Flow Rate Sensor Disconnection Detection Circuit
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing flow rate sensors face challenges in accurately detecting disconnection between the resistance bridge circuit and the A/D converter, leading to deteriorated conversion accuracy and potential engine malfunctions, especially when dealing with small flow rates, due to the continuous detection current which does not account for fluctuations in current or resistance values.
Innovation Solution
A flow rate sensor design incorporating a switched capacitor type A/D converter with a disconnection detection circuit that utilizes a first capacitor connected to the input node of the A/D converter and a second capacitor to hold electric charge, detecting disconnection based on potential fluctuations, allowing for accurate detection without compromising the sensor's accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a disconnection detection circuit using continuous detection current is implemented, then disconnection detection capability is improved, but conversion accuracy of the A/D converter deteriorates due to current fluctuations and resistance variations
Solution Approach 1:
The detection current is supplied periodically rather than continuously. The periodical supply unit activates the detection current only during specific detection periods, allowing the A/D converter to perform normal high-precision conversions during other periods without interference from current fluctuations, thus resolving the contradiction between detection capability and conversion accuracy
Solution Approach 2:
Before normal A/D conversion operations, the system performs detection operations using the periodical detection current to check for disconnections. This preliminary detection ensures that subsequent measurement operations are not compromised by undetected disconnection issues, while the timing is arranged so detection does not interfere with measurement precision
2Reliability
If detection current always flows to detect disconnection, then disconnection detection is enabled, but fuel efficiency deteriorates due to continuous current consumption
Solution Approach 1:
The detection current flows periodically rather than continuously, being activated only during detection intervals. This reduces the overall energy consumption significantly compared to continuous current flow, while still maintaining the ability to detect disconnections at regular intervals, thus improving fuel efficiency without sacrificing detection capability
Solution Approach 2:
The control unit intelligently manages the detection current supply based on system needs, activating it only when disconnection detection is required. This self-regulating approach ensures energy is not wasted on continuous detection when the system is operating normally, thereby improving fuel efficiency while maintaining necessary detection functionality
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 approach enables reliable detection of wiring disconnections without reducing the accuracy of gas flow rate measurement, thereby improving the reliability of the flow rate sensor and maintaining efficient engine operation.
Implementation Method 1
The disconnection detection circuit includes a first capacitor and a detection unit. One connection portion of the first capacitor is connected to an input node of the A/D converter... A second capacitor (holding capacitance 144) that holds an electric charge of a potential in the first capacitor
Data Source
AI summary
In a flow rate sensor 10, a resistance bridge 100 detects a change in a gas flow rate. A differential A/D converter 122 converts an analog signal output from the resistance bridge 100 into a digital signal. A disconnection detection circuit 130 detects disconnection of bonding wires 164, 165 that connect the differential A/D converter 122 and the resistance bridge 100. The disconnection detection unit 130 includes a detection capacitance 141 and a comparator 145. One connection portion of the detection capacitance 141 is connected to an input node of the A/D converter 122. The comparator 145 detects the disconnection of the bonding wires 164, 165 based on a potential based on a ratio of an electrostatic capacitance of a P-side input capacitance 116 or a N-side input capacitance 117 to an electrostatic capacitance of the detection capacitance 141. The P-side input capacitance 116 and the N-side input capacitance 117 respectively are connected to operation input units of the differential A/D converter 122.