ASTM B539-20

Standard Test Methods for Measuring Resistance of Electrical Connections (Static Contacts)

SIGNIFICANCE AND USE
5.1 As stated in Terminology B542, contact resistance is comprised of a constriction resistance and a film resistance. When present, the latter of these is usually much greater in value and dominates the contact resistance. For a given contact spot, when the film resistance is zero or negligible the contact resistance for that spot is nearly the same as the constriction resistance and therefore, as a practical matter, has a minimum value which represents a clean metal-to-metal contact spot. As real contact surfaces exhibit varying degrees of roughness, real contacts are necessarily composed of many contact spots which are electrically parallel. In practical cases the clean metal-to-metal contact spots will carry most of the current and the total contact resistance is primarily dependent on the size and number of metallic contact spots present (see Note 1). In addition, acceptably low values of contact resistance are often obtained with true areas of contact being significantly less than the apparent contact area. This is the result of having a large number of small contact spots spread out over a relatively large apparent contact area.
Note 1: The term metallic contact as used here is intended to include the so called quasi-metallic contact spots as well. The latter case was discussed in Electric Contacts by Holm. 3  
5.2 The practical evaluation and comparison of electrical connections depend in large part on their contact resistance characteristics. On the one hand, the absolute value of contact resistance is greatly dependent on the size and distribution of the metallic conducting spots within the apparent area of load-bearing contact. On the other hand, a comparison of the initial resistance to the resistance after aging indicates how stable the system is in maintaining the initial contact area. Both of these characteristics should be considered when evaluating contact systems. The criteria employed in evaluating contact resistance and stability are not a par...
SCOPE
1.1 These test methods cover equipment and techniques for measuring the resistance of static electrical connections such as wire terminations or splices, friction connectors, soldered joints, and wrapped-wire connections.  
1.2 Measurements under two distinct levels of electrical loading are described. These levels are: (1) dry circuit, (2) and rated current. One or both of these levels of loading may be required in specific cases.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to become familiar with all hazards including those identified in the appropriate Safety Data Sheet (SDS) for this product/material as provided by the manufacturer, to establish appropriate safety, health, and environmental practices, and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Mar-2020
• ICS: 29.120.20 - Connecting devices
• Technical Committee: B02 - Nonferrous Metals and Alloys
• Drafting Committee: B02.05 - Precious Metals and Electrical Contact Materials and Test Methods

