The Industry’s Most Advanced Pressure Sensing System
The Technology Behind Superior’s Pressure Sensors
Traditional Piezoresistive MEMS Pressure Sensors
Piezoresistive microelectromechanical (MEMS) pressure sensors combine piezoresistive sensing with MEMS design and processing to create one of the most dominant and useful pressure sensing/measuring techniques. Additional circuitry has always been required to make the sensor’s output useful for measurements or control. However, major enhancements to this core pressure sensing technique were required to create Superior Sensor Technology’s advanced pressure sensing system (APSS).
Piezoresistive MEMS pressure sensors are mass produced by etching or micromachining hundreds of thin pressure sensitive diaphragms (membranes) from a silicon wafer. Integrated circuit (IC) processing is used to form four piezoresistive (pressure sensitive resistor) sensors on the surface of the silicon wafer for each etched diaphragm creating an integrated piezoresistive pressure sensor. The design of the diaphragm and the piezoresistors, including their location and configuration, normally determines the useful range of the pressure sensor. Connecting the four resistors to form a Wheatstone bridge allows the measurement of very small changes in resistance due to the strain on the diaphragm and translate the changes into an output voltage. Three elements, the etched diaphragm, four piezoresistors and a Wheatstone bridge configuration, provide the basis or core of piezoresistive MEMS pressure sensors.
To provide the digital interface and make the piezoresistive MEMS pressure sensor useful and achieve the temperature stability, zero and full-scale calibration accuracy required in target applications, additional circuitry is required. This circuitry is commonly implemented at the sensor packaging level in many traditional sensors. Unfortunately, the traditional pressure sensor approach lacks the performance required for many demanding applications. This necessitates that customers add their own custom hardware and software to achieve their design goals. Superior Sensor Technology’s NimbleSense™ architecture builds on the traditional pressure design to provide a higher-performance, application-specific solution.
NimbleSense – The Superior Architecture for Sensing Pressure
Using Superior Sensor Technology’s proprietary NimbleSense architecture allows highly differentiated advanced pressure sensing systems to be created from a design toolbox of technology building blocks, greatly improving system performance in the end application, while providing enhanced features and cost-optimized manufacturing solutions. We call this fully integrated platform the industry’s first System-in-a-Sensor.
The NimbleSense architecture incorporates processing intelligence with signal path integration and proprietary algorithms to provide sensor sub-system integration with maximized sensor performance. Choosing from a smorgasbord of proven and tested building blocks, Superior Sensor Technology design experts integrate the appropriate blocks into a pressure sensor sub-system to achieve optimized performance for the customer’s application requirements.
These different pieces provide significant design flexibility to satisfy customer goals. With these highly-integrated subsystems, a user can quickly and easily develop the pressure sensing solution required in their specific end product by simply adding a few low-cost external components. The plethora of technology building blocks in the NimbleSense architecture enables a 5 to 10x performance increase as well as a variety of application-specific features.
Technology Building Blocks
Flexibility is at the core of the NimbleSense architecture and the System-in-a-Sensor approach. This unique technology allows you to quickly prototype and design the sensor into your product, support multiple product lines with one particular sensor, add new capabilities and application specific features and reduce system cost through lower component count and greater product reliability. Based heavily on customer feedback, the Superior Sensor Technology engineering team is constantly innovating and introducing new building blocks in the NimbleSense architecture.
One device can support up to 8 different pressure ranges, and each pressure range is factory calibrated and optimized ensuring no degradation in a total error band, accuracy or stability regardless of the range selected. This eliminates the complexity and headaches of working with multiple sensors.
Instead of having to research, purchase and design-in multiple parts, a single Multi-Range part simplifies both the design and manufacturing of a product. Designing in the same part throughout your designs is much more efficient than having to select multiple components. When you design in each of the Superior Sensor pressure sensors, the setting of the pressure is done via a single software command. It’s that simple. Add the fact that there is only one product to inventory, and your manufacturing team will also appreciate the value of Multi-Range!
Benefits of Multi-Range Technology include:
To ensure the utmost accuracy in medical devices, the company has developed its proprietary Z-Track technology that virtually eliminates zero drift. Zero error reduction is critical in medical devices such as Spirometers, where an inaccurate reading can have life changing consequences.
Z-Track provides greater accuracy to devices such as spirometers, resulting in more effective diagnosis and better treatment plans. As you can see from the figure, Z-Track maintains minimal zero-point deviation with results that are consistent regardless of elapsed time. When combined with the Superior Sensor’s position insensitivity capability, the company’s pressure sensors provide the most accurate readings for all types of spirometry equipment including handheld and desktop units. Not only are you certain that the device has virtually eliminated all zero errors, but you can be sure of accurate readings regardless of how the spirometer is positioned or used.
Benefits of Z-Track Technology include:
Closed Loop Control adds capabilities to set and maintain flow rates via pressure management by directly controlling motors, valves and actuators. Superior Sensors offers the option to have this capability integrated into the sensor in order to more effectively set and maintain flow rates by directly controlling motors, valves and actuators to maintain flow rate targets.
The integrated Closed Loop Control design significantly reduces loop delays in the electronic circuit by up to 100x. This integrated solution also eliminates the need to design and implement a complex control loop system, resulting in more efficient, more reliable and less costly products. Closed Loop Control is of extreme value in medical respiratory devices such as ventilators and CPAP, as well as in air quality measurement products.
The figure below shows a block diagram of an implementation of the Superior Sensor Closed Loop Control for an air quality application. In order to effectively measure the air quality, we require maintaining a constant/known airflow through the viewing window. The differential pressure across the venturi directly measures the flow into this viewing window. The system sets a target pressure level across the venturi and the differential pressure sensor automatically increases or decreases the drive to the pump to maintain the targeted differential pressure, ensuring a constant airflow into the viewing window. This is accomplished with the NimbleSense closed loop circuit used in combination with the company’s proprietary noise filtering, resulting in greater than 100x reduction in loop delay.
