Choosing a Pressure Sensor

Transcription

1 Choosing a Pressure Sensor John Pocreva MannKind Corp #AdvMfgExpo

2 Introduction Consider a device to measure inhalation pressure through a dry powder inhaler Technology implemented in both Acoustic and Direct reading modes Original design was tabled in 2010 Project restarted in Early 2016 #AdvMfgExpo

3 Mannkind DPI Platform Unique high resistance dry powder inhaler Requires a minimal threshold for reliable operation Has multiple dosage strengths Reusable yet disposable inhaler, single use dose cartridges

4 Mannkind Inhaler Both the BluHale Device and Inhaler shown separately

5 MannKind Inhaler with BluHale Jacket attached

6 Mannkind BluHale Technology Device to measure and qualify patient inhalation effort Uses Bluetooth Low Energy to transmit an inhalation signal to a Phone, Tablet or PC Attaches to the disposable inhaler and is removed and reused

7 Mannkind Dreamboat Inhaler Inhaler with Demo Cartridge Demo Cartridge Installed

8 Typical Inhalation Profile

9 Android Profile Example

10 Electroacoustic Signal Path Mic HPF RMS- DC + - A/D RF/BLE UI CPU

11 Differential Pressure Signal Path Diff I2C CPU RF/BLE UI Pressure Abs Real Time OS LCD Display

12 Acoustic Measurements Uses a Microphone to sample sound pressure in the vicinity of the mouthpiece airway Is sensitive to variations in the airway Sensitive to ambient noise

13 How can we improve on this? We are trying to measure pressure Not sound Perhaps there is a pressure sensor that will work Google Search

14 Direct Pressure Measurements Starting with the MS5608 we attached SMT pressure sensors to the inhaler and ran tests Even in early trials the results were demonstrably better than acoustic pressure measurements

15 Pressure Sensor Specifications Part SDP31X MS5611 MS5805 Comm Protocol I2C I2C or SPI I2C Range 500Pa Diff mBar Absolute mbar Accuracy 3% mbar +- 2 mbar ADC 16 Bit 24 Bit 24 bit Conversion time 0.5 ms 8.2 ms ms

16 Analog or Digital? Analog Sensor would limit A/D resolution to 12 bits Digital Sensors would provide 16 and 24 Bit resolution plus noise immunity

17 0 to 6 kpa in 150ms Bandwidth This equates to a critical frequency of 40 Hz requiring a 25 ms sample interval

18 Accuracy Target final accuracy of 10% of reading Criteria for accuracy determination include known inhaler resistance and known pressure drop

19 Dynamic Range 0 to 6 kpa at the mouthpiece will equate to around 0 to 0.5kPa at the inlet A sensor that has at least a 500Pa range will suffice More is not necessarily better

20 Resolution The minimum pressure that can be resolved a function of both sensing technology and data conversion circuitry When all is said our resolution actually is about kpa

21 Strain gage Mass Flow Thermistor Pt RTD Sensing Technology

22 Physical Constraints BluHale Jacket Solid Model

23 1.Prototypes First test of the Absolute Variometer Sensor

24 First iteration with MS5611 Sensor The MS5608 Sensor installed for the first time.

25 2.Prototypes First test of the Absolute Variometer Sensor Variometer actually on main board model

26 MS5611 Barometric Pressure Sensor

27 3.Prototypes First test of the Absolute Variometer Sensor Variometer actually on main board model Uh oh, Variometer doesn t really work?

28 Variometer is too sensitive

29 4.Prototypes First test of the Absolute Variometer Sensor Variometer actually on main board model Uh oh, Variometer doesn t really work? Differential Mass Flow sensor

30 SDP31 Sensor

31 5.Prototypes First test of the Absolute Variometer Sensor Variometer actually on main board model Uh oh, Variometer doesn t really work? Differential Mass Flow sensor Variometer Differential Mass Flow combo

32 And what you have all been waiting for BluHale 3.0

33 6.Prototypes First test of the Absolute Variometer Sensor Variometer actually on main board model Uh oh, Variometer doesn t really work? Differential Mass Flow sensor Variometer Differential Mass Flow combo Yay! It finally works

34 Response Value Typical Response Curve BluHale Response y = x x R² = kpa

35 Acknowledgements Dennis Overfield Brendan Laurenzi Benoit Adamo Don Ridley Cindy Elliman Spencer Kinsey Chad Smutney Jason Van Anden