1、Designation: F 1681 07aStandard Test Method forDetermining Current Carrying Capacity of a Conductor asPart of a Membrane Switch Circuit1This standard is issued under the fixed designation F 1681; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the currentcarrying capacity of a conductor as
3、part of a membrane switch.1.2 This test method may be used to test a circuit todestruction, that is, to determine its maximum current carryingcapacity, or it may be used to test the ability of a circuit towithstand a desired current level.1.3 This test method applies only to static conditions, anddo
4、es not apply to contact closure cycling of a membrane switchunder current load (test method forthcoming).1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and
5、 health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2F 1578 Practice for Contact Closure Cycling of a Mem-brane SwitchF 1680 Test Method for Determining Circuit Resistance of aMembrane Switch3. Terminology3.1 Definitions
6、:3.1.1 conductor resistancethe measured electrical resis-tance through a circuit loop between two test points.3.1.2 DiscussionWhen a switch is included in that loop, itshall be 88closed” in accordance with Test Method F 1680.3.1.3 current carrying capacity (CCC)the maximum levelof electrical current
7、 that a circuit can conduct without sustain-ing damage.3.1.4 membrane switcha momentary switching device inwhich at least one contact is on, or made of, a flexiblesubstrate.3.1.5 power capacityelectrical power is defined ascurrent 3 voltage = V 3 I (watts).3.1.6 test pointstwo preselected conductive
8、 points in acircuit loop, possibly including a switch.4. Significance and Use4.1 Current carrying capacity is used by designers andmanufacturers of electronic interface circuitry to ensure thatthe membrane switch can reliably handle the loads occurring innormal use and under extreme circumstances. A
9、 thoroughunderstanding of CCC allows manufacturers to take it intoaccount when developing design rules for membrane switches.4.2 Failures due to exceeding the CCC of a circuit may takethe form of a significant change in conductor resistance,insulation breakdown (shorts), or conductor breakdown(opens
10、).4.3 Since a number of design parameters, such as tracewidth, ink film thickness, etc. affect the final test results, anyconclusions should only be applied to specific designs, ratherthan to a general combination of materials.4.4 Current carrying capacity tests may be destructive andunits that have
11、 been tested should be considered unreliable forfuture use.4.5 Current carrying capacity may be significantly differentfor static loads and dynamic (that is, cycling) loads. Failuremodes are also generally different.4.6 The use of a thermocouple to monitor the temperature ofthe UUT may be helpful to
12、 monitor the progress of the test.1This test method is under the jurisdiction of ASTM Committee F01 onElectronics and is the direct responsibility of Subcommittee F01.18 on MembraneSwitches.Current edition approved Dec. 1, 2007. Published December 2007. Originallyapproved in 1996. Last previous edit
13、ion approved in 2007 as F 168107.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM Internationa
14、l, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.7 Initial expected starting current should be calculated inadvance to prevent damage to test equipment.5. Interferences5.1 The following parameters may affect the results of thistest:5.1.1 Temperature,5.1.2 Rela
15、tive humidity, and5.1.3 Barometric pressure.6. Hazard6.1 The user must be aware of the operating range of theirequipment to prevent damage to the device from overloadduring testing. For example, the current should be adjustedstarting from a minimum setting, and a decade box should starton the highes
16、t rating.7. Apparatus7.1 Controlled current and voltage source, capable of sup-plying sufficient current for the range in question.7.2 Suitable Meter(s), capable of measuring current andresistance (with range appropriate to the test). Do not apply avoltage greater than the intended operating range o
17、f the circuitunder test.7.3 Suitable Device, to apply a consistent, repeatable forcewith an elastomeric probe in accordance with Test MethodF 1578 to close the switch (if a switch is part of the conductorcircuit being tested).7.3.1 Since the switch may heat up during the test it isadvisable to use a
18、 mechanical device instead of a human fingerto close the switch.8. Procedure8.1 Pre-Test Setup:8.1.1 Turn on the power supply; set the power supplyvoltage to the specified operating level and the current to theinitial zero test level.8.2 In Process Test:8.2.1 With the power supply turned off connect
19、 the testspecimen to the power supply.8.2.1.1 If the specimen includes a switch close the switch inaccordance with F 1680.8.2.2 Turn on the power supply and adjust the current to theinitial test level. After 1 min record the actual current throughthe circuit and record the applied voltage. If a ther
20、mocouple isused record the temperature at the end of each level. Recordvisual observations. Record the resistance value of the speci-men (with the power supply off) or by calculation (using a voltmeter across the specimen).8.2.3 Adjust the power supply to the next current level,dwell for 1 min and r
21、ecord the current, voltage and visualobservations (and temperature when applicable) as in 8.2.2.Repeat for each additional current level.8.2.4 If the test is intended to go to destruction, and nodegradation occurs at the maximum level, the test may berepeated using a higher power (voltage and curren
22、t) level, achange in the voltage range is permissible.8.2.5 At the conclusion of testing record the final results asin 8.2.2.9. Calculations9.1 Calculate power capacity (in watts) from CCC and testvoltage V as follows:P 5 CCC 3 V.10. Report10.1 Report the following information:10.1.1 Description and
23、 specifications of all apparatus,10.1.2 Date of test,10.1.3 Person performing test,10.1.4 Ambient Temperature,10.1.5 Relative humidity,10.1.6 Barometric pressure,10.1.7 Test voltage (dc, ac, ac-r/min, etc.),10.1.8 Test type (destructive or specified range),10.1.9 Part number, revision level and desc
24、ription of partunder test,10.1.10 Description of test points and connection,10.1.11 Description of device and method used to closeswitch (if applicable),10.1.12 For each test cycle at a different current level, reportthe following:10.1.12.1 Current and voltage values,10.1.12.2 Description of any vis
25、ual or resistance changesobserved, and10.1.12.3 The user interface temperature (thermocouple), ifmeasured.10.1.13 At the conclusion of the test, report either the CCC(that is, the maximum) or whether the circuit was able tomaintain the current without discoloration or change of resis-tance less than
26、 the specified amount (at the desired voltage andcurrent level) or without exceeding a temperature of 60C atthe user interface.11. Precision and Bias11.1 The precision and bias of this test method are underinvestigation.12. Keywords12.1 circuit resistance; current carrying capacity; membraneswitch;
27、power capacityF 1681 07a2ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infring
28、ement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard
29、or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views
30、known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).F 1681 07a3
