Traditional Pressure Sensor Issues
Because of their contact with aggressive media, fuel and other harsh environmental conditions, fuel pressure sensors often deteriorate over time and need replacement – they are often the cause of an automobile failing emission inspections. However, new robust fuel pressure sensor technology improves the overall lifetime of sensors, reducing maintenance, total ownership costs, and help carmakers better conform to new emission legislation.
Pressure sensors that have a long service life, and are able to operate accurately throughout their lifespan, are a crucial requirement. In addition, they must be highly reliable when used in mandatory on-board diagnostics and control systems.
Traditional fuel pressure sensors use soft elastomer materials (a rubber-like solid with elastic properties that are held together by weak intermolecular bonds) for the interconnection of the sensor’s packaging and its sensing element. When this comes into contact with the fuel media the “soft glues” in elastomers break down over time and is a known weakness for accurate measurements and long-term stability. This issue is compounded with an ever-increasing variety of fuels, mixtures, additives and conditioners used in different countries across the globe.
Reliable Pressure-Sensing Technology
New advanced pressure sensing technology not only improves the overall service life of fuel pressure sensors, but enables a more reliable and accurate measurement. These sensors take a different approach altogether by replacing all plastics and elastomers that come into direct contact with fuel media with an extremely durable CTE-matched glass-based material. These sensors are matched in terms of thermal expansion.
Due to the glass-based design, these materials do not become brittle, swell or shrink, unlike elastomer-based sensors. This eliminates inaccurate pressure measurements and leakage that leads to signal drift. It also enables a flexible integration in applications with temperatures up to +125°C.
As a result, this advanced pressure-sensing technology offers a high resistance against all fuel media and other harsh environmental conditions. It provides an accurate signal with a narrow tolerance of less than ±1 percent FS (full scale accuracy) over a wide-temperature range of -40 °C to +125 °C. This is true even when temperature changes in short time periods.
Different manufacturers offer a wide variety of application-specific housing and connector options.
In selecting this new technology, engineers should determine what of these options best suit their applications. They can often reduce costs and build of materials by choosing a sensor platform that can be applied to multiple fuel applications with only slight changes to the configuration of the housing and connectors of these sensors.
One of the issues surrounding hybrid vehicles is leakage controls. New, innovative tank pressure sensors based on the same CTE-matched glass-based material addresses leakage controls and pushes the limits of accuracy for sensors.
Evaporation emissions control systems are designed to prevent fuel vapor from being discharged into the atmosphere. Pressure sensors must monitor the tank pressure either during electrical driving mode or when the vehicle is resting. They must detect minute pressure and temperature deviations that affect efficiency.
For example, with an improved calibration that was developed specifically for the leakage control algorithm, a new tank pressure sensor from TDK offers a high relative accuracy of just 0.2 percent, as well as a long-term signal stability and high media resistance over its lifetime.
Similarly, new tank pressure sensor technology for hybrid vehicles offers gauge pressure measurement over a wide range, typically from -100 mbar to 350 mbar. When selecting such sensors, engineers should the manufacturer offers a digital interface for on-board diagnostics and additional temperature sensing.
As automakers employ new fuel pressure sensors to reduce fuel consumption and vapor emissions, they should feel confident that the technologies they use will be reliable and accurate for a long period of time. They shouldn’t have to worry about contact with media, nor the overall service life of fuel pressure sensors. New fuel pressure sensor technologies address this and help to ensure that the overall efficiency of combustion engines increases.
About the author
Paul Mason is director of temperature, pressure and bio-mems sensors at TDK Electronics Inc. He has 27 years of electronic components industry experience, including a decade in SAW multimedia sensors product management. He holds a Bachelor of Engineering with honors degree in Electronic and Electrical Engineering from Salford University, U.K.