CPAP Pressure Sensors

Differential + Gage Dual Sensor Solution

Positive Airway Pressure

Positive airway pressure (PAP) treatment uses a machine to pump air under pressure into the airway of the lungs. This helps keep the windpipe open during sleep. There are three common types of PAP machines:

  1. CPAP (continuous positive airway pressure) delivers a continuous level of air pressure,
  2. BiPAP (bi-level positive airway pressure) delivers different air pressures for inhalation and exhalation,
  3. APAP (automatic positive airway pressure) delivers different pressure rates throughout your sleep, based on how you inhale.

There are many applications where PAP devices are used, including:

  • Sleep Apnea
  • COPD (chronic obstructive pulmonary disease)
  • Pre-term infants whose lungs are not fully developed
  • Respiratory failure (home ventilation devices)
  • Asthma
  • Pneumonia
  • OHS (obesity hypoventilation syndrome)
  • Pulmonary edema

CP Series Integrated Dual Pressure Sensor

Superior Sensor Technology has optimized the CP Series of highly integrated dual-sensor devices for PAP applications. Integrating a distinct differential pressure sensor and gage pressure sensor in one package, this product family provides a highly unique and differentiated offering:

  • Fully integrated dual sensor sub-system that simplifies product design and reduces overall system cost.
  • Available in shared 3-port and dedicated 4-port configurations for maximum design flexibility.
  • Highest levels of accuracy and performance due to the architecture’s extremely low noise floor.
  • Highly flexible and customizable solution as both sensors support multiple pressure ranges and each sensor has a selectable bandwidth filter.
  • Optional closed-loop control further simplifies design and increases overall system performance.
CP Series Product Matrix 2023-Q4
engineering - superior sensor tech

CP Series – Highly Integrated Dual Sensor Solution

CP Series Product Family

Family of sensors for CPAP, BiPAP and APAP

CP Table

New Product

CP202 and CP302

Integrated Closed Loop Control and Overpressure Indicator

An advanced development platform, the CP202/CP302 dual pressure sensors are designed to characterize and productize CPAP sensors with integrated closed-loop control. The sensors include programmable control parameters that are used for product development. These parameters are permanently stored in custom sensors.

For information about the CP202 and CP302 development platforms, download the CP Dev Kit Product Brief.

FEATURES (All CP Series products)

  • Highly integrated dual sensors with ADC and DSP
  • Combines differential and gage sensors in 1 device
  • 4 differential ranges per device (±250 Pa to ±2.5 kPa)
  • 4 gage ranges per device (±2 kPa to ±6 kPa)
  • Selectable bandwidth filter from 25Hz to 250Hz
  • Ultra low noise, 17.5 bit effective resolution
  • Very high accuracy ±0.05% of the selected range
  • Long-term stability ±0.1% of FSS in the first year
  • Available in 3-port and 4-port configurations
  • Output update rate up to 500Hz
  • Advanced digital filtering (optional)
  • Temperature compensated from 5°C to 50°C
  • Supply voltage compensation
  • Fully integrated compensation math
  • Standard I2C and SPI interfaces

Engineering Design Resources

CAD Design Files

3D Model & Configurator: CP Series

Select a product from the table to see the specs and order part number. In addition, view & download 3D Models in native CAD format.

(model download requires registration at CADENAS PARTsolutions)

90° Port Adapters

Depending on your product design, you may need the ports facing to the sides instead of the top. Superior offers highly reliable, high-quality adapters that plug into the two ports of our pressure sensors for easy implementation. With these 90° adapters, there is no need to worry about z-height.

90° adapters are available with and without o-rings:

KP-RAR: without o-rings

KP-ROR: with o-rings

Adapters are offered in packages of 50 and 1000.

Recommended NimbleSense Features for CP Series

Each CP device has two pressure sensors and both can support up to 4 different pressure ranges, with each range being factory-calibrated and optimized to maintain consistent total error band, accuracy, and stability. This alleviates the complexity and complications associated with working with multiple sensors. Utilizing a Multi-Range part streamlines both the design and manufacturing process, eliminating the need for researching, purchasing, and integrating numerous parts.

Implementing the same component in all designs enhances efficiency and ease, and pressure adjustments are conveniently controlled through a single software command. Moreover, Multi-Range provides the added benefit of a singular inventory item, adding value and convenience to manufacturing operations. In summary, the value of Multi-Range is apparent to both design and manufacturing teams alike.

CP Multi-Range Comparisons

Benefits of Multi-Range Technology include:

  1. Design flexibility with the ability to adjust pressure range throughout the development cycle
  2. Simplified product design with one sensor replacing up to 8 different sensors
  3. Ability to quickly develop product variants at different pressure ranges without changing hardware design
  4. Greater economies of scale by purchasing larger quantities of the same product
  5. Reduced manufacturing complexity and costs due to simplified calibration of sensors
  6. Up to 8x reduction in sensor inventory costs and product obsolescence
  7. Allows manufacturers to build fewer product variants, significantly lowering working capital requirements and inventory

By directly controlling motors, valves, and actuators, closed-loop control enhances the ability to establish and sustain flow rates through pressure management. Superior provides the option to integrate this capability into the sensor, allowing for more efficient control of flow rates and maintenance of flow rate targets.

