Buffered Miniature Pressure Sensor Arrays for Fast Scanning
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Solution Overview
Problem
Current miniature pressure scanners face challenges with long settling times for voltage spikes due to multiplexer characteristics and high source impedance, especially at higher ambient temperatures, which hinder fast sensor scanning in aerospace applications.
Innovation Solution
Incorporating a buffer configuration with transistors and bias resistors between sensor outputs and multiplexers to reduce output impedance, allowing for faster signal settling and improved multiplexing speeds, with options for integral or bare die elements on the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a multiplexer is used to scan multiple pressure sensors, then the device complexity is reduced, but the settling time increases due to charge injection and capacitance
Solution Approach 1:
A buffer circuit is introduced as an intermediary component between the pressure sensors and the multiplexer. This buffer acts as a mediator that isolates the sensor outputs from the multiplexer's charge injection and capacitance effects, allowing the multiplexer to switch channels without directly affecting the sensor signal integrity. The buffer's low output impedance enables it to drive the multiplexer input while maintaining stable sensor voltage levels.
2Productivity
If the multiplexer switching speed is increased, then the productivity improves, but the voltage spike settling time increases due to high source impedance
Solution Approach 1:
The buffer circuit changes the impedance parameter of the signal path. By providing a low output impedance buffer between the high-impedance sensor and the multiplexer, the circuit parameters are optimized to reduce voltage spike magnitude and accelerate settling time, enabling faster scanning speeds without sacrificing signal accuracy.
3Adaptability or versatility
If the ambient temperature is increased, then the operational range is extended, but the settling time increases due to temperature-dependent characteristics
Solution Approach 1:
The buffer circuit serves as a temperature-stable intermediary that compensates for temperature-dependent variations in sensor output impedance and multiplexer characteristics. By isolating the sensor from direct multiplexer interaction, the buffer maintains consistent signal levels across varying temperatures, preventing temperature-induced settling time increases.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The buffer configuration reduces output impedance by two orders of magnitude, enabling faster scanning rates and more accurate pressure readings, even at elevated temperatures, as demonstrated by improved oscilloscope traces and A/D count performance.
Implementation Method 1
each buffer configured to reduce the associated output impedance of the one sensor output coupled to it
Data Source
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AI summary
A miniature pressure scanning system includes a plurality of miniature pressure sensors where each pressure sensors includes at least one sensor output for providing an analog output signal indicative of a detected pressure on a body, and each pressure sensor output has an associated output impedance; a plurality of buffers, each buffer electrically connected to the output port of a corresponding one of the pressure sensors, and configured to reduce the associated output impedance of the corresponding sensor output coupled thereto, and further configured to provide at an output of the buffer the analog output pressure signal from the pressure sensor; and a multiplexer coupled downstream of the plurality of buffers and configured to multiplex the buffered analog output pressure signals to output a multiplexed analog signal representing the detected pressures.