Benefits of the integrated Closed Loop Control include:
Superior Sensor’s advanced digital filter is a multi-order filter that utilizes advanced filtering capabilities on the front-end of the sub-system to eliminate critical noise created by fans, blowers or other dry air/gas sources prior to reaching the pressure sensing sub-system. The NimbleSense advanced filtering capability removes sensor induced mechanical noise before it becomes an error signal that can adversely impact overall system performance. In customer deployments where our sensor replaced a competing component, we have seen greater than 10x reduction in sensor induced noise, thus greatly improving the SNR of the sensor output. In very low pressure systems, the improvement is even more significant.
Incorporating both standard and optional digital filters, this feature provides significantly better noise reduction and eliminates the need to design an external filtering system, resulting in more efficient, more reliable and less costly products. Our advanced digital filtering is optimized for each application to ensure mixed sampling noise is kept well below the noise floor. By removing the mechanical noise, we maximize overall system performance.
The example below is of a 4th order FIR filter customized to block pump noise above 50 Hz, which has noise of equal magnitude as the signal of interest. The lower graphs show the resulting impact of the advanced digital filtering.
Benefits of the advanced digital filtering technology include:
As all of Superior’s pressure sensors have an extremely low noise floor, theoretically power line interference can be ‘heard’ when taking measurements. The integrated 50Hz/60Hz notch filter eliminates this noise so you maintain the advantage of having such a low noise floor pressure sensor without any external interference. With the notch filter seamlessly integrated in the pressure sensor module, the sensor blocks out the interference caused by these frequencies before it reaches the user application. Further, as the notch filter is internal to the sensor module, it eliminates the need for an engineer to design and implement an external notch filter. This feature removes an external notch filter, so the overall system is more efficient, more reliable and less costly.
Benefits of the integrated 50/60Hz Notch Filter include:
With such a high demand for ventilators, it is critical that they continue to work without interruption. Eliminating failures before they become system alarms is a must. Implemented in close collaboration with partners, Superior Sensor’s proprietary Self Aware technology offers a capability that ensures maximum uptime and overall reliability.
Self Aware sensor technology tracks changes in error levels. By being part of a redundant system, the technology both eliminates a single point of failure service interruption and reduces false positives with respect to error notifications. Self Aware can reduce pressure sensor related alarm rates by up to 1000x.
If Self Aware technology is beneficial for your application, please contact us to discuss how we can implement this innovative feature to help differentiate your product.
Application examples enabled by the NimbleSense architecture’s building block approach include:
HVAC DPT: Multi-Range, 50/60 Hz Notch Filter
Spirometry: Z-Track, Proprietary Zero-Noise Suppression
Air Quality: Advanced Digital Filtering, Closed Loop Control
CPAP/BiPAP: Advanced Digital Filtering, Closed Loop Control
Industrial: Advanced Digital Filtering, Multi-Range, 50/60 Hz Notch Filter
Benefits of NimbleSense Architecture:
Starting Your Next Design with Superior Sensor Technology
To take advantage of the newest approach to pressure sensing systems technology for your next design, Contact us or ask your local distributor for contact information.
NimbleSense, Multi-Range, Z-Track and Self-Aware are trademarks of Superior Sensor Technology.
Optimized for CPAP, BiPAP and APAP
Used for many applications including sleep apnea, COPD, asthma and home ventilators, the CP Series includes 2 pressure sensors in one device. A gage sensor measures patient airway pressure and a differential for system flow measurement. This dual sensor solution eliminates the need for a second physical sensor. This simplifies design, speeds time to market, reduces PCB space and lowers system costs. The CP Series is highly flexible with 64 possible configurations, a very fast 2 msec response time and market leading accuracy.
Flexible Application Support
The market’s only solution supporting many industrial applications and pressure ranges with one sensor. Available to measure differential, gage and absolute pressures, the ND series enhances a long list of manufacturing, research and development, and commercial applications with up to 7 system optimized Multi-Range pressure ranges from 62.5 Pa to 10.3 Bar (0.25 inH20 to 150 psi), selectable bandwidth filter from 1 Hz to 200 Hz and an integrated 50/60 Hz notch filter to provide the industry’s lowest noise floor.
Optimized for Air Handling Applications
The industry’s first Pressure Sensor solution optimized for Air Handling (HVAC, VAV, etc) solutions. With Multi-Range support a single HV device can replace up to 8 competing, single range devices while improving system performance at each range. Offering user selectable pressure ranges that can be modified ‘on the fly,’ the HV Series minimizes variants to support the demanding functional requirements of the HVAC market.
Designed for Pulmonary Functional Testing
(Spirometry, FOT, etc.)
The SP Series employs NimbleSense architecture to achieve very high dynamic range and create the industry’s highest performing Spirometry pressure sensing devices. These sensors utilize Multi-Range technology to offer up to 4 system optimized pressure ranges from 250 Pa to 40k Pa. Providing the industry’s lowest noise floor, features include selectable bandwidth filter from 25 Hz to 250 Hz and proprietary Z-Track technology that virtually eliminates zero drift.
Differential Pressure Transmitter Sub-System
This highly integrated hardware and software pressure sensing solution gives the customer the ultimate in flexibility and performance for their Differential Pressure Transmitter systems. Adding analog interfaces with easy to use configuration software, customers can now greatly accelerate their product definition and engineering development efforts while simplifying system calibration testing in manufacturing.
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