Basic Control Loop System

Superior’s integrated closed-loop control design considerably reduces loop delays in electronic circuits by up to 100 times. This solution also removes the requirement to develop a complex, external control loop system, leading to more efficient, reliable, and cost-effective products. The benefits of an integrated closed-loop control cannot be overstated, especially in medical respiratory devices such as CPAP, HVAC systems, UAVs, and in products for measuring air quality.

Displayed in the diagram below is a block layout depicting the implementation of a superior closed-loop control system for an air quality application. For accurate measurement of air quality, it is essential to uphold a steady and predetermined airflow through the viewing window. The differential pressure measured across the venturi serves as a direct indication of the flow entering the viewing window. By setting a target pressure level across the venturi, the differential pressure sensor automatically adjusts the pump drive, up or down, to maintain the aimed differential pressure and sustain an even airflow into the viewing window. The utilization of the NimbleSense closed loop circuit, in combination with the company’s exclusive noise filtering technology, successfully reduced loop delay by more than 100 times.

CLC flow

Benefits of the integrated closed-loop control include:

  1. Greatly reduce loop delays to improve the accuracy and responsiveness of your product
  2. Improve the reliability of your product by eliminating discrete parts
  3. Reduce your overall system costs
  4. Minimize system power and heat
  5. Simplify your product design
  6. Speed your time to market

Superior’s cutting-edge digital filter is a multi-order filter that leverages advanced filtering capabilities at the front end of the sub-system to eradicate critical noise caused by fans, blowers, or other dry air/gas sources before they reach the pressure-sensing sub-system. This is accomplished using the NimbleSense advanced filtering capability, which eliminates sensor-induced mechanical noise before it becomes an error signal that can negatively impact overall system performance. By replacing a competing component in customer deployments, our sensor has produced a more than 10-fold reduction in sensor-induced noise, significantly enhancing the SNR of the sensor output. This improvement is even more substantial in very low-pressure systems.

By incorporating both standard and optional digital filters, this feature offers considerably better noise reduction and eliminates the need to design an external filtering system, leading to more efficient, reliable, and cost-effective products. Our advanced digital filtering is fine-tuned for each application to ensure that mixed sampling noise is well below the noise floor. By eradicating mechanical noise, we maximize the overall performance of the system.

Below is an example of a 4th-order FIR filter that has been specifically designed to eliminate pump noise above 50 Hz, which has an equal magnitude of noise as the signal being monitored. The graphs illustrate the outcome of Superior’s advanced digital filter.

Updated ADF transfer

Benefits of the advanced digital filtering technology include:

  1. Greatly reduced system noise levels by 10x or more, especially important in very low pressure applications. For noise prone systems, an improvement of 100x to 1000x is not unreasonable.
  2. Eliminate noise sources such as fans and blowers before they reach the pressure sensing sub-system.
  3. Simplify product design with an integrated approach.
  4. Speed time to market by not having to design an external filtering system.

A pressure switch is a mechanical or electronic device that is activated when a certain pressure threshold or set point is reached. These failsafe response components instruct the system to perform an action if a certain pressure threshold is met.

Types of Pressure Switches

Fixed Pressure Switches

As their name implies, fixed pressure switches have pre-set, non-changeable pressure thresholds that are set by the pressure switch manufacturer. The device maker receives the pressure switch already configured and cannot change values. Examples where fixed pressure switches are common are certain types of medical devices, such as ventilators.

Variable Pressure Switches

With variable pressure switches, the threshold value can be set either by the device maker or dynamically in the field. If it is controlled by the device maker, when they build their product they select certain resistor pairs that control the voltage input that determines the threshold. Once they build the product, the threshold value cannot be changed.

In cases where the threshold can be set in the field, this is typically done via software or a mechanical knob/switch. In this scenario, the pressure switch is usually not implemented as a safety feature. A good example is with air filters – where depending on the system implementation, the threshold value needs to be adjusted to account for any head loss in the flow stream.

Superior’s pressure switch changes state depending on the measured pressure being above or below a certain threshold. This can be used as a fast response failsafe feature for overpressure conditions, and to provide other simplified on/off system feedback. However, unlike other more common pressure switches, the Superior Sensor pressure switch includes three modes for setting threshold pressure, one fixed and two variable:

  • Fixed mode: Superior Sensor Technology sets the threshold and provides the ‘ready for use’ configured sensor (with integrated pressure switch) to the device manufacturer.
  • Variable mode 1: The device manufacturer can configure and set the proper thresholds at the time of product manufacturing.
  • Variable mode 2: Pressure thresholds are field programmable via software, so the pressure switch can be ‘tuned’ after product manufacture depending on the use case.

Benefits of Superior’s integrated pressure switch include:

  1. Flexibility with 3 modes of operation
  2. Lower system cost as the need for an external pressure switch is eliminated
  3. Smaller overall PCB footprint
  4. Improve the reliability of your product by eliminating external components
  5. Minimize system power and heat
  6. Simplify your product design
  7. Speed your time to market

Video Corner

CPAP Application Video

CP Series Benefits Summary