Principle of Operation of Pressure Gauges and Areas of Application

Manometers are compact mechanical devices that measure pressure indicators. Different modifications of such instruments allow them to work with liquids or gases, including steam and air.

Measuring pressure with such devices is necessary in various fields, including water and gas pipelines, heating boilers and compressors, autoclaves, compressed gas cylinders (including pneumatic rifles). Most of these devices are universal: they can be designed to measure different indicators: excess or differential pressure, atmospheric pressure, and can also be used as vacuum gauges.

Types of Manometers

Wherever pressure levels need to be monitored, the installation of such devices is necessary. Otherwise, violations of technological processes are inevitable, which in turn can provoke a critical situation. There are 7 groups of manometers depending on the expected operating conditions.

Reference Manometers

• For checking measuring equipment (other manometers).
• Operate with minimal error in various media.
• Accuracy class – from 0.05 to 0.2.

Electric Contact

• Provide control and warning about reaching a critical level of destructive load.
• Operate with a built-in electric network control mechanism: upon reaching critical loads, they turn off equipment or release pressure to a safe level through a valve.
• Can be used in liquid and gaseous media.

General Technical

• Can be used in non-freezing environments.
• Have good vibration resistance.
• Mounted on transport and heating systems.
• Accuracy class – 1.0-2.5.

Self-recording

• Provide visual monitoring of the system status as well as recording indicators.
• Record data in the form of a diagram, which allows tracking pressure levels dynamically.
• Primarily used in food industry enterprises and thermal power plants.

Special

• For working with special gases (e.g., ammonia, argon)
• Produced in colored cases, which allows distinguishing them from other devices.
• Accuracy class – from 1.0 to 2.5.

Railway

• For mechanisms servicing rail electric transport.
• Characterized by increased vibration resistance.
• Constant mechanical impact on the case does not distort the obtained data.

Marine

• Supplied in a case protected from external influences and atmospheric precipitation.
• Can be installed not only on ships but also on outdoor gas distributors.
• Suitable for liquid and gaseous media.

Application Areas of Manometers

Manometers differ not only by area of use but also by the type of mechanism for measuring pressure indicators in the medium. Five standard groups of devices are distinguished here.

Electric Contact

• Suitable for automatic pressure control and regulation systems.
• The device design is based on two movable pointers that need to be set to minimum and maximum allowable values.
• When one of the limit values is reached, the electric circuit closes, and the control panel receives a signal to release pressure or shut down the system.

Liquid-filled

• Operate on the physical principle of communicating vessels.
• Used to measure pressure in a liquid column.
• Work in contact with a liquid medium, which often causes contamination and inaccurate measurements.
• Nowadays, they are used less frequently.

Spring

• The most popular devices with a simple and reliable design.
• Can measure within the range of 0.1-4000 Bar.
• The mechanism includes a sensitive element in the form of an oval-section tube that compresses like a spring and transmits the force to the measuring module.

Differential

These manometers are considered complex mechanisms and operate on the principle of deformation of internal blocks. These structural elements are sensitive to pressure and, as they deform, transmit readings to the measuring unit. The pointer will move until pressure differences stabilize.

Diaphragm

• Operate on the physical principle of pneumatic compensation.
• The main element of the device is a special diaphragm that bends under pressure.
• The sensitive mechanism tracks these changes and outputs the pressure value.

Accuracy Class of Manometers

This characteristic is always indicated in the device's technical passport. The accuracy class is expressed in numbers: the lower the numerical value in the marking, the higher the accuracy. There are three standard categories:

• With large error. Accuracy class 4.0. These devices are usually used at automotive service stations to check air pressure in tires.
• Standard, in the range of 1.0-2.5 (normal accuracy class for most models);
• High-precision (reference), operating with an error of 0.05.

The accuracy class affects not only measurement error but also the possibility of operating devices within a certain range. Thus, powerful models cannot detect minimal fluctuations, while ultra-sensitive ones are quite susceptible to high "critical" values.

The range of modern models includes devices capable of measuring in the range of 0.06-1000 mPa, as well as modifications for measuring vacuum pressure down to -40 kPa.

The company Izmerkon, Saint Petersburg, sells digital manometers with an LCD display that shows the measured values. Such devices operate with high accuracy, within 0.5-0.025%. Among the company's offerings are models with additional options – for example, in explosion-proof design.