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: B539 − 20
Standard Test Methods for
Measuring Resistance of Electrical Connections (Static
1
Contacts)
This standard is issued under the fixed designation B539; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
3.1 Definitions:
1.1 These test methods cover equipment and techniques for
measuring the resistance of static electrical connections such as
3.1.1 See Terminology B542 for definitions of contact
wire terminations or splices, friction connectors, soldered resistance, film resistance, and constriction resistance.
joints, and wrapped-wire connections.
3.1.2 bulk resistance, n—the resistance a contact assembly
would have if it were solid metal of an identical geometry so
1.2 Measurements under two distinct levels of electrical
that the nominal contact area offered zero resistance. When
loading are described. These levels are: (1) dry circuit, (2) and
measuring contact resistance one attempts to include as little
rated current. One or both of these levels of loading may be
bulk resistance as possible in the measurement, by placing
required in specific cases.
measuring probes as close to the contact interface as practical.
1.3 This standard does not purport to address all of the
3.1.3 connection resistance, n—the resistance from the ter-
safety concerns, if any, associated with its use. It is the
mination point on one end of a device containing static
responsibility of the user of this standard to become familiar
contacts, through the contacts to the termination point on the
with all hazards including those identified in the appropriate
other end of the device. The termination point is the location on
Safety Data Sheet (SDS) for this product/material as provided
a terminal of a device where a wire or printed circuit path
by the manufacturer, to establish appropriate safety, health,
electrically connects to the terminal. This resistance is the
and environmental practices, and determine the applicability
value of resistance displayed by the device in a circuit
of regulatory limitations prior to use.
application.
1.4 This international standard was developed in accor-
3.1.3.1 Discussion—The term contact resistance is often
dance with internationally recognized principles on standard-
used in commercial literature to indicate the connection resis-
ization established in the Decision on Principles for the
tance displayed by the device in a standard application. In the
Development of International Standards, Guides and Recom-
more rigorous usage of contact resistance, the connection
mendations issued by the World Trade Organization Technical
resistance is the sum of the contact resistance plus the bulk
Barriers to Trade (TBT) Committee.
resistance of leads within the device that go to the static
contacts from the point that the leads are connected to the
2. Referenced Documents
external circuitry. Measurement of contact resistance indepen-
2
2.1 ASTM Standards:
dent of all bulk resistance is very difficult for most commercial
B542 Terminology Relating to Electrical Contacts and Their
devices.
Use
3.1.4 dry circuit, n—a circuit in which the open-circuit
E122 Practice for Calculating Sample Size to Estimate, With
voltage is less than or equal to 20 mV. Current is usually low
Specified Precision, the Average for a Characteristic of a
in a dry circuit, but a low-current circuit is not necessarily a
Lot or Process
dry circuit. When the applied voltage (open-circuit voltage) is
too low to cause any physical changes in the contact junction,
such as break-down of thin insulating films or softening of
1
These test methods are under the jurisdiction of ASTM Committee B02 on
contact asperities, the circuit is said to be a dry circuit.
Nonferrous Metals and Alloys and are the direct responsibility of Subcommittee
B02.05 on Precious Metals and Electrical Contact Materials and Test Methods.
3.1.5 open-circuit voltage, n—the steady-state voltage
Current edition approved April 1, 2020. Published April 2020. Originally
which would appear across the contacts if they were opened.
approved in 1970. Last previous edition approved in 2018 as B539 – 18. DOI:
10.1520/B0539-20.
3.1.6 static contacts, n—electric junctions designed for
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
infrequent separation and connection, and intended to perform
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
their
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: B539 − 18 B539 − 20
Standard Test Methods for
Measuring Resistance of Electrical Connections (Static
1
Contacts)
This standard is issued under the fixed designation B539; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 These test methods cover equipment and techniques for measuring the resistance of static electrical connections such as wire
terminations or splices, friction connectors, soldered joints, and wrapped-wire connections.
1.2 Measurements under two distinct levels of electrical loading are described. These levels are: (1) dry circuit, (2) and rated
current. One or both of these levels of loading may be required in specific cases.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to become familiar with all hazards including those identified in the appropriate Safety Data Sheet
(SDS) for this product/material as provided by the manufacturer, to establish appropriate safety, health, and environmental
practices, and determine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2
2.1 ASTM Standards:
B542 Terminology Relating to Electrical Contacts and Their Use
E122 Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot or
Process
3. Terminology
3.1 Definitions:
3.1.1 See Terminology B542 for definitions of contact resistance, film resistance, and constriction resistance.
3.1.2 bulk resistance, n—the resistance a contact assembly would have if it were solid metal of an identical geometry so that
the nominal contact area offered zero resistance. When measuring contact resistance one attempts to include as little bulk resistance
as possible in the measurement, by placing measuring probes as close to the contact interface as practical.
3.1.3 connection resistance, n—the resistance from the termination point on one end of a device containing static contacts,
through the contacts to the termination point on the other end of the device. The termination point is the location on a terminal
of a device where a wire or printed circuit path electrically connects to the terminal. This resistance is the value of resistance
displayed by the device in a circuit application.
3.1.3.1 Discussion—
The term contact resistance is often used in commercial literature to indicate the connection resistance displayed by the device in
a standard application. In the more rigorous usage of contact resistance, the connection resistance is the sum of the contact
1
These test methods are under the jurisdiction of ASTM Committee B02 on Nonferrous Metals and Alloys and are the direct responsibility of Subcommittee B02.11 on
Electrical Contact Test Methods.
Current edition approved Nov. 1, 2018April 1, 2020. Published December 2018April 2020. Originally approved in 1970. Last previous edition approved in 20132018 as
B539 – 02 (2013).B539 – 18. DOI: 10.1520/B0539-18.10.1520/B0539-20.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
B539 − 20
resistance plus the bulk resistance of leads within the device that go to the static contacts from the point that the leads are connected
to the external circuitry. Measurement of contact resistance independent of all bulk resistance is very difficult for most commercial
devices.
3.1.4 dry circuit, n—a circuit in which the open-circuit voltage is less than or equal to 20 mV. Current is usually low in a dry
circuit, but a low-current circuit is not necessarily a dry circuit. When the applied voltage (open-circuit v
...