D.C. bridges for measuring resistance

Classification. Class index system. Permissible errors for each class. Conditions for testing. Conditions for use. Methods of testing. Markings. Information to be supplied by the manufacturer.

Gleichstrom-Widerstandsmeßbrücken

Ponts à courant continu pour mesure de résistance

Classification. Systèmes de l'indice de classe. Erreurs admissibles pour chaque classe. Conditions de mesure. Conditions d'utilisation. Méthodes d'essai. Marquage. Documentation d'accompagnement.

Enosmerni mostički za meritve upornosti (IEC 60564:1977 + A1:1981)

General Information

Status
Published
Publication Date
18-Apr-1993
Current Stage
6060 - Document made available
Due Date
19-Apr-1993
Completion Date
19-Apr-1993

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EN 60564:1999
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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Gleichstrom-WiderstandsmeßbrückenPonts à courant continu pour mesure de résistanceD.C. bridges for measuring resistance17.220.20Measurement of electrical and magnetic quantitiesICS:Ta slovenski standard je istoveten z:EN 60564:1993SIST EN 60564:1999en01-julij-1999SIST EN 60564:1999SLOVENSKI

STANDARD
SIST EN 60564:1999
SIST EN 60564:1999
SIST EN 60564:1999
SIST EN 60564:1999
SIST EN 60564:1999

IEC•NORMECEIINTERNATIONALEIECINTERNATIONAL60564STAN DARDPremière éditionFirst edition1977-01Ponts à courant continu pour mesure de résistanceD.C. bridges for measuring resistance© IEC 1977 Droits de reproduction réservés — Copyright - all rights reservedAucune partie de cette publication ne peut être reproduite niNo part of this publication may be reproduced or utilized inutilisée sous quelque forme que ce soit et par aucunany form or by any means, electronic or mechanical,procédé, électronique ou mécanique, y compris la photo-including photocopying and microfilm, without permission incopie et les microfilms, sans l'accord écrit de l'éditeur.writing from the publisher.International Electrotechnical Commission3, rue de Varembé Geneva, SwitzerlandTelefax: +41 22 919 0300e-mail: inmail@iec.chIEC web site http: //www.iec.chCommission Electrotechnique InternationaleInternational Electrotechnical CommissionMcNSayHapoAHaH 3nenrpoTexHH4eCNari HOMHCCHACODE PRIXPRICE CODEPour prix, voir catalogue en vigueurFor price, see current cataloguePSIST EN 60564:1999

— 3 —CONTENTSPageFOREWORD5PREFACE5Clause1.Scope 72.Terms and definitions 73.Classification 154.Stability 155.Permissible limits of intrinsic error156.Conditions for the determination of intrinsic errors177.Permissible variations 198.Additional electrical and mechanical requirements 219.Information, markings and symbols 23SIST EN 60564:1999

— 5 —INTERNATIONAL ELECTROTECHNICAL COMMISSIOND.C. BRIDGES FOR MEASURING RESISTANCEFOREWORDI) The formal decisions or agreements of the IEC on technical matters, prepared by Technical Committees on which all theNational Committees having a special interest therein are represented, express, as nearly as possible, an internationalconsensus of opinion on the subjects dealt with.2)They have the form of recommendations for international use and they are accepted by the National Committees in thatsense.3)In order to promote international unification, the IEC expresses the wish that all National Committees should adoptthe text of the IEC recommendation for their national rules in so far as national conditions will permit. Any divergencebetween the I EC recommendation and the corresponding national rules should, as far as possible, be clearly indicatedin the latter.PREFACEThis standard has been prepared by Sub-Committee 13B, Electrical Measuring Equipment, ofIEC Technical Committee No. 13, Electrical Measurements.Drafts were discussed at the meetings held in Toronto in 1972 and in Bucharest in 1974. As a resultof this latter meeting, the draft, Document 13B(Central Office)49, was submitted to the NationalCommittees for approval under the Six Months' Rule in July 1975.The following countries voted explicitly in favour of publication:ArgentinaPolandAustriaRomaniaBelgiumSouth Africa (Republic of)DenmarkSwedenFranceSwitzerlandGermanyTurkeyHungaryUnited KingdomIsraelUnited States of AmericaItalyYugoslaviaJapanOther IEC publications quoted in this standard:Publication Nos. 27:Letter Symbols to be Used in Electrical Technology.51:Recommendations for Direct Acting Indicating Electrical Measuring Instruments and theirAccessories.160:Standard Atmospheric Conditions for Test Purposes.414:Safety Requirements for Indicating and Recording Electrical Measuring Instruments and theirAccessories.SIST EN 60564:1999

— 7 —D.C. BRIDGES FOR MEASURING RESISTANCE1.ScopeThis standard applies to d.c. bridges for measuring resistance. It also applies to auxiliaryequipment which is a built-in part of the bridge.This standard does not apply to bridge comparators*, nor to self-balancing bridges nor to thosewhich employ graduations on the null detector to obtain a part of the indicated value, nor toexternal auxiliary equipment used with the bridge.2.Terms and definitionsFor the purposes of this standard, the following definitions apply:2.1 D.C. bridge for measuring resistance (hereinafter designated "bridge")The assembly of at least three resistance arms which, together with a test resistor, forms a bridgenetwork; a source of direct current and a null detector are also required for its operation: thesemay or may not be built-in. At balance, there exists a calculable relationship between the resistancevalues of the resistors.Note. — A d.c. bridge for measuring resistance may be intended to measure two-terminal or four-terminal resistors eachwith or without a leakage current screen (circuit): it will be termed accordingly a two-terminal bridge or a four-terminal bridge with or without provision for a leakage current screen (circuit).2.2 Test resistorThe resistor whose resistance value is to be measured.2.3 Two-terminal resistorA resistor having a single combined current-potential terminal at each end.2.4 Four-terminal resistorA resistor having two terminals at each end. one for connection into a current-carrying circuitand one for connection to a potential measuring circuit.Note. — The value of the resistance is defined as the quotient of the potential difference between the two potential terminalsto the current entering and leaving the current terminals, provided that no current is drawn from the potentialterminals.* A bridge comparator is a device intended to compare two resistors, e.g. a two-arm adjustable ratio set.SIST EN 60564:1999

— 9 —2.5 Resistor with leakage current screen (circuit)A resistor having a leakage current screen (circuit) connected to a separate terminal, which is oftencalled the "guard terminal".Note. — A resistor with leakage current screen (circuit) may be represented as a delta network consisting of an equiv-alent value of resistance connected between each pair of terminals. Of these three