Measuring Electrical Contact Intermittences

B854: Standard Guide for Measuring Electrical Contact Intermittences

Electrical contact intermittences can be a silent killer of system reliability, leading to frustrating and costly failures in critical applications. For engineers striving to ensure robust performance, understanding and accurately measuring these transient circuit discontinuities is essential. ASTM B854 provides an authoritative framework for this crucial task, offering proven techniques to characterize and mitigate contact intermittences.

What is B854?

ASTM B854, "Standard Guide for Measuring Electrical Contact Intermittences," is an industry-leading document developed by ASTM International. It outlines standardized methods and considerations for detecting, quantifying, and characterizing brief disruptions in electrical circuits caused by contact behavior. Its primary purpose is to equip engineers with reliable procedures for evaluating the performance of electrical contacts under various conditions.

Scope & Purpose

This comprehensive guide focuses on measurement techniques applicable to electrical circuits that incorporate components such as slip rings, separable connectors, and electromechanical relays. It governs the assessment of circuit discontinuities, or intermittences, ranging in duration from approximately 10 nanoseconds to several seconds, provided they are significant enough to alter circuit function. While primarily intended for signal circuits (typically less than 100 mA), the standard acknowledges potential extensions to higher current applications, requiring user evaluation. It does not cover longer duration DC measurement methods or events shorter than nanosecond durations without specialized instrumentation.

Who Must Comply?

• • Primary Audience: Electrical Engineers, Test Engineers, Reliability Engineers, and Product Development Engineers.
• • Industries Affected: Electronics Manufacturing, Aerospace, Automotive, Telecommunications, and Industrial Equipment manufacturing.
• • Compliance Nature: Voluntary, but highly recommended for quality assurance and reliability-critical applications.
• • Enforcement: Compliance is typically driven by internal quality control, customer specifications, and industry best practices rather than direct regulatory enforcement.

Key Requirements Overview

Professionals utilizing ASTM B854 must ensure their measurement methodologies are robust and appropriate for the specific application. Key provisions include:

• • The standard requires a clear definition of what constitutes an intermittence for the intended application, considering resistance changes and time intervals.
• • Engineers must select appropriate apparatus and techniques based on the expected duration and magnitude of the intermittences to be detected.
• • Careful attention to cabling and shielding is mandated to prevent noise interference that could lead to false indications.
• • The guide emphasizes adapting general methods to specific circuit conditions and desired outcomes, ensuring test relevance.
• • Reporting of test results should be standardized and consistent with the capabilities of the measurement instrumentation used.

Related Standards & References

ASTM B854 complements other ASTM standards for a comprehensive approach to contact analysis. ASTM B542, "Terminology Relating to Electrical Contacts and Their Use," provides essential definitions. For static contacts, ASTM B539, "Test Methods for Measuring Resistance of Electrical Connections," offers complementary measurement capabilities. Furthermore, ASTM B615, "Practice for Measuring Electrical Contact Noise in Sliding Electrical Contacts," addresses a related phenomenon in different contact types, illustrating the interconnectedness of contact performance standards.