Digital Thermal Air Flow Sensor With Onboard Calibration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing air flow sensors in test and measurement instruments require individual calibration and are not easily interchangeable between instruments, leading to increased manufacturing and maintenance costs due to their specific calibration-dependent configurations.
Innovation Solution
A standalone digital air flow sensor with a microcontroller that uses digitally controlled PWM signals to drive the sensor element, performing continuous signal processing and storing calibration data internally, allowing for a self-contained, interchangeable, and easily connectable solution with a digital interface (SPI) to measurement instruments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If individual calibration is performed for each sensor element, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The sensor element performs self-calibration by storing calibration data internally in non-volatile memory. The microcontroller automatically retrieves and applies calibration factors without requiring external calibration equipment or procedures, enabling the sensor to service its own calibration needs while maintaining measurement precision.
Solution Approach 2:
The sensor design incorporates a universal calibration data structure that can accommodate multiple sensor elements with different characteristics. The same sensor module can be used across different measurement instruments without recalibration, as the calibration data is embedded within each sensor element and automatically recognized by any compatible instrument.
2Measurement precision
If sensors are calibrated to individual instruments, then measurement precision is improved, but ease of operation deteriorates due to inability to interchange sensors
Solution Approach 1:
The sensor element is designed as a universal component that can be interchangeably connected to multiple measurement instruments without requiring recalibration. Each sensor contains its own calibration data, making it compatible with any instrument that supports the standardized interface, thereby improving ease of operation while preserving measurement precision.
Solution Approach 2:
Calibration data is pre-stored in the sensor element during manufacturing before the sensor is deployed. This preliminary calibration action eliminates the need for field recalibration when sensors are moved between instruments, allowing users to simply connect and use the sensor without additional calibration steps.
3Ease of manufacture
If analog control loops are used to drive sensor bridges, then manufacturing simplicity is improved, but measurement precision and signal processing capability deteriorate
Solution Approach 1:
The patent replaces analog control loops with a digitally controlled PWM system. The microcontroller generates PWM signals to drive the sensor bridge, and digital signal processing is used to process the output. This substitution of digital for analog systems improves measurement precision and signal processing capability while maintaining ease of manufacture through standardized digital components.
Solution Approach 2:
The system changes the control parameter from continuous analog voltage to digital PWM duty cycle. This parameter change enables precise control of the sensor bridge while allowing digital processing of the measurement signal, improving both precision and flexibility without significantly complicating the manufacturing process.
4Ease of operation
If sensors are made interchangeable without recalibration, then ease of operation is improved, but manufacturing precision requirements increase
Solution Approach 1:
Each sensor element is equipped with self-calibration capabilities through embedded calibration data stored in non-volatile memory. During manufacturing, precise calibration measurements are performed and the results are permanently stored in each sensor. This self-service calibration approach allows sensors to be manufactured with standard precision while maintaining interchangeability, as each sensor carries its own calibration information rather than requiring the instrument to be calibrated to the sensor.
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
This solution reduces manufacturing and maintenance costs by enabling easy interchangeability of sensors without recalibration, simplifies interfacing with test instruments, and provides accurate air velocity and temperature readings through onboard processing, reducing the complexity of the measurement instrument and accommodating various measurement applications.
Implementation Method 1
thermal anemometers with an analog interface between the sensor element and the instrument
Data Source
AI summary
An air flow sensor includes a sensor element and a microcontroller, employing a PWM signal to drive the sensor element. Signals from the sensor element are processed by the microcontroller inside the sensor, resulting in continuous readings of air velocity and air temperature.