Catalóg
MEMS pressure sensors are a new type of sensor manufactured by integrating microelectronic technology with micromachining techniques. Thanks to their miniaturised design, they excel in terms of size, accuracy, response speed and power consumption, and are widely employed across a multitude of fields, including automotive electronics, consumer electronics, healthcare, industrial automation and aerospace. This article will delve into the technical principles, performance distinctions and application scenarios of MEMS pressure sensors, providing industry professionals with a comprehensive reference.
Principles and Structure
The fundamental distinctions among MEMS pressure sensors stem from the physical effects they exploit. Different principles define their performance limits and suitable applications. The mainstream technological approaches comprise five major categories—piezoresistive, capacitive, resonant, fibre‑optic, and piezoelectric—each exhibiting markedly divergent characteristics.
1. Piezoresistive Pressure Sensors
Piezoresistive sensors are based on the piezoresistive effect, discovered in 1954: when a semiconductor material (such as monocrystalline silicon) is subjected to mechanical stress, its band structure alters, producing a significant change in resistivity. The core construction features an elastic silicon diaphragm bonded into a Wheatstone bridge: the diaphragm’s periphery is clamped and sealed, while the rear is etched to form an inverted pyramidal cavity. Four piezoresistors are diffused onto the diaphragm surface and wired into a bridge circuit.
When pressure is applied, the diaphragm deforms: one pair of bridge arms increases in resistance while the opposite pair decreases, yielding an output voltage linearly proportional to the applied pressure. To enhance performance, the chip is typically bonded to a glass substrate with a matching coefficient of thermal expansion, affording stress isolation and electrical insulation. Advantages include simple structure, low cost, and suitability for mass production, though temperature compensation is required to mitigate environmental interference.
2. Capacitive Pressure Sensors
Compared with piezoresistive types, capacitive sensors offer superior sensitivity and linear range, along with lower temperature drift and greater stability. However, they require stringent plate insulation, and are susceptible to interference from dust or liquids; their manufacturing cost is relatively higher. In typical applications, a silicon‑to‑glass bonding process creates a vacuum reference cavity, making them well suited for absolute pressure measurements.
Capacitive sensors operate on the parallel‑plate capacitor principle. A silicon diaphragm serves as a movable electrode opposing a fixed electrode to form a capacitor. Applied pressure deforms the diaphragm, altering the plate separation and thus the capacitance. The principal assembly comprises a circular metal‑coated silicon diaphragm (or metallised silicon), a fixed electrode, and a cavity; the capacitance changes are converted to an electrical signal via dedicated measurement circuitry.
3. Resonant Pressure Sensors
The outstanding merits of resonant sensors are high precision and resolution, with a digital output that easily interfaces with modern electronics. However, their fabrication is complex and time‑consuming, and they remain sensitive to temperature and vibration; consequently, they carry a high cost and are typically reserved for high‑end applications such as aerospace and metrology.
Resonant sensors exploit the stress‑frequency effect: the natural resonant frequency of a resonator (such as a silicon beam or diaphragm) shifts in response to stress induced by external pressure. A resonant element and its support structure—commonly realised as a double‑ended tuning fork (DETF) or resonant membrane—are driven and sensed by electronic circuitry, which maintains oscillation and reads out frequency changes.
4. Fibre‑Optic Pressure Sensors
This technology excels in harsh environments—strong electromagnetic fields, high temperatures or corrosive media—and offers compactness and remote sensing capability. Yet the high cost of optical components, the intricacy of system calibration, and the stringent demands of fibre‑to‑diaphragm bonding have constrained its widespread adoption.
Fibre‑optic sensors utilise the Fabry–Pérot interferometer principle: one end of the optical fibre is coated with a semi‑reflective mirror, while the other end terminates at a movable diaphragm mirror. Pressure variations shift the diaphragm’s position, changing the optical path difference between the two reflective surfaces; analysing the resulting interference fringe shifts allows pressure to be determined. The main components are the optical fibre, diaphragm mirror and sealed cavity, conferring innate immunity to electromagnetic interference.
5. Piezoelectric Pressure Sensors
Piezoelectric sensors harness the piezoelectric effect: certain materials (e.g. aluminium nitride (AlN) or lead zirconate titanate (PZT)) generate an electric charge in response to mechanical stress. The core structure comprises a piezoelectric thin film or ceramic element. Requiring no external power, they function as self‑powered transducers.
