Remote Load Isolation Impedance Detection via Voltage Divider
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current Built In Test (BIT) techniques for aircraft systems lack the capability to measure remote load impedance, which is essential for ensuring lightning protection and continued airworthiness, as they cannot effectively detect degraded isolation impedance between load conductors and chassis ground during qualification testing.
Innovation Solution
A system and method that includes a remote load driven by a DC source with a controller having a positive sourcing driver interface, dedicated return legs, and impedance components configured to form a voltage divider, allowing for the detection of degraded isolation impedance by measuring voltage across high impedance pull-downs and identifying impedance degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current BIT techniques are used for aircraft sensor and actuator monitoring, then system reliability is maintained through redundancy and overdesign, but the capability to measure remote load impedance for lightning protection testing is lost
Solution Approach 1:
The controller's driver interface is designed to perform multiple functions: normal operation of remote loads and Built-In Test measurements. The same driver circuitry that controls actuators and sensors during flight operation is also used to measure remote load impedance, eliminating the need for separate dedicated test equipment and enabling both operational control and diagnostic measurement through a single integrated system
Solution Approach 2:
High impedance pull-down resistors are introduced as intermediary components between the driver output and ground. These resistors create a measurable voltage divider effect when remote load impedance degrades, allowing the controller to detect isolation impedance changes without directly interfacing with the high-impedance fault condition, thus enabling indirect measurement of remote load impedance
2Adaptability or versatility
If remote load impedance measurement capability is added to BIT, then lightning protection circuit testing is enabled, but device complexity increases
Solution Approach 1:
The driver interface is designed to perform multiple functions: normal operation of remote loads and Built-In Test measurements. The same driver circuitry that controls actuators and sensors during flight operation is also used to measure remote load impedance, eliminating the need for separate dedicated test equipment and enabling both operational control and diagnostic measurement through a single integrated system
Solution Approach 2:
The system uses its own existing resources for self-diagnosis. The controller's power supply, driver circuitry, and processing capabilities are used to perform the impedance measurement function, rather than requiring external test equipment. The high impedance pull-down resistors are integrated into the driver circuit, allowing the system to monitor its own health status using its operational components
3Difficulty of detecting and measuring
If high impedance pull-downs are used for voltage divider measurement, then degraded isolation impedance can be detected, but measurement precision requirements increase
Solution Approach 1:
The system changes the electrical parameters of the measurement circuit by using high impedance pull-down resistors (e.g., 100kΩ to 10MΩ) that match the expected range of remote load isolation impedance. This creates a voltage divider configuration where the voltage at the driver output changes measurably when isolation impedance degrades from mega-ohms to kilo-ohms, transforming an otherwise undetectable high-impedance fault into a measurable voltage variation that can be detected by the controller's existing analog-to-digital converters
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
Enables non-invasive measurement of load impedance, facilitating the detection of degraded isolation impedance, thereby ensuring system reliability and validating lightning protection circuits, ensuring correct functional testing and airworthiness.
Implementation Method 1
a first impedance operably connected between the output leg and ground, a second impedance operably connected between the dedicated return leg and a negative voltage supply
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Embodiments herein relate to a system and method (200) for detecting a degraded isolation impedance in a positively sourced remote load. The system includes a remote load driven by a direct current (DC) source, and a controller (100) operably connected to the remote load having a positive sourcing driver interface with a dedicated return having the DC source on an output leg (112) and a dedicated return leg (114). The positive sourcing driver also including a switching device (116) configured controllably connect a DC voltage supply to the output leg (112) of the DC voltage source, a first impedance (118) operably connected between the output leg (112) and ground, a second impedance (120) operably connected between the dedicated return leg (114) and a negative voltage supply, and a clamping and limiting device operably connected in series between the dedicated return leg and ground, the clamping device configured to limit a positive voltage on the return leg (114).