ASTM F1681-96(2002)

Standard Test Method for Determining Current Carrying Capacity of a Conductor as Part of a Membrane Switch Circuit

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).
1.4 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

• Status: Historical
• Publication Date: 09-Feb-1996
• ICS: 19.080 - Electrical and electronic testing
• ICS: 29.120.40 - Switches
• Technical Committee: F01 - Electronics
• Drafting Committee: F01.18 - Printed Electronics

Relations

• Replaces: ASTM F1681-96 - Standard Test Method for Determining Current Carrying Capacity of a Conductor as Part of a Membrane Switch Circuit
• Effective Date: 10-Feb-1996
• Replaced By: ASTM F1681-07 - Standard Test Method for Determining Current Carrying Capacity of a Conductor as Part of a Membrane Switch Circuit
• Effective Date: 01-Jul-2007

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:F 1681–96 (Reapproved 2002)
Standard Test Method for
Determining Current Carrying Capacity of a Conductor as
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 3.1.6 test points—two preselected conductive points in a
circuit loop, possibly including a switch.
1.1 This test method covers the determination of the current
carrying capacity of a conductor as part of a membrane switch.
4. Significance and Use
1.2 This test method may be used to test a circuit to
4.1 Current carrying capacity is used by designers and
destruction, that is, to determine its maximum current carrying
manufacturers of electronic interface circuitry to ensure that
capacity, or it may be used to test the ability of a circuit to
the membrane switch can reliably handle the loads occurring in
withstand a desired current level.
normal use and under extreme circumstances. A thorough
1.3 This test method applies only to static conditions, and
understanding of CCC allows manufacturers to take it into
doesnotapplytocontactclosurecyclingofamembraneswitch
account when developing design rules for membrane switches.
under current load (test method forthcoming).
4.2 Failures due to exceeding the CCC of a circuit may take
1.4 This standard does not purport to address all of the
the form of a significant change in conductor resistance,
safety concerns, if any, associated with its use. It is the
insulation breakdown (shorts), or conductor breakdown
responsibility of the user of this standard to establish appro-
(opens).
priate safety and health practices and determine the applica-
4.3 Since a number of design parameters, such as trace
bility of regulatory limitations prior to use.
width, ink film thickness, etc. affect the final test results, any
2. Referenced Documents conclusions should only be applied to specific designs, rather
2 than to a general combination of materials.
2.1 ASTM Standards:
4.4 Current carrying capacity tests may be destructive and
F 1680 Test Method for Determining the Circuit Resistance
units that have been tested should be considered unreliable for
of a Membrane Switch
future use.
3. Terminology 4.5 Current carrying capacity may be significantly different
for static loads and dynamic (that is, cycling) loads. Failure
3.1 Definitions:
modes are also generally different.
3.1.1 conductor resistance—the measured electrical resis-
tance through a circuit loop between two test points.
5. Interferences
3.1.2 Discussion—When a switch is included in that loop, it
5.1 The following parameters may affect the results of this
shall be 88closed” in accordance with Test Method F 1680.
test:
3.1.3 current carrying capacity (CCC)—themaximumlevel
5.1.1 Temperature,
of electrical current that a circuit can conduct without sustain-
5.1.2 Relative humidity, and
ing damage.
5.1.3 Barometric pressure.
3.1.4 membrane switch—a momentary switching device in
which at least one contact is on, or made of, a flexible
6. Apparatus
substrate.
6.1 Suitable Device, providing a controlled voltage, capable
3.1.5 power capacity—electrical power is defined as
of supplying sufficient current for the range in question.
current 3 voltage = V 3 I (watts).
6.2 Suitable Meter(s), capable of measuring current and
resistance (with range appropriate to the test). Do not apply a
This test method is under the jurisdiction of ASTM Committee F01 on
voltage greater than the intended operating range of the circuit
Electronics and is the direct responsibility of Subcommittee F01.18 on Membrane
under test.
Switches.
6.3 Discreet Resistors, sufficient to provide at least 2 times
Current edition approved Feb. 10, 1996. Published April 1996.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
the current range desired for the test (at the preselected voltage
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
level) if the power supply current cannot be limited and
Standards volume information, refer to the standard’s Document Summary page on
measured directly. At the specified test voltage, the smallest
the ASTM website.
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F 1681–96 (2002)
resistor should correspond to twice the maximum current level 7.1.7.2 Set the power supply voltage to the desired level,
to be tested, or the anticipated failure range (if testing to and the current to the initial test level.
destruction). 7.2 In Process Test:
NOTE 1—A standardized selection of resistors may be used. To deter-
DISCREET RESISTOR METHOD
mine resistor values, see examples in Section 10.
7.2.1 Starting with largest resistor value (corresponding to
NOTE 2—The resistors must be of sufficient wattage to handle the
anticipated current/power loads. the lowest current level), insert the known resistor R into the
x
circuit.
6.4 Suitable Device, to apply a predetermined, repeatable
7.2.2 Turn on the power supply.
force in accordance with Test Method F 1680 to close the
7.2.3 Measure and record the actual current I through the
xa
switch (if a switch is part of the conductor circuit being tested).
circuit.
7.2.4 After either a predetermined time has passed, or when
7. Procedure
the current has stabilized, turn off the power supply.
7.1 Pre-Test Setup:
7.2.5 Record the length of time T for which power was
x
applied.
DISCREET RESISTOR METHOD
7.2.6 Comparetheactualcurrentlevel I tothepredicted I .
xa x
7.1.1 Measure and record the initial circuit resistance R of
i
If the two levels are significantly different, disconnect the
the circuit to be tested (if the circuit includes a switch, in
circuit, measure and record its resistance. Significant changes
accordance with Test Method F 1680).
in resistance or observable degradation, such as burning or
7.1.2 Based on the initial resistance R, the known resistors
i
discoloration of conductors, insulators or substrates are all
values R , and the desired test voltage level, calculate and
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