Where Precision Matters: Applications for the PSA071040 Pressure Sensor

The PSA071040 from PUI Audio is a MEMS pressure transducer designed to deliver accurate and repeatable pressure measurements over a range of –40 kPa to +40 kPa. In our previous article, we examined the sensor’s internal structure and electrical performance. This article focuses exclusively on the documented applications and design guidelines as provided in the technical materials.

Documented Applications

The PSA071040 is listed as suitable for the following applications:

• Medical: Pressure Monitoring Devices
  The sensor’s ability to detect small pressure variations makes it a suitable candidate for medical devices such as Blood Pressure monitors, inflatable cuffs (e.g., for anesthesia or airway management).
• Medical: Oxygen Generator
  The linear response of the sensor supports its use in oxygen generation systems where precise pressure control and monitoring are necessary.
• Security: Special Room monitoring (e.g., Data Centers, Labs)
  The sensor ensures the environment is sealed and under expected pressure; deviations could indicate a breach.
• Consumer: Tire Pressure Gauge
  The sensor’s pressure range is appropriate for use in automotive tire pressure measurement, whether used in a handheld gauge or integrated into a Tire Pressure Monitoring System (TPMS).
• Consumer: Massage Chair
  The sensor can be integrated into pressure monitoring systems for massage chairs, where it tracks the pressure in air bladders or similar mechanisms to adjust the message intensity.
• Consumer: Coffee Machines
  The sensor is also applicable in coffee machines, where monitoring brewing pressure is an important aspect of system control. The sensor enables features like pre-infusion pressure monitoring, allowing machines to optimize extraction profiles for improved flavor and consistency.
• Industrial: Water Pumps
  The PSA071040 can provide pressure feedback in water pump systems, helping monitor and control operation, trigger on/off cycles, and alert users to low-pressure conditions.

Note: The documents provide these applications as suggested use cases without additional descriptors or certifications. All claims remain strictly within the scope of the provided materials.

Application Circuit

The circuit shown in Figure 1 is a PSA071040 bridge pressure sensor circuit whose output voltage is conditioned and amplified. To facilitate remote sensing, a current mode bridge drive is used. A four-wire shielded cable is used to connect to the remotely located bridge to the conditioning circuit. The OP177 precision operational amplifier serves the bridge current to 1.67mA, driven by a 1.235V AD589 reference voltage. A PNP transistor buffers the drive current supplied by the OP177 operational amplifier. This further ensures the lowest operational amplifier self-heating, and highest gain linearity.

The PSA071040 produces a typical output of 75mV when exposed to a 40kPa pressure. The signal is amplified by the AD620 in-amp, which is configured for a gain of 75 using an effective RG of 619Ω and the potentiometer set to 46Ω. Full-scale voltage calibration is set by adjusting the 100Ω gain potentiometer such that, for a pressure of -40kPa, the output reads -10.125V; and for 40kPa pressure, the output registers 10.125 V. For applications that require digitization, use an ADC that has a 10 V full-scale input range.

Other design considerations include the 0.1F capacitor connected across the AD620’s inputs. This capacitor, working with the typical bridge component resistance, filters EMI and RFI. The filter’s corner frequency is nominally 265Hz.

Figure 1. A precision pressure sensor amplifier. It uses a remote current-driven PSA0701040 pressure sensor, a buffered OP177 precision operational amplifier, and an AD620 precision instrument amplifier set to a gain of 75.

Design and Integration Considerations

The PSA071040’s performance and durability are supported by several key design guidelines, which are critical regardless of the application:

• Differential Output Signal:
  The sensor produces a differential voltage output that accurately reflects both positive and negative pressure variations. This differential design is integral to achieving high linearity and stability in the output.
• Assembly Guidelines:
  • Thermal Management: Due to its small physical structure and limited thermal capacity, only the necessary heat should be used during the reflow process. Excess heat may alter sensor performance.
  • Port Protection: The sensor’s port, which leads to the sensing element, must be protected from debris. An acoustically transparent protective membrane is recommended to guard against foreign object damage.
  • Cleaning Practices: Post-reflow cleaning is discouraged to avoid damage. The use of “no-clean” solder paste is advised.
• Environmental Considerations:
  The sensor’s performance can be affected by external light sources and other environmental factors. It is important to ensure that the sensor is installed in an environment where these variables are controlled.
• Packaging:
  The PSA071040 is supplied in anti-static tubes, with 70 pieces per tube and 32 tubes per anti-static bag. This packaging format is optimized for high-volume manufacturing and automated pick-and-place processes.

Final Thoughts

The PSA071040 is a versatile MEMS pressure sensor engineered to support a range of applications, from medical devices to consumer electronics and Industrial systems. Its straightforward, differential voltage output and documented design guidelines provide engineers with a reliable tool for integrating precise pressure measurement into their systems.

For further technical details, refer to the official PSA071040 datasheet. Should you have any questions or require additional support, our engineering team is available to assist with design integration.