According to the working principle of the pressure instrument matched with it, the measured pressure value is displayed.

What does diaphragm measure?

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)

What are the different types of pressure gauges?

1. Pressure gauges can be divided into precision pressure gauges and general pressure gauges according to their measurement accuracy. The measurement accuracy grades of precision pressure gauges are 0.1, 0.16, 0.25, 0.4 and 0.05 respectively. The measurement accuracy levels of general pressure gauges are 1.0, 1.6, 2.5, and 4.0, respectively.
2. Pressure gauges are divided into: general pressure gauges, absolute pressure gauges, and differential pressure gauges according to their indicated pressure standards. The general pressure gauge is based on atmospheric pressure. The absolute pressure gauge is based on the absolute zero pressure. The differential pressure gauge measures the difference between the two measured pressures.
3. The pressure gauge is divided into: vacuum gauge, pressure vacuum gauge, micro pressure gauge, low pressure gauge, medium pressure gauge and high pressure gauge according to its measuring range. Vacuum gauges are used to measure pressure values ​​less than atmospheric pressure. Pressure vacuum gauges are used to measure pressure values ​​less than and greater than atmospheric pressure. The micro pressure gauge is used to measure the pressure value less than 60,000 Pa. The low pressure gauge is used to measure the pressure value of 0 ~ 6MPa. The medium pressure gauge is used to measure the pressure value of 10 ~ 60MPa. The high pressure meter is used to measure the pressure value above 100MPa.
4. The pressure gauge is divided according to its display mode: pointer pressure gauge, digital pressure gauge.
5. Pressure gauges are divided according to their use functions: pressure gauges can be divided into local indication type pressure gauges and live signal control type pressure gauges according to their different use functions.
6. Specially measured pressure gauge. General pressure gauges, vacuum pressure gauges, shock-resistant pressure gauges, stainless steel pressure gauges, etc. are all on-site indicating pressure gauges, and have no other control functions except for indicating pressure.
-The shell of the shockproof pressure gauge is made into a fully sealed structure. And the damping oil is filled in the shell (mostly filled with silicone oil now). Because of its damping effect, it can be used in the measurement place of working environment vibration or medium pressure (load) pulsation.
-The pressure gauge with electric contact control switch can realize the alarm or control function.
-A pressure gauge with a remote transmission mechanism can provide electrical signals (such as resistance signals or standard DC current signals) required in industrial engineering.
-The isolator (chemical seal) used in the diaphragm meter can isolate the measured medium from the instrument through the isolation diaphragm. In order to measure the pressure of strong corrosion, high temperature, easy to crystallize medium.

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.

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