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Measuring airflow is important for many HVAC, industrial and medical applications. Whether it is ensuring an air conditioning system is running smoothly or a hospital ventilator is providing the right amount of air to the patient, airflow measurements provide critical system feedback.

The number of systems that require feedback on airflow measurement is extensive.

Image Credit: Superior Sensor Technology

Here are a few examples of the feedback provided:

Figure 1. Some Typical Airflow Applications. Image Credit: Superior Sensor Technology 

The most common device for measuring airflow is a mass airflow sensor. However, in certain scenarios, a differential pressure sensor is a better solution. Let’s take a look at the two devices and their unique advantages. 

A mass airflow sensor is a device with two pressure ports where air/gas flows from the first port to the second. Inside, there’s a sensing element with a heated surface.

As air or gas flows across the sensing element, heat is transferred. This creates a thermal imbalance proportional to the flowing mass. Note that the sensor is measuring the mass flow under standard conditions, not the actual volume of gas flowing through it.

While most sensors are compensated for the effects of temperature, changes in atmospheric pressure that affect the density of the gas may affect the output.

Thus, mass airflow sensors may also require an additional barometric sensor to compensate for variations in atmospheric pressure.

Finally, mass airflow sensors must be calibrated for a specific gas mix, as different gases have varying thermal characteristics. Consequently, mass airflow sensors are susceptible to errors when operating in an environment with changing gas mixtures. 

Benefits mass of airflow sensors:

Challenges with mass airflow sensors:

Figure 2. Image of typical mass airflow sensor. Image Credit: Superior Sensor Technology 

Like a mass airflow sensor, a differential pressure sensor also has two pressure ports. But unlike the flow sensor, there is no gas flow between the two ports of a differential pressure sensor.

Instead, there is a diaphragm between the ports that measures the pressure difference between them. The two pressures to be measured are applied to opposite sides of the diaphragm.

The deflection of this diaphragm, either positive or negative to the zero state, determines the difference in pressure. 

Differential pressure sensors have many uses and can be used to replace mass airflow sensors by measuring the differential air pressure across an orifice. As with any solution, there are positives and a negative in doing so: 

Benefits of differential pressure sensors over mass airflow sensors:

Challenges of differential pressure sensors compared to mass airflow sensors:

Figure 3. Superior’s Differential Pressure Sensor. Image Credit: Superior Sensor Technology

Having an extremely low noise floor, Superior’s differential pressure sensors are ideal for precise air flow measurements.

However, the advantages extend beyond the low noise floor. Some of Superior’s application-specific building blocks provide additional benefits compared to mass airflow sensors. 

Multi-Range technology allows one pressure sensor to operate at maximum performance over several different pressure ranges.

Unlike mass airflow sensors and other differential pressure sensors, Superior’s Multi-Range allows pressure ranges to be changed ‘on the fly’ so that one device in the field can be used to serve multiple purposes.

One of the biggest impediments of differential pressure sensors is the errors caused by the noise generated from fans, blowers and other elements.

Utilizing an integrated advanced digital filtering technology, Superior’s pressure sensors eliminate the noise created by these factors prior to their reaching the sensor sub-system. Thus, the noise is eliminated before it becomes an error signal that can lead to inaccurate airflow reading. 

Superior’s unique dual-die implementation in our 210 models of sensors maintains consistent and highly accurate handheld readings regardless of the physical orientation of the end device.

For time-critical applications, the interval in which it takes the pressure sensor to update its measurement data is vital. The faster you receive updated pressure measurements, the more accurate your output. While user-configurable, Superior’s sensors support update rates as fast as 1 millisecond. 

Long-term stability is defined by the maximum change in zero signal and output span signal of a pressure sensor under reference conditions within one year. This value is of greater importance in low-pressure ranges as the effect on the signal is stronger.

Factors such as temperature and mechanical stress can have negative effects on long-term stability. Superior has market-leading long-term stability measured typically within 0.15% of FSS within the first year. 

For handheld and other battery-operated devices, power consumption is another important factor in overall performance. With power consumption as low as 5 mA, Superior’s products will not adversely impact the battery life of even the most sophisticated equipment. 

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This information has been sourced, reviewed and adapted from materials provided by Superior Sensor Technology.

For more information on this source, please visit Superior Sensor Technology.

Please use one of the following formats to cite this article in your essay, paper or report:

Superior Sensor Technology. (2022, February 07). The Benefits of Pressure Sensors for Measuring Airflow. AZoSensors. Retrieved on October 22, 2022 from https://www.azosensors.com/article.aspx?ArticleID=2438.

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