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Flow/Pressure Metrics

The need for pressure or flow monitoring bridges may industries. This article covers some of the basics in the medical, general industrial, and water supply industries.

The fundamentals of pressure and fluid flow don’t really change across the industries. It is necessary to do one of the following:

  • Simply measure pressure because that what’s needed, e.g., to monitor airway pressure in a breathing system.
  • Measure differential pressures across a pneumatic resistance so that flow can be calculated.
  • integrate flow so that the volume/quantity of air/fluid that has been delivered over a given time can be determined.

The means by which these measurements are made are determined by the type of transducers used. The most commonly used are small PCB mounted transducers that conveniently mount on PCBs (printed circuit boards) with tubes connected to them to measure the point/s of interest. These are relatively cheap and can be selected to cope with a multitude of different pressure ranges and types – Honeywell are a supplier of such devices. These are usually more than adequate for most issues. The limitations are they are not good with fluid, particularly when used for differential flow measurement.

Over the last few years ultrasonic methods of determining flow have surfaced. These are particularly interesting when the environments are aggressive because the are essential non-contact methods. The problem, currently, is that the methods of implementation are complex and costly – technology still evolving. 

It is common to analytically analyse a system – fluid flow isn’t straightforward. For example, the pressure differential across a known pneumatic resistance will be different depending on whether the flow through it is laminar or turbulent, and what type flow is present is a complex function of the shape of the device through which there is flow. 

The ET can offer help and guidance with all of this – please feel free to Contact Us, and the ET will be more than happy to discuss your requirements with you.