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1、BRITISH STANDARD BS 3467:1962 Method of test for Temperature coefficient of resistance of alloy wire for precision resistors Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 29 05:32:16 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 3467:1962 This British Standard, having been approved by the Elec
2、trical Industry Standards Committee and endorsed by the Chairman of the Engineering Divisional Council, was published under the authority of the General Council on 19 January 1962 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference ELE/76 Draft for comme
3、nt AA(ELE) 3621 ISBN 0 580 03880 7 Co-operating organizations The Electrical Industry Standards Committee under whose supervision this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: The Government depa
4、rtments and scientific and industrial organizations marked with an asterisk in the above list, together with the following, were directly represented on the Committee entrusted with the preparation of this standard: AdmiraltyElectricity Council, Generating Board and the Air MinistryArea Boards in En
5、gland and Wales* Associated Offices Technical CommitteeElectronic Engineering Association Association of Consulting EngineersEngineering Equipment Users Association (Incorporated)*Independent Cable Makers Association* Association of Supervising Electrical EngineersInstitution of Electrical Engineers
6、 British Electrical and Allied IndustriesMinistry of Aviation Research AssociationMinistry of Labour (Factory Inspectorate) British Electrical and Allied ManufacturersMinistry of Power Association*Ministry of Works British Electrical Development AssociationMunicipal Passenger Transport Association B
7、ritish Railways, The British Transport(Incorporated) CommissionNational Inspection Council for Electrical Cable Makers Association*Installation Contracting Crown Agents for Oversea Governments andNational Physical Laboratory (D.S.I.R.)* AdministrationsOil Companies Materials Association Electric Lam
8、p Industry CouncilPost Office* Electric Light Fittings AssociationPublic Transport Association (Incorporated) Electrical Contractors AssociationSouth of Scotland Electricity Board (Incorporated)War Office Electrical Contractors Association of Scotland Aluminium Development AssociationEngineering Ind
9、ustries Association Aluminium Industry CouncilHigh Conductivity Copper Association Association of Plastic Cable MakersRadio and Electronic Component Copper Development AssociationManufacturers Federation Covered Conductors AssociationManufacturers of resistance wire Amendments issued since publicati
10、on Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 29 05:32:16 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 3467:1962 BSI 12-1999i Contents Page Co-operating organizationsInside front cover Forewordii 1Scope1 2Temperature coefficient of resistance1 3Test specimen1 4Terminal
11、s1 5Preliminary treatment1 6Apparatus2 7Baths2 8Temperature measurements2 9Resistance measurements2 10Procedure3 11Resistance-temperature equation4 12Calculation of constants4 Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 29 05:32:16 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 3467:1962 ii B
12、SI 12-1999 Foreword This standard makes reference to the following British Standard: BS 3239, Determination of resistivity of metallic electrical conductor materials. This British Standard has been prepared mainly to meet the need for a standard method of test for the relation of resistance to tempe
13、rature of alloy wire used in the manufacture of precision resistors for electronic equipment. It is, however, equally applicable to material used in resistance standards. Acknowledgment is made to the American Society for Testing Materials on whose Standard Method of Test B84-52 this British Standar
14、d is largely based. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This
15、 document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 5 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun s
16、heffieldun, na, Wed Nov 29 05:32:16 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 3467:1962 BSI 12-19991 1 Scope This British Standard describes a procedure for determining the change of resistance with temperature of alloy wire (including material of non-circular section) used for resistance standa
17、rds and precision resistors for electrical apparatus. The maximum range of temperature covered is 65 C to + 200 C. Provision is made for presenting the results in the form of a graph, as a change of resistance between specified temperatures, or as the coefficients in a resistance-temperature equatio
18、n. 2 Temperature coefficient of resistance Except where otherwise stated, in this British Standard, “Temperature coefficient of resistance” is the constant-mass temperature coefficient, i.e. that of a conductor with terminals fixed to it, but left free to expand or contract. This is the most commonl
