Flow Sensor Heater Circuit Calibration via Trimmable Resistor
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Solution Overview
Problem
Flow sensors face challenges in reducing size and increasing accuracy, particularly in maintaining a constant temperature delta between the heater and fluid for precise fluid flow measurement, which is affected by manufacturing variations and component tolerances.
Innovation Solution
A heater control circuit with a trimmable resistor and electronic switches that adapt the heater temperature by configuring between calibration and flow sensing modes, ensuring a predefined temperature delta is maintained through adjustments of the trimmable resistor, forming a balanced Wheatstone bridge configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the heater control circuit uses fixed resistance components, then the circuit design is simple, but manufacturing variations and component tolerances cause temperature delta drift reducing measurement accuracy
Solution Approach 1:
The patent applies the Dynamics principle by making the heater control circuit adjustable through electronic switches that can configure different resistance values in the heater control circuit. This allows the circuit to adapt to manufacturing variations and maintain accurate temperature delta calibration, resolving the contradiction between measurement precision and device complexity by providing adjustability without requiring a completely complex redesign
Solution Approach 2:
The patent applies the Parameter changes principle by enabling modification of the resistance parameters in the heater control circuit through electronic switches. The circuit can change its effective resistance values to compensate for manufacturing tolerances and maintain the predefined temperature delta, thereby improving flow measurement accuracy without excessive complexity
2Reliability
If the heater control circuit includes calibration components and switching mechanisms, then temperature delta accuracy is maintained, but the circuit complexity increases
Solution Approach 1:
The patent uses the Dynamics principle by incorporating electronic switches that can dynamically reconfigure the heater control circuit between calibration and normal operating modes. This dynamic switching capability allows the circuit to maintain reliable temperature delta consistency through calibration while managing complexity by using standard electronic switching components rather than more complex dedicated calibration mechanisms
Solution Approach 2:
The patent applies the Universality principle by designing the heater control circuit to perform multiple functions: normal heater control during flow measurement and self-calibration during calibration mode. The same circuit components and electronic switches serve both calibration and operational functions, improving reliability through consistent temperature delta maintenance while avoiding the need for separate dedicated calibration circuitry that would increase complexity
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 enhances the accuracy and reliability of fluid flow sensors by compensating for manufacturing variations and maintaining a consistent temperature delta, thereby improving the precision of flow measurements across various applications.
Implementation Method 1
a heater resistor disposed between the upstream flow sensor resistor and the downstream flow sensor resistor
Implementation Method 2
the first electronic switch is configured closed and provides a short circuit bypassing the third resistor when the heater control circuit is operated in a calibration mode
Data Source
AI summary
A heater control circuit in a fluid flow sensor. The circuit comprises first, second, and third resistors, a heater resistor, a trimmable resistor, and a switch. A positive terminal of the first resistor is connected to a positive terminal of the trimmable resistor, a negative terminal of the first resistor is connected to a positive terminal of the heater resistor, a negative terminal of the trimmable resistor is connected to a positive terminal of the second resistor, a negative terminal of the second resistor is connected to a positive terminal of the third resistor, and a negative terminal of the heater resistor is connected to a negative terminal of the third resistor, the terminals of the second resistor are attached to the terminals of the switch, where the switch is configured closed in a calibration mode and configured open in a flow sensing mode.