The Right Features for Accurate Pressure Sensing in Harsh Environments

More and more designers are integrating pressure sensors to replace less accurate pressure switches in applications such as thermal cycling processes to improve efficiency and to enable additional system automation. The latest generation of pressure sensors leverages the benefits from MEMS technology, which provides extremely accurate condition readings in a miniature package size. These advancements have led to greater usage of pressure sensors in a broad variety of industrial applications that include energy, heavy equipment, transportation, food & beverage or in certain medical environments.

A key consideration for selecting the optimum pressure sensor for a given application is whether it must frequently operate in severe conditions. That’s because dust, chemicals, shock and vibration and high temperature all threaten a sensor’s performance, reliability and longevity. Designers have found that the large majority of PCB-mount sensors available many times feature limited harsh media capabilities. Their resistance is often restricted to dry gases or non-aggressive liquids, with narrowly-calibrated temperature and pressure ranges.

But what should a designer look for in a sensor to ensure it can handle extreme conditions?

There are a few important attributes to be judged when evaluating pressure sensors. The pressure range of the sensor and its media compatibility compared to the application’s pressure measurement and feedback should be the first considerations. Pressure sensor accuracy is another important performance feature to review. Package size and power consumption are also critical in many space-constrained applications.

Working with potential customers, Bourns recognized that they would be best supported with a pressure sensor design that delivers a combination of harsh media compatibility, wide temperature operation and with the ability to handle a high pressure range. Many designs also required all these features in a single small form factor device.

When looking for a sensor for harsh environments, its construction is a key evaluation point. Sensor designs based on an adhesive-free die attach mounting process using a eutectic die bond on ceramic results in a robust device structure capable of handling high pressure ranges even at high temperatures.

Another advantage of an adhesive-free design is that it can be combined with backside pressure measurement. Backside sensing is a type of pressure sensor design whereby the measured media only touches the backside of the measurement element. Using backside measurement permits construction with a small number of media-resistive wetted materials. A distinct sensor accuracy benefit is that all electronic components and other sensitive surfaces are automatically isolated from the media. Wetted materials are all materials in contact with the measured media, therefore, the wetted materials are most critical in terms of media resistivity of the sensor.

sc1949_bps140Bourns® Model BPS140 pressure sensors use a robust device structure capable of handling high pressure ranges (15 to 500 PSI) even at high temperatures. The new model series further expands Bourns® environmental sensor line delivering high sensitivity and accuracy in extended temperature applications. It also features a ceramic port to enhance compatibility with certain harsh media.

A further advantage of the new sensor construction techniques used by Bourns make it possible to integrate the measurement functionality of stainless steel and media-isolated pressure sensors at the PCB level. This leap forward in design brings measurement functions and additional value into designs. By enabling more functions to be integrated at the PCB level, today’s pressure sensors contribute to reduced wiring complexity, lessen the risk of signal distortion because of environmental noise and also help to decrease the number of sealed electrical connections. sc1949_splash_bps130_whitepaperWhen evaluating a pressure sensor for your next design, a Bourns white paper provides the important sensor construction features to consider when selecting the right pressure sensor for accurate readings in certain harsh media applications.

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