Protecting MEMS Pressure Sensors with Parylene

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities, and you.

Protecting MEMS Pressure Sensors with Parylene

Microelectromechanical systems (MEMS) pressure sensors provide accurate measurements for many applications. However, the top side of the piezoresistive MEMS pressure sensor die that has the sensing elements and potentially other circuitry cannot survive exposure to many common items that need to have their pressure measured — including water. To isolate the top surface of the pressure sensor die and other exposed circuitry, parylene is often used as a protective coating. Applied by a vapor deposition polymerization process, the parylene allows pressure to be transmitted to the top side of the pressure sensor to make measurements without damaging or impacting the reliability of the circuitry. The conformal, thin-film coating provides a moisture, chemical and dielectric barrier to protect the sensor’s critical circuitry in medical, automotive and other applications.

In fact, parylene extends the applications that a specific sensor design can address and is part of the packaging expertise that a sensor company may provide. Parylene coating can be found on a wide variety of All Sensors’ products. Specifically, parylene coating is available in all miniature digital product families such as the miniature digital DLVR, DLHR and DLLR Series as well as the millivolt output MLV series and the miniature digital and analog ELVR series.

All Sensors' E1BD Package

 

A protective parylene coating is an option for moisture/harsh media protection in the DLVR, DLHR and DLLR Series E1BD package.

Comments/Questions?
Do you have a pressure sensing question? Let us know and we’ll address it in an upcoming blog.
Email us at info@allsensors.com

Critical Flight Measurements Using Pressure

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities and you. In this blog we’ll be discussing critical flight measurements using pressure.

Critical Flight Measurements Using Pressure

Amplifying the low level signal from a higher pressure range sensor for a low pressure application can frequently lead to unacceptable noise problems in the application. This can occur if the sensor supplier performs this task as part of an amplified and signal-conditioned product offering or if the customer performs the amplification and signal conditioning. The limitation is inherently in the sensor die. Specially designed lower pressure range sensors, such as All Sensors DLVR Series mini digital output pressure sensors offer a solution to the noise problem.  The low mass, high-sensitivity die are less sensitive to errors due to vibration or changes in time, temperature and position.

All Sensors’ CoBeam2 TM die technology achieves a high level of pressure sensitivity without using boss structures and larger die topologies commonly used in microelectromechanical system (MEMS) designs. This design approach significantly reduces gravity and vibration sensitivities. As shown in Figure 1, CoBeam2 technology combines bonded strain gage sensor insight with state of the art MEMS processing.

31A

Figure 1 MEMS pressure sensor die using CoBeam2 technology

Figure 2 shows active dual-die compensation with electrical cross coupling of the sensors’ outputs and pneumatic cross coupling of the pressure used in the DLVR Series and other All Sensor products. By performing both electrical and pneumatic cross coupling, the signal strength is not reduced and the common mode error compensation is optimized. Some products use just the electrical cross coupling. Pressure Point 4: Dual Die Compensation for MEMS Pressure Sensors provides more details. Combined with CoBeam2 Technology, the amplified, digital output sensor reduces many errors associated with pressure measurements.

31B

(a)                                                                                      (b)

Figure 2  (a) Electrical cross coupling compensation of active die (Die 1) using a reference die (Die 2) and (b) pneumatic cross coupling compensation using fluidic channels in the pressure sensor package.

Drones, multicopters, quadcopters, small unmanned air vehicles (UAVs) and micro air vehicles (MAVs)  are not only the rage in modern flying craft, they are among the applications that can benefit from the improved sensor performance of a small form factor MEMS sensor.  Low pressure sensors such as the 1 inH2O DLVR-L01D up to the 10 inH2O DLVR-L10D can be used for measuring differential pressure on the wing in multiple locations to provide improved control and stability. Higher pressure ranges are also available.

Wind tunnel testing has traditionally used several pressure sensors on the wings of a test aircraft to provide a pressure-based estimation of the flow field above an airfoil. Recently, for increased control in drones, aerodynamics-based feedback using onboard active flow control schemes relies on a set of pressure measurements taken across the aircraft through pressure ports and through multi-hole probes. The aerodynamic feedback can be especially useful when switching control modes during various flight conditions.

Highly turbulent situations can also pose attitude control difficulties for fixed-wing MAVs. In Bioinspired Wing-Surface Pressure Sensing for Attitude Control of Micro Air Vehicles, researchers are investigating alternate technique using pressure sensors to solve this problem.

Other flight measurements can benefit from highly stable pressure sensors. For example, the DLV-015A DLV Series mini digital output absolute sensor can provide the barometer or altimeter readings in these same aircraft.

CoBeam2 is a trademark of All Sensors Corporation.

What do you think/Comments?
Do you have a pressure sensing question? Let me know and I’ll address it in an upcoming blog.
-Han Mai, Senior Marketing Specialist, All Sensors Corporation (hmai@allsensors.com)

New DLV Series Low Voltage Digital Pressure Sensor

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities and you. In this blog we’ll look at All Sensors’ new DLV pressure sensor.

New DLV Series Low Voltage Digital Pressure Sensor

All Sensors has announced a new DLV Series Low Voltage Digital Pressure Sensor. The DLV Series is based on the already popular DLVR Series Pressure Sensors. This new device series offers design engineers excellent performance over middle pressure ranges of 5 to 60 psi compared to the DLVR low pressure ranges of 0.5 to 60 inH2O.

Product highlights include supply voltage options to ease application integration into a wide range of process control and measurement systems and multiple power consumption modes for battery-powered or remote systems. The DLV Series provides a calibrated and compensated output over a wide temperature range of -20°C to 85°C.

The DLV Series embodies innovative features:

  • 3.3V or 5V supply voltage
  • I2C or SPI interface
  • Better than 0.5% accuracy over temperature (typical)
  • Sil-Gel die coating is added for enhanced media protection
  • Miniature packaging with SIP and DIP lead configurations

Ideal applications for this device include:

  • Medical breathing
  • Environmental Controls
  • HVAC
  • Industrial controls
  • Portable devices/hand-held equipment
  • Other applications measuring clean, dry air and gases

Datasheet download here. Samples are available for product testing.

E1BD

What do you think/Comments?
Do you have a pressure sensing question? Let me know and I’ll address it in an upcoming blog.
-Dan DeFalco, Marketing Manager, All Sensors Corporation (ddefalco@allsensors.com)