Isolated-Output Test Probes for High Common-Mode Measurements

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing test and measurement instruments face challenges in high power device characterization due to safety concerns and limited isolation impedance under high voltage/high current switching conditions, particularly in scenarios involving high common mode signals.

Innovation Solution

A test and measurement system employing galvanic isolation techniques with an isolation barrier between the instrument and probe, utilizing optical or RF isolation to provide common mode rejection and safety advantages, enabling non-ground referenced measurements and eliminating ground-loop currents.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If magnetic coupling (transformers) is used for gate drive circuitry, then isolation is provided, but isolation impedance is limited and safety limitations exist

Engineering Contradiction:

Improveisolation impedanceVSAvoidsafety limitations

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

An isolation barrier is introduced as an intermediary component between the probe and the device under test. This barrier provides galvanic isolation through optical or RF coupling mechanisms, replacing the insufficient magnetic coupling of transformers. The isolation barrier acts as a mediator that transfers signals while maintaining high isolation impedance and eliminating direct electrical connection, thereby resolving the safety limitations and improving isolation performance.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the magnetic coupling mechanism (transformers) with optical or RF isolation techniques. This substitution eliminates the inherent limitations of magnetic coupling, such as limited isolation impedance and safety concerns. The optical/RF isolation provides superior galvanic isolation while maintaining signal integrity, directly addressing the technical contradictions regarding isolation performance and safety.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If probes with isolation techniques are used, then safety is improved and common mode rejection is achieved, but device complexity increases

Engineering Contradiction:

ImprovesafetyVSAvoidisolation barrier

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The isolation barrier is designed to perform multiple functions simultaneously: it provides galvanic isolation for safety, achieves common mode rejection for measurement accuracy, and enables non-ground referenced measurements. By consolidating these functions into a single component, the patent reduces overall system complexity while maintaining the required safety and performance levels.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Measurement precision

If galvanic isolation is implemented, then common mode rejection is improved and measurement accuracy is enhanced, but ease of operation is reduced

Engineering Contradiction:

Improvemeasurement accuracyVSAvoidoperation complexity

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The isolation barrier is designed to automatically handle common mode rejection and galvanic isolation without requiring manual intervention or complex configuration by the operator. The system self-adjusts to maintain measurement accuracy under high common mode signal conditions, thereby preserving ease of operation while achieving superior measurement precision.

Inventive Principle:

Principle #25Self-service

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

The system achieves high common-mode rejection and safety by ensuring complete galvanic isolation, enhancing measurement accuracy and signal fidelity while allowing measurements on large common-mode voltages.

Implementation Method 1

These probes provide galvanic isolation, e.g. using optical or RF isolation techniques, between a device under test (DUT) connected to an input of the probe and a test and measurement instrument connected to an output of the probe.

Methodology Applied

Scientific EffectOptical isolation: Optical Fibre

Implementation Method 2

Methodology Applied

Scientific EffectRF isolation: Electromagnetic Induction

Implementation Method 3

Methodology Applied

Scientific EffectGalvanic isolation: Electrical Resistance

Data Source

PatentUS20250321261A1Test and measurement instruments and probes having an isolated output

Publication Date: 2025.10.16 KEITHLEY INSTRUMENTS LLC

AI summary

The present disclosure describes a test and measurement system with a test and measurement instrument. In addition, the test and measurement system may include an isolation barrier providing galvanic isolation to the test and measurement instrument. The test and measurement system may include a circuit couplable to a device under test (DUT), where the circuit may include: a signal receiver configured to receive signals from the test and measurement instrument through the isolation barrier; an isolated power supply configured to power the circuit via the received signal; a signal generator configured to generate and output an isolated signal to the DUT using the isolated power supply; and a sensor for measuring output signals from the DUT in response to the isolated signal from the signal generator.