Rotronic differential pressure transmitter PF4/5 series

Differential pressure is a key variable that needs to be monitored in heating, ventilation, air-conditioning (HVAC), food processing and pharmaceutical sector clean rooms.

Rotronic’s new differential pressure transmitters PF4 and PF5 respectively use thermal mass flow or diaphragm sensor measuring technologies,. Either consistently produces perfect measurement results thanks to an integrated ambient pressure sensor and automatic zero point compensation, either carried out automatically every 5 ms within sensor or performed using an internal valve and operating software.

Both instruments feature a new color display that allows users to display up to four lines and up to three measured values, with all analog outputs, inputs and alarm settings selectable via an intuitive menu.

Thanks to analog and digital communication, both device types can be integrated easily into any monitoring system with options to connect to HygroClip2 sensor or B4 interface for PT100.

PF4 Thermal mass flow vs. PF5 diaphragm sensor measurement

The PF4 and PF5 use two different measurement technologies to measure differential pressure.

• The thermal mass flow technique (with flow sensor) used in the PF4 uses a heating element placed between two temperature-sensitive resistors. Any gas flow moves the temperature profile towards a resistor, which is then measured and evaluated.
• With the diaphragm sensor strain gauge (DSG) technique used in the PF5, air pressure strains a diaphragm, with measuring strips varying their electrical resistance with each pressure pulse. The resultant elongations and compressions are then converted into an electrical signal and evaluated.

Both measurement principles have particular advantages and disadvantages:

Thus it will be seen that the lower vibration sensitivity of the diaphragm sensor makes the PF4 more suitable for HVAC applications while the PF5’s lower risk of cross contamination makes it more applicable to clean room monitoring.

Features and benefits

Based on the PF4 V1, the new PF4/5 series incorporates a range of useful features, notably integrated ambient pressure sensor and automatic zero point calibration. They provide a choice of precise and maintenance-free solutions for differential pressure measurement, whose settings can be changed easily using the intuitive menu on color display.

Both instruments incorporate a sensible range of functions, including:

• Possibility to connect an additional humidity and/or temperature probe
• Analog input for external devices
• Three analog outputs for output of all measured parameters
• Automatic zero-point calibration
• On-board ambient pressure for automatic compensation of measurement error
• New intuitive menu structure
• Network-compatible (Ethernet) interface
• Modbus capable TCP or RTU via RS485 protocol
• Integrated relay switch (potential-free with changeover contacts)
• Use cases integrated into HW4 V3.9.0.operating system software

Resources

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