Piezoelectric sensors deliver extremely rapid dynamic response (on the order of milliseconds), making them ideal for transient pressure monitoring (such as explosions or shock events). However, they cannot measure static pressure, their outputs are inherently low‑level and necessitate complex amplification circuits, and their long‑term stability is relatively poor.
| Type | Core Principle | Internal Structure |
|---|---|---|
| Piezoresistive | Semiconductor piezoresistive effect: resistance changes with applied stress | Elastic silicon diaphragm + diffused piezoresistors (Wheatstone bridge) |
| Capacitive | Parallel‑plate capacitance: capacitance varies with electrode spacing | Movable diaphragm electrode + fixed electrode + cavity |
| Resonant | Resonator frequency shifts with applied stress | Silicon beam/diaphragm resonator + drive & sense circuitry |
| Fibre‑optic | Optical path‑length change causes interference fringe shift | Optical fibre + semi‑reflective mirror + movable diaphragm mirror |
| Piezoelectric | Piezoelectric effect: mechanical stress generates charge | Piezoelectric film/ceramic element + electrodes |
Performance Comparison
Íogaireacht: Resonant and fibre‑optic excel
Piezoresistive: Íogaireacht ard, sufficient for most industrial applications.
Capacitive: Superior sensitivity to piezoresistive, with a wide linear range.
Resonant: Extremely high sensitivity, ideal for precision measurement.
Fibre‑optic: High sensitivity and low susceptibility to environmental interference.
Piezoelectric: Outstanding dynamic sensitivity, but poor static performance.
Power Consumption: Capacitive and piezoelectric are best
Piezoresistive: Moderate consumption (mA‑level); requires continuous power to maintain the bridge.
Capacitive: Low consumption (μA‑level); detection circuitry draws minimal current.
Resonant: Relatively high consumption (mA‑level); excitation circuit must sustain oscillation.
Fibre‑optic: Extremely low consumption; well suited to remote, passive monitoring.
Piezoelectric: Zero power consumption (self‑powered); only the signal‑conditioning circuit requires energy.
Environmental Adaptability: Fibre‑optic and piezoelectric withstand extremes
Operating Temperature Range:
Piezoelectric > Fibre‑optic > Resonant > Piezoresistive/CapacitiveImmunity to Interference:
Fibre‑optic > Piezoelectric > Resonant > Capacitive > Piezoresistive
Cost and Integration: Piezoresistive leads
Cost: Piezoresistive < Capacitive < Piezoelectric < Resonant < Fibre‑optic
Chip Footprint: Piezoresistive/Capacitive < Resonant < Fibre‑optic
| Feature | Piezoresistive | Capacitive | Resonant | Fibre‑optic | Piezoelectric |
|---|---|---|---|---|---|
| Íogaireacht | High | Excellent | Ultra‑high | High | High (dynamic) |
| Cobhsaíocht | Requires temperature‑drift calibration | Low drift | Good stability | Immune to electromagnetic interference | Long‑term stability uncertain |
| Power Consumption | Moderate (mA‑level) | Low (µA‑level) | High (mA‑level) | Extremely low | Zero (self‑powered; only signal‑conditioning draws power) |
| Environmental Suitability | Unstable under high shock/vibration | Performance degrades in dusty or liquid environments | Sensitive to temperature and vibration | Suitable for harsh environments | Wide choice of materials |
| Cruinneas | Moderate | Excellent | Ultra‑high | High | Moderate |
| Cost | Low | Moderate | High | Very high | Moderate |
Application Scenarios
1. Automotive Industry
The automotive sector represents the largest single market for MEMS pressure sensors, accounting for over 35 % of total demand. Piezoresistive sensors are extensively used in engine management, braking systems and tyre‑pressure monitoring, for instance to measure intake‑manifold pressure or brake‑line pressure. Capacitive sensors find roles in comfort systems (e.g. seat‑pressure monitoring), while resonant sensors serve high‑precision pressure measurement applications. Premium vehicles may incorporate hundreds of sensors, of which around ten are MEMS pressure devices, supplying critical data for optimising engine performance, improving fuel efficiency and enhancing safety.
2. Leictreonaic Tomhaltóra
With the rise of 3D navigation, motion tracking and health monitoring, MEMS pressure sensors are increasingly embedded in consumer gadgets. Piezoresistive and capacitive types power the barometers, altimeters and indoor‑positioning features in smartphones, tablets and smartwatches. In drones and model‑aircraft, MEMS pressure sensors deliver altitude data that aids flight‑control systems in maintaining precise navigation.
3. Healthcare
In the medical field, MEMS pressure sensors are integral to a variety of devices and diagnostic systems. Capacitive sensors—valued for their stability—are employed in blood‑pressure monitors, ventilators and anaesthesia machines. Piezoresistive sensors, offering high sensitivity, are used in implantable pressure monitors and drug‑delivery pumps.
