Pressure Sensors

Pressure Sensor Construction Addresses Challenges in Wet Environments

January 8, 2016 By: Karmjit Sidhu, TE Connectivity

Sensors Insights by Karmjit Sidhu

Low Pressure

Accurate measurement of low pressure with respect to atmospheric reference (typically called vented or gauge reference) requires that pressure sensors breathe under dry, humid and wet conditions. In humid and wet environments, challenges are posed on how to operate the pressure sensor without allowing water into the back end of the sensors, causing the device to malfunction. In submersible water applications, the atmospheric-to-depth temperature differential can be significant for a pumping effect to occur where moist air can be drawn into the sensor via the vent line, causing condensation to attack sensitive electronic components to fail.

Low pressure can be termed as 500PSI (35Bar) or below where accurate measurements are to be made without the influence of altitude or barometric changes. As the full span of the pressure that is being measured increases, the effect of barometric pressure becomes a smaller percentage. Measuring pressure with a 5 PSI pressure transducer and 500 PSI pressure transducer will both have the same effect on their respective diaphragms, but the barometric pressure will change the output signal more on the 5 PSI than the 500 PSI transducer.

Sometimes, in outdoor applications where the pressure sensor is mounted to a water pump or another location that is exposed to the environment, a sealed gage or absolute referenced sensor may be used if the overall accuracy is not of significant importance. For example, a sealed gauge pressure sensor used on a water pump running at 150PSI can experience a 4 to 5 PSI difference based on atmospheric and ambient temperature changes. The 2.5-3.5% error may not be an important to the overall system; however, it does protect the sensor against the wet environment. Since the sensor is sealed, it is protected against water ingress through venting.

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About the Author: Karmjit Sidhu

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