Differential Pressure

How to Choose an Industrial Differential Pressure Instrument

Differential pressure is the pressure difference between two points in a system. Measuring this difference helps monitor filter conditions, detect pressure changes in ducts and supervise industrial process conditions.

Choosing a differential pressure transmitter, switch or gauge requires checking the measuring range, maximum static pressure, process medium, temperature and required indication or output signal.

Types of Differential Pressure Instruments

Differential Pressure Transmitters

Convert the measured pressure difference into a signal for a PLC, automation controller or monitoring system. Depending on the model, analogue current or voltage outputs and optional digital communication interfaces may be available.

Differential Pressure Switches

Provide switching functions for alarms or control actions when specified pressure conditions are reached. The number of contacts, electrical ratings and adjustment options must be checked for each device.

Differential Pressure Gauges

Provide local indication of the pressure difference. Mechanical indicating versions can operate without an electrical power supply. Additional contacts or transmission functions may be available on selected configurations.

Digital Indicators and Transmitters

Combine local display with measurement transmission, parameter adjustment or switching functions, depending on the model. They are useful when operators need to read pressure locally while providing measurement information to a control system.

Key Technical Selection Criteria

Differential Pressure in Air, Gases and Liquids

Air filtration and HVAC applications often require instruments capable of measuring small pressure differences. In hydraulic systems and liquid processes, static pressure, wetted materials and overload resistance may be equally important.

Two instruments with the same differential measuring range are not necessarily interchangeable. Their maximum static pressure and media compatibility may differ significantly.

Fischer Solutions for Different Applications

The Garma catalogue includes Fischer instruments with different measuring principles and configurations:

• DE25: low differential pressure transmitter for air and neutral gases, suitable for ventilation, filtration and HVAC applications.
• DE16: differential pressure transmitter for applications requiring careful evaluation of static pressure and media compatibility.
• DE46: differential pressure measurement and switching instrument, with functions depending on its configuration.
• DA03: differential pressure gauge for local indication in industrial processes, with different construction options.

The exact product configuration must be checked against its technical documentation, especially when alarm contacts, special materials, digital communication or specific approvals are required.

Industrial Applications

• Filtration: monitoring pressure drop across filters to assess their condition.
• Ventilation and HVAC: monitoring pressure differences in ducts and air handling equipment.
• Technical rooms and cleanrooms: monitoring pressure differences between areas using instruments suited to the required range.
• Industrial processes: differential measurement in compatible gas and liquid circuits.
• Maintenance: replacement of existing gauges, switches and transmitters after checking their specifications.