ASTM F1681-07
(Test Method)Standard Test Method for Determining Current Carrying Capacity of a Conductor as Part of a Membrane Switch Circuit
Standard Test Method for Determining Current Carrying Capacity of a Conductor as Part of a Membrane Switch Circuit
SIGNIFICANCE AND USE
Current carrying capacity is used by designers and manufacturers of electronic interface circuitry to ensure that the membrane switch can reliably handle the loads occurring in normal use and under extreme circumstances. A thorough understanding of CCC allows manufacturers to take it into account when developing design rules for membrane switches.
Failures due to exceeding the CCC of a circuit may take the form of a significant change in conductor resistance, insulation breakdown (shorts), or conductor breakdown (opens).
Since a number of design parameters, such as trace width, ink film thickness, etc. affect the final test results, any conclusions should only be applied to specific designs, rather than to a general combination of materials.
Current carrying capacity tests may be destructive and units that have been tested should be considered unreliable for future use.
Current carrying capacity may be significantly different for static loads and dynamic (that is, cycling) loads. Failure modes are also generally different.
The use of a thermocouple to monitor the temperature of the UUT may be helpful to monitor the progress of the test.
Initial expected starting current should be calculated in advance to prevent damage to test equipment.
SCOPE
1.1 This test method covers the determination of the current carrying capacity of a conductor as part of a membrane switch.
1.2 This test method may be used to test a circuit to destruction, that is, to determine its maximum current carrying capacity, or it may be used to test the ability of a circuit to withstand a desired current level.
1.3 This test method applies only to static conditions, and does not apply to contact closure cycling of a membrane switch under current load (test method forthcoming).
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 establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
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Standards Content (Sample)
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Designation:F 1681–07
Standard Test Method for
Determining Current Carrying Capacity of a Conductor as
1
Part of a Membrane Switch Circuit
This standard is issued under the fixed designation F 1681; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.1 conductor resistance—the measured electrical resis-
tance through a circuit loop between two test points.
1.1 This test method covers the determination of the current
3.1.2 Discussion—When a switch is included in that loop, it
carrying capacity of a conductor as part of a membrane switch.
shall be 88closed” in accordance with Test Method F 1680.
1.2 This test method may be used to test a circuit to
3.1.3 current carrying capacity (CCC)—themaximumlevel
destruction, that is, to determine its maximum current carrying
of electrical current that a circuit can conduct without sustain-
capacity, or it may be used to test the ability of a circuit to
ing damage.
withstand a desired current level.
3.1.4 membrane switch—a momentary switching device in
1.3 This test method applies only to static conditions, and
which at least one contact is on, or made of, a flexible
doesnotapplytocontactclosurecyclingofamembraneswitch
substrate.
under current load (test method forthcoming).
3.1.5 power capacity—electrical power is defined as
1.4 This standard does not purport to address all of the
current 3 voltage = V 3 I (watts).
safety concerns, if any, associated with its use. It is the
3.1.6 test points—two preselected conductive points in a
responsibility of the user of this standard to establish appro-
circuit loop, possibly including a switch.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
4. Significance and Use
2. Referenced Documents 4.1 Current carrying capacity is used by designers and
2
manufacturers of electronic interface circuitry to ensure that
2.1 ASTM Standards:
the membrane switch can reliably handle the loads occurring in
F 1680 TestMethodforDeterminingCircuitResistanceofa
normal use and under extreme circumstances. A thorough
Membrane Switch
understanding of CCC allows manufacturers to take it into
3. Terminology account when developing design rules for membrane switches.
4.2 Failures due to exceeding the CCC of a circuit may take
3.1 Definitions:
the form of a significant change in conductor resistance,
insulation breakdown (shorts), or conductor breakdown
(opens).
1
This test method is under the jurisdiction of ASTM Committee F01 on
4.3 Since a number of design parameters, such as trace
Electronics and is the direct responsibility of Subcommittee F01.18 on Membrane
width, ink film thickness, etc. affect the final test results, any
Switches.
conclusions should only be applied to specific designs, rather
Current edition approved July 1, 2007. Published August 2007. Originally
approved in 1996. Last previous edition approved in 2002 as F 1681–96(2002).
than to a general combination of materials.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
4.4 Current carrying capacity tests may be destructive and
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
units that have been tested should be considered unreliable for
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. future use.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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F 1681–07
4.5 Current carrying capacity may be significantly different 8.2.3 Adjust the power supply to the next current level,
for static loads and dynamic (that is, cycling) loads. Failure dwell for 1 min and record the current, voltage (and tempera-
modes are also generally different. ture) as in 8.2.2. Repeat for each additional current level.
4.6 Theuseofathermocoupletomonitorthetemperatureof 8.2.4 If the test is intended to go to destruction, and no
the UUT may be helpful to monitor the progress of the test. degradation occurs at the maximum level, the test may be
4.7 Initial expected starting current should be calculated in repeated using a higher power (voltage and current) level, a
advance to prevent damage to test equipment. change in the voltage range is permissible.
8.2.5 At the conclusion of testing record the final results as
5. Interferences
in 8.2.2.
5.1 The following parameters may affect the results of this
test:
9. Calculations
5.1.1 Temperature,
9.1 Calculate power capacity (in watts) from CCC and test
5.1.2 Relative humidity, and
voltage
...
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