19、y used constant in this field. For its relation to other constants, such as the temperature coefficient of volume resistivity, the reader is referred to Appendix C of BS 32391). 3 Test specimen a) The test specimen shall be of a length that will give a resistance that can be measured to the required
20、 accuracy. b) Care shall be taken that the strains introduced in the preparation of the specimen are as small as possible. c) If the wire is insulated, it may be wound in a circular coil, with or without a former, not less than 5 cm in diameter. d) If the wire is not insulated, it may be wound on an
21、 insulating former in a manner that will not introduce strains in the wire when subjected to temperature changes. e) The tension used in winding shall be no more than sufficient to produce a neat coil of insulated wire or to prevent the touching of adjacent turns when bare wire is wound on an insula
22、ting former. f) For fine wires of sufficiently high resistivity, straight wire specimens may be used. 4 Terminals a) If the resistance of the specimen is less than 100 ohms, it is preferable and may be essential to use both current and potential leads in measuring the resistance. A wire shall then b
23、e brazed, soldered or welded close to each end of the specimen for use as a potential lead. The heating involved in this operation may modify the properties of the alloy over a short distance. To reduce the effect on the measured values to a negligible amount, the specimen should be not less than 50
24、 cm in length. b) If the two-terminal method of resistance measurement is used, the terminals may be clamps or, alternatively, a copper wire may be brazed or soldered to each end of the specimen for use as a terminal. In either case, the resistance of the terminal connections shall be less than 0.02
25、 per cent of that of the specimen. c) In coils made of fine wire where there is not sufficient rigidity in the coil itself to furnish a satisfactory support for the terminals, short lengths of thin glass or ceramic rod may be bound across the coil to act as struts and furnish an anchorage for the te
26、rminals. 5 Preliminary treatment The prepared specimen shall be subjected to a temperature of 140 5 C for not less than 16 hours for alloys of the 80/20 nickel/chromium type and of the copper/manganese type with an approximate composition 84/12, and to a baking period specified by the manufacturer f
27、or other alloys. The purpose of this treatment is to stabilize the resistance of the wire, and the measured characteristics of the specimen after treatment shall be considered as the true temperature resistance characteristics of the wire. 1) BS 3239, “Determination of resistivity of metallic electr
28、ical conductor materials”. Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 29 05:32:16 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 3467:1962 2 BSI 12-1999 6 Apparatus The apparatus for making the test shall consist of one or more baths for maintaining the specimen at the desired temperatures,
29、thermometers for measuring the temperatures of the baths, and suitable means for measuring the resistance of the specimen. 7 Baths a) Baths for use with alloys with temperature coefficients of 20 p.p.m. per degC and less shall consist of Chemically neutral oil. The oil shall be of such quantity and
30、so well stirred that the temperature in the region occupied by the specimen and the thermometer will be uniform within 0.1 degC for any temperature between 0 C and 40 C, and 0.2 degC for any temperature between 40 C and 80 C. In an automatically controlled bath, the temperature of the bath at any ti
31、me during the test at any temperature level shall not differ from its mean temperature by more than 0.2 degC. In a manually controlled bath, when at a nominally constant temperature, the rate of change of temperature at any temperature level shall not exceed 0.2 degC per minute. b) Baths for use wit
32、h other alloys, and all alloys outside the temperature range from 0 C to 80 C, shall be as follows: i) Baths for use below 15 C shall consist of chemically neutral toluene, trichlorethylene or equivalent material. ii) Baths for use above 15 C shall consist of chemically neutral oil with a low viscos
33、ity and a flash point at least 50 degC higher than the temperature of use. The liquid in these baths shall be of such quantity and so well stirred that the temperature in the region occupied by the specimen and the thermometer will be uniform within 0.5 degC for any temperature up to and including 1
34、00 C, and 1.0 degC for any temperature above 100 C. If the temperature range is less than 100 degC, the uniformity of temperature shall be correspondingly closer. The sample shall be rinsed free of oil by immersion in an acetone bath at room temperature before being placed in a toluene bath. 8 Tempe
