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:
- CPAP (continuous positive airway pressure) delivers a continuous level of air pressure,
- BiPAP (bi-level positive airway pressure) delivers different air pressures for inhalation and exhalation,
- 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)
- 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. This product family addresses the performance requirements of this market with a highly unique and differentiated offering:
- Incorporates both differential and gage pressure sensors in the same package.
- 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 – Highly Integrated Dual Sensor Solution
- 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 selected range
- Long term stability ±0.1% of FSS in first year
- Available in 3-port and 4-port configurations
- Output update rate up to 500Hz
- Advanced digital filtering (optional)
- Integrated closed loop control (optional)
- Temperature compensated from 5°C to 50°C
- Supply voltage compensation
- Fully integrated compensation math
- Standard I2C and SPI interfaces
Engineering Design Resources
3D Model & Configurator: CP Series
Select product from table to see the specs and order part number. In addition, view & download 3D Model in native CAD format.
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Getting Part Info…
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. Each pressure range is factory calibrated and optimized to ensure no degradation in 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 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:
- Design flexibility with ability to ‘tweak’ pressure range throughout development cycle
- Simplified product design with one sensor replacing up to 8 different sensors
- Ability to quickly develop product variants at different pressure ranges without changing hardware design
- Greater economies of scale by purchasing larger quantities of the same product
- Reduced manufacturing complexity and costs due to simplified calibration of sensors
- Up to 8x reduction in sensor inventory costs and product obsolescence
- Allows manufacturers to build fewer product variants, significantly lowering working capital requirements and inventory
Closed Loop Control adds capabilities to set and maintain flow rates via pressure management by directly controlling motors, valves and actuators. Superior 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 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:
- Greatly reduce loop delays to improve accuracy and responsiveness of your product
- Improve the reliability of your product by eliminating discrete parts
- Reduce your overall system costs
- Minimize system power and heat
- Simplify your product design
- Speed your time to market
Superior’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:
- 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.
- Eliminate noise sources such as fans and blowers before they reach the pressure sensing sub-system.
- Simplify product design with an integrated approach.
- 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:
- Flexibility with 3 modes of operation
- Lower system cost as need for an external pressure switch is eliminated
- Smaller overall PCB footprint
- Improve the reliability of your product by eliminating external components
- Minimize system power and heat
- Simplify your product design
- Speed your time to market
CPAP Application Video
CP Series Benefits Summary