Thus, very low power sensing systems, can be designed and implemented that require only a small bias to the circuit by an external reader, making them ideal for remote or implanted medical applications. Moreover, capacitive pressure sensors have low power consumption since there is no DC current flowing through the sensor element due to its nature. Even though they may require more complex signal conditioning circuits and calibration algorithms, they have higher accuracy and lower total error band. In comparison to piezoresistive sensors, capacitive pressure sensors offer many advantages. Technology Comparison, Piezoresistive vs. This variation in capacitance is then translated to an electrical signal where it can be read and conditioned by an ASIC or microcontroller. When pressure is applied, the top plate (or membrane) bends and a capacitance Δ is created. The bottom plate is fixed while the top one is sensitive to pressure changes. Two parallel and electrically isolated conducting plates are needed to ensure that a capacitive pressure sensor operates efficiently. Due to their widespread and low production cost, piezoresistive pressure sensors are widely used in consumer electronics and the automotive industry, as well as in household appliances.Ĭapacitive Technology Measurement Principle The piezoresistive pressure measurement principle is one of the firstly developed in MEMS technology and it was developed many years before the capacitive one. Any perceptible change in resistance is being converted, through a Wheatstone bridge circuit into an output voltage. In piezoresistive sensors, four resistors are placed on a silicon diaphragm in order to measure the result of strain or physical pressure applied upon them. The term piezoresistive is composed by the Greek word “piezo” (meaning squeeze or press) and resist. In this article, we will be discussing their main differences and we will be highlighting the advantages of each. The majority of the pressure sensors currently installed in the field are based on MEMS technology and utilize either piezoresistive or capacitive measurement principle.
1.This is a guest blog post reproduced with permission from ES Systems, a specialist in high quality pressure sensors for a variety of applications. A commonly-available quartz piezoelectric sensor (without enclosure) is shown in Fig. Natural single-crystal materials (quartz, gallium-phosphate, tourmaline, etc) are less sensitive but have higher stability. The sensitivity of ceramic materials is higher than that of natural single-crystal materials, but their high sensitivity degrades over time. Two main sensing materials used for piezoelectric sensors are piezoelectric ceramics (such as PZT ceramic) and single-crystal materials (such as quartz).
Generated piezoelectricity is proportional to the pressure applied to solid piezoelectric crystal materials. The ability of piezoelectric material to convert mechanical stress into electrical charge is called a piezoelectric effect.
The prefix piezo is Greek for press or squeeze. A piezoelectric sensor, also known as a piezoelectric transducer, is a device that uses the piezoelectric effect to measure changes in pressure, acceleration, temperature, strain or force by converting these into an electrical charge.
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