35、rature measurements In tests on alloys with temperature coefficients of 20 p.p.m. per degC and less, the temperature shall be measured either with a laboratory type mercurial thermometer or a resistance thermometer. The thermometer shall have sufficient sensitivity to indicate temperature changes of
36、 0.1 degC. It is sufficiently accurate to measure temperature differences to 0.2 degC in the range up to and including 40 C, and to 0.3 degC in the range from 40 C to 80 C. For other alloys, and for all alloys outside the range from 0 to 80 C, the temperature shall be measured to an accuracy of 0.5
37、degC or 1 per cent of the temperature range, whichever is the smaller. 9 Resistance measurements a) The changes of resistance of the specimen shall be measured by apparatus capable of determining such changes to 0.001 per cent of the resistance of the specimen. b) The connections between the specime
38、n and the measuring device shall be such that changes in the resistance of these connections due to changes in their temperature do not appreciably affect the measurement of the change in resistance of the specimen. c) The temperature of the measuring apparatus shall not change during the test by an
39、 amount sufficient to introduce appreciable errors in the results. d) The test current shall not be of such a magnitude as to produce an appreciable change in resistance of the specimen or measuring apparatus due to the heating effect. To determine experimentally that the test current is not too lar
40、ge, the specimen may be immersed in a bath having a temperature at which the wire has been found to have a relatively large change in resistance with temperature. The test current is applied and maintained until the resistance of the specimen has become constant. The current is then increased by 40
41、per cent and maintained at this value until the resistance has again become constant. If the change in resistance is greater than 0.001 per cent, the test current is too large and should be reduced until the foregoing limitation is reached. Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 29 05:3
42、2:16 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 3467:1962 BSI 12-19993 e) The measurements shall be made in such a way that the effects of thermo-electromotive forces and parasitic currents are minimized. Thus, in a bridge circuit, if there is appreciable thermo-electromotive force it may be desi
43、rable to close the galvanometer key first. If the galvanometer deflects, it is allowed to reach a steady deflection, and balance is regarded as having been achieved if there is no further movement of the galvanometer when the battery key is closed. If, however, there is appreciable inductance in the
44、 circuit there may be a transient deflection when the battery key is closed, and it is then sometimes better to close the battery key first. The bridge is adjusted until there is no deflection when the galvanometer key is closed, but since the balance may be affected by thermo-electric effects, it i
45、s necessary to take another reading with the battery connections reversed. The resistance of the specimen is taken as the mean of the two readings. If a potentiometer method is used, the specimen under test and a high quality resistance standard are connected in series to a steady and adjustable sou
46、rce of direct current, and the potentiometer is switched alternately to the standard and the specimen. It is unnecessary to standardize the potentiometer against a standard cell; the potentiometer current and/or the current through the specimen can be adjusted so that when connected to the standard
47、the potentiometer balances at some convenient round reading S (such as 1.00000). The potentiometer is then quickly switched to the specimen and the reading R is taken at balance. The resistance of the specimen is given by In order to eliminate the effect of thermal e.m.f., it is desirable to repeat
48、the procedure with both potentiometer current and specimen current reversed. The resistance of the specimen is taken as the mean of the two results. f) Whatever the instrument used to measure resistance, ranges shall never be changed between observations. Resistance changes should be measured by adj
49、usting the dials of lowest denomination only and, by suitable choice of initial setting, making use of the “10” position when necessary, the number of dials requiring to be altered during a series of tests should be reduced to the fewest possible. 10 Procedure a) The test specimen shall be connected in the measuring circuit and shall be entirely submerged in the bath. For a check on the reproducibility of the measurements, an initial resistance measurement shall be made at room temperature. The temperature of the bath shall be raised or the specimen tr
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