Flow Measurement with Differential Pressure Sensors
Accurately monitoring the flow of gases and liquids is a key requirement in industries ranging from HVAC and building automation to medical technology and industrial processing. One of the most robust and widely used methods for this task is flow measurement using differential pressure sensors. These sensors offer precise, reliable, and maintenance-friendly performance, particularly in applications where flow rates must be monitored with minimal pressure loss and maximum long-term stability.
How Flow Measurement via Differential Pressure Sensors Works
Flow measurement using a differential pressure sensor applies Bernoulli’s principle by creating a measurable pressure change (Δp) within a flow system through a defined restriction such as an orifice plate, a Venturi tube, or a laminar flow element. This pressure difference, measured by a differential pressure sensor in a bypass channel, is proportional to the volumetric flow rate (Q resp. V̇ ). The mass flow rate (ṁ) can be calculated from this if the density of the measured media is known. This requires additional temperature and barometric pressure measurement.
As laminar flow elements produce a velocity-pressure drop relationship that can be considered linear, it is for many applications the preferred measurement method. For cylindrical pipes the Hagen–Poiseuille equation describes the relationship between the pressure difference and the resulting volumetric flow rate of a homogeneous Newtonian fluid with dynamic viscosity η, flowing laminarly through a pipe of radius r and length l. Depending on the applications design it can be necessary to measure differential pressures as low as 1 mbar and lower.
By integrating the flow rate over time, the total volume such as the air volume in respiratory systems can also be determined.
Ideal for Low Pressure Ranges and Sensitive Flow Applications
Differential pressure sensors with very low measurement ranges – down to just a few millibars – are especially well-suited for applications in which the pressure drop must be minimal. This is crucial for ensuring:
- Minimal breathing effort for patients in medical ventilation
- Low energy loss in HVAC and climate control systems
- Minimal system interference in laboratory or industrial monitoring
For these use cases, sensors must exhibit exceptional measurement sensitivity, long-term stability, and baseline accuracy. In medical respiratory devices, for example, the bidirectional flow during inspiration and expiration must be captured with high zero-point stability to detect even the smallest breathing signals.
Application Examples
Why All Sensors?
Flow measurement using differential pressure sensors is employed across various industries:
- Medical Technology: Breathing parameters in ventilators and spirometers
- HVAC Systems: Monitoring airflow in ducts for energy efficiency and system control
- Filter Monitoring: Detecting increased flow resistance in clogged filters
- Process Engineering: Flow monitoring of liquids and gases in pipelines
- Environmental and Laboratory Equipment: Monitoring laminar airflow or exhaust systems
All Sensors specialises in highly sensitive, ultra-low pressure differential pressure sensors with advanced MEMS technology. Our membrane based patented CoBeam²™ and dual-die designs offer superior stability, repeatability, and no risk of clogging. We also provide customised sensor solutions tailored to your exact flow conditions – whether for mobile medical devices, compact HVAC units or complex industrial systems.
Your benefits with differential pressure sensors from All Sensors:
- Maximum sensitivity even at the lowest pressures
- Available with digital interfaces for easy integration
- Low power consumption for mobile and battery-powered systems
- Custom adaptations and compact designs on request
- Membrane based: no flow through with risk of clogging
Let’s Talk About Your Flow Measurement Project
Choosing the right differential pressure sensor is key to achieving accurate, long-term flow monitoring. Our experts will assist you with selecting the right technology, integrating the sensor into your system, and even customising the sensor for your specific application.
Contact us today to learn how our differential pressure sensors can improve your measurement reliability and system performance.
