Switch Matrix Guard Shorting for High Current
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Solution Overview
Problem
Conventional triaxial cables used in test and measurement systems exhibit high resistance and limited current capability, especially in high voltage applications, restricting the effectiveness of switching devices in high current applications.
Innovation Solution
The proposed solution involves a switch matrix design where the guard signal is shorted to the center conductor of each cable, eliminating the need for separate guard signals and connecting the outer shields together, which reduces path resistance and enhances current carrying capability while maintaining low leakage and high-speed pulsing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If triaxial cable is used in high voltage applications, then the cable can provide shielding and signal transmission, but the center conductor resistance becomes high which limits the maximum current capability
Solution Approach 1:
The patent merges the guard signal function into the center conductor by shorting the guard to the center conductor at the switching device. This combines the signal transmission and shielding functions into a single conductor path, eliminating the need for separate guard signals and reducing the effective resistance while maintaining shielding effectiveness through the outer shield and ground path.
Solution Approach 2:
The center conductor is made multi-functional by having it serve both as the signal transmission path and as the guard path. By shorting the guard to the center conductor, the same physical conductor performs multiple functions: carrying the force signal, providing the guard function, and maintaining the shielding effect, thereby increasing current capability without sacrificing reliability.
2Measurement precision
If separate guard signals are used in conventional switch matrices, then error currents can be minimized, but the path resistance increases and current carrying capability is limited
Solution Approach 1:
The patent combines the guard signal path with the center conductor path by implementing a short between the guard and center conductor at the switching device. This merging eliminates the separate guard signal transmission path, reducing the total path resistance while maintaining error current minimization through the preserved shielding effect of the outer shield and ground reference.
Solution Approach 2:
The patent extracts the guard signal function from the separate guard conductor and integrates it into the center conductor. By taking out the independent guard signal path and incorporating the guard function into the existing center conductor through a short, the system eliminates redundant conductors and reduces resistance while preserving the error current minimization benefit.
3Reliability
If conventional switch matrices with separate force and sense cables are used, then signal transmission is achieved, but the system complexity and cost increase
Solution Approach 1:
The patent makes the force cable center conductor multi-functional by enabling it to carry both the force signal and the guard function simultaneously through the guard-to-center-conductor short. This eliminates the need for separate sense cables and reduces the overall cable configuration complexity while maintaining reliable signal transmission through the preserved shielding and reference paths.
Solution Approach 2:
The patent merges the force cable and sense cable functions into a single cable configuration. By shorting the guard to the center conductor, the force cable alone can provide both the force signal transmission and the guard function that would traditionally require a separate sense cable, thereby reducing system complexity and cost while maintaining signal transmission reliability.
Data Source
AI summary
A test and measurement instrument switch matrix including a first cable including a center conductor and a guard connected to a first output of the test and measurement instrument; a second cable including a center conductor and a guard connected to a second output of the test and measurement instrument; a third cable including a center conductor and a guard connected to the device under test; and a fourth cable including a center conductor connected to the device under test and a guard connected to the device under test.