4. Industrial Automation
MEMS pressure sensors monitor and regulate countless industrial processes. Piezoresistive sensors excel in liquid and gas pipeline monitoring and liquid‑level detection. Fibre‑optic sensors, with their superior immunity to electromagnetic interference, perform reliably under harsh industrial conditions. Resonant sensors are chosen for applications demanding ultra‑high accuracy in process control.
5. Aerospace
In aerospace, MEMS pressure sensors support aerodynamic testing, high‑altitude pressure monitoring, meteorological data acquisition and pressure regulation in airborne and space‑borne equipment. Resonant and fibre‑optic sensors are favoured for their exceptional precision and resistance to interference, meeting the rigorous demands of flight and space environments.
Selection Guide
1. Clarify the Measurement Type
Absolute‑pressure sensor: Measures absolute pressure; the sensor contains its own vacuum reference, so readings are independent of atmospheric pressure. Ideal for barometric and altitude measurements.
Gauge‑pressure sensor: Measures pressure relative to ambient atmosphere; uses atmospheric pressure as the reference. Suitable for applications such as vessel or pipeline pressure monitoring, where fluctuations in atmospheric pressure must be negated.
Differential‑pressure sensor: Measures the difference between two pressures via dual inlets. Commonly used in flow‑rate measurement and filter‑monitoring applications.
2. Determine the Pressure Range
Over‑pressure capability: Distinguish between static and dynamic (impact) pressure. For pulsating or shock environments, select a sensor with higher over‑pressure tolerance.
Accuracy vs. range: Sensor accuracy often varies across its span. Choosing a range close to your operating pressure makes it easier to meet precision requirements.
Cost vs. range: Sensors in the 0.3–1 MPa band typically offer the best value; ranges below 0.1 MPa or above 1 MPa tend to be more expensive.
3. Assess Accuracy Requirements
Accuracy is influenced by non‑linearity, hysteresis, repeatability, temperature effects, zero‑offset stability, calibration and humidity. Static accuracy over the full temperature range is categorised as:
Ultra‑high (0.01–0.1 % FS)
High (0.1–1 % FS)
Standard (1–2 % FS)
Low (2–10 % FS)
Specify the precision tier suited to your application—bear in mind that higher accuracy incurs greater cost.
4. Check Electrical Specifications
Output Signal:
Digital: I²C or SPI outputs for direct interfacing with microcontrollers.
Analogue: 0–5 V or 0–10 V voltage outputs; 4–20 mA current loops for industrial control systems.
Choose the output type compatible with your measurement or control hardware.
Excitation Source:
Constant‑current excitation is preferred for minimising thermal‑sensitivity drift in precision measurements.
Constant‑voltage excitation is simpler but may require external temperature‑compensation resistors or diodes.
Some sensors support proportional or fixed excitation modes; select according to stability and power‑consumption needs.
5. Consider the Operating Medium and Environment
Medium compressibility:
Gases are compressible—pressure surges can impart shock loads on the diaphragm.
Liquids are incompressible—ensure installation avoids pressures exceeding the sensor’s maximum rating.
Harsh environments: In the presence of strong vibration, shock or electromagnetic interference, specify enhanced over‑pressure protection, robust mechanical sealing, and EMI‑shielded, grounded cabling.
Chemical compatibility: Diaphragm materials must resist corrosive or flammable media. For explosive atmospheres, use minimal excitation current and add protective housings rated for the application.
6. Define the Operating‑temperature Range
Typical sensor grades are:
Commercial (–10 °C to +60 °C)
Industrial (–25 °C to +80 °C)
Automotive (–40 °C to +125 °C)
Military (–55 °C to +125 °C)
Specialised (–60 °C to +350 °C)
Choose the grade matching your ambient conditions. For outdoor or extreme environments, consider industrial or automotive grades, or thermally isolate the sensor to reduce calibration complexity.
7. Verify Sealing Requirements
Common sealing methods include O‑rings, epoxy resins, PTFE gaskets, taper‑fit ports, threaded fittings and welding. The choice of sealant determines the sensor’s usable temperature and chemical compatibility—select sealing materials suited to your temperature range and process media.
Conclusion
MEMS pressure sensors are available in a wide array of types, each featuring its own distinctive operating principle, performance attributes and suitable applications. When selecting a sensor, one must take into account the intended use, pressure range, accuracy, electrical specifications, operating medium, temperature range and sealing requirements to ensure the most appropriate device is chosen for the specific application. As technology continues to advance, the deployment of MEMS pressure sensors across diverse sectors will become increasingly widespread, offering enhanced support for industrial practice and technological development.
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