1、Designation: F 1681 07Standard 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 o
2、f 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 p
3、art 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, anddoe
4、s 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 1680 Test Method for Determining Circuit Resistance of aMembrane Switch3. Terminology3.1 Definitions:3.1.1 conductor resistancethe measured electrical resis-tance thr
6、ough 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 that a circuit can conduct without sustain-ing damage.3.1.4 membr
7、ane 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 points in acircuit loop, possibly including a switch.4. Significa
8、nce 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 thoroughunderstanding of CCC allows manufacturers to take it into
9、account 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).4.3 Since a number of design parameters, such as tracewidth, ink
10、 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 been tested should be considered unreliable forfuture use.1This t
11、est method is under the jurisdiction of ASTM Committee F01 onElectronics and is the direct responsibility of Subcommittee F01.18 on MembraneSwitches.Current edition approved July 1, 2007. Published August 2007. Originallyapproved in 1996. Last previous edition approved in 2002 as F 168196(2002).2For
12、 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 International, 100 Barr Harbor Drive, PO Box C700
13、, West Conshohocken, PA 19428-2959, United States.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 monitor
14、the progress of the test.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 Relative humidity, and5.1.3 Barometric pressure.6. Hazard6.1 The u
15、ser 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 highest rating.7. Apparatus7.1 Controlled current and voltage source
16、, 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 of the circuitunder test.7.3 Suitable Device, to apply a consis
17、tent, repeatable forcewith an elastomeric probe in accordance with Test MethodF 1680 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 mechanical device instead of a human fingerto close the switc
18、h.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 the testspecimen to the power supply.8.2.1.1 If the specimen
19、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 thermocouple isused record the temperature at the end of each leve
20、l. Recordany visual observations of degradation. Record the resistancevalue of the specimen (with the power supply off) or bycalculation (using a volt meter across the specimen).8.2.3 Adjust the power supply to the next current level,dwell for 1 min and record the current, voltage (and tempera-ture)
21、 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 current) level, achange in the voltage range is permissible.8.2.5 At the conclusion of t
22、esting 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 specifications of all apparatus,10.1.2 Date of test,10.1.3 Person performing test
23、,10.1.4 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 description of partunder test,10.1.10 Description of test points and connection,10.1.11 Descri
24、ption 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 visual or resistance changesobserved, and10.1.12.3 The user interface temperature (thermocoup
25、le), 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 the specified amount (at the desired voltage andcurrent level) or without exceeding a tem
26、perature 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; power capacityF 1681 072ASTM International takes no position respecting the validity of an
27、y 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 infringement of such rights, are entirely their own responsibility.This standard is subject to rev
28、ision 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 or for additional standardsand should be addressed to ASTM International Headquarters. Your
29、 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 known to the ASTM Committee on Standards, at the address shown below.This standard is copyr
30、ighted 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 073
