Wetting Current Control for Sensor Contact Switches
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Solution Overview
Problem
Devices for monitoring sensors with contact switches face challenges in ensuring that contacts are deoxidized without saturating the current source, particularly in the motor vehicle sector where voltage fluctuations occur, leading to inaccurate resistance measurements.
Innovation Solution
A method that regulates the wetting current by initially supplying a nominal current greater than the required wetting current, stopping and discharging the current source when the voltage exceeds a threshold, and gradually reducing the current to prevent saturation, using comparators to manage the discharging process and ensure the voltage remains below the threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a current source is used to supply wetting current to deoxidize contacts, then contact deoxidation is improved, but the current source may become saturated when voltage exceeds the supply voltage
Solution Approach 1:
The patent applies periodic action by implementing a control method that periodically monitors the voltage across switch/resistor assemblies and intermittently activates the current source. When voltage exceeds a threshold (indicating potential saturation), the current source is deactivated; when voltage is within acceptable range, the current source is activated to provide wetting current. This periodic on-off control prevents continuous saturation while ensuring adequate contact deoxidation occurs during active periods.
Solution Approach 2:
The patent implements feedback control by continuously monitoring the voltage across the switch/resistor assemblies and using this information to regulate the current source operation. The measured voltage is compared against threshold values, and the current source is adjusted accordingly - activated when voltage is low and deactivated when voltage approaches the supply voltage threshold. This closed-loop feedback mechanism dynamically prevents current source saturation while maintaining adequate wetting current for contact deoxidation.
2Use of energy by moving object
If the supply voltage is limited to 4-5 volts in stop and go vehicles, then energy consumption is reduced, but the voltage is insufficient to drive the current source effectively
Solution Approach 1:
The patent applies dynamics by making the current source operation dynamic rather than static. The current source is not continuously active at a fixed level but is dynamically controlled based on real-time voltage conditions. The control method adjusts the current source activation state (on/off) and duration based on the measured voltage across the switch/resistor assemblies, allowing the system to adapt its power consumption and drive capability to the available supply voltage conditions in stop-and-go vehicles.
Solution Approach 2:
The patent implements parameter changes by varying the operational parameters of the current source based on supply voltage conditions. When the supply voltage is limited to 4-5 volts, the control method modifies the current source activation timing and duration to optimize performance within these constraints. The voltage threshold for activation and deactivation is adjusted according to the available supply voltage, allowing the system to maintain effective contact deoxidation while adapting to reduced power availability.
3Device complexity
If a single-contact switch assembly with resistor is used to monitor sensor state, then circuit simplicity is improved, but measurement precision deteriorates due to voltage division errors
Solution Approach 1:
The patent applies partial or excessive action by providing a current source that can supply more current than the minimum required for wetting, allowing the system to overcome the limitations of the simple voltage divider configuration. By controlling the current source to provide adequate wetting current and then using feedback to prevent saturation, the system achieves both circuit simplicity and improved measurement precision. The controlled current ensures adequate signal levels for accurate measurement while preventing the voltage division errors that would occur with uncontrolled current.
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 method optimizes the wetting current to the maximum value that does not saturate the current source, ensuring accurate resistance measurements and preventing saturation of the analog-to-digital converter, allowing for precise determination of switch states in sensors.
Implementation Method 1
it is necessary, in this type of device, to ensure that the contacts are deoxidized
Implementation Method 2
a total capacitance of the corresponding cable
Data Source
AI summary
Disclosed is a method for optimizing a wetting current, for a device for monitoring sensors with contact switches including a current source and at least two switch/resistor assemblies (CT1/R1, CT2/R2) in parallel, including the following steps: the current source (A) supplies the circuit with a nominal current; if a voltage (Vm) measured across the terminals of the switch/resistor assemblies is greater than a threshold voltage (Vs), the threshold voltage being lower than the supply voltage of the current source and than the saturation voltage of the analog-to-digital converter (CAN), then the current source is stopped and a unit for discharging the circuit are implemented; and the current source supplies the circuit again with a supply current (Iwet_c) equal to the nominal current reduced by a predetermined increment. These two last steps are repeated until the measured voltage is lower than the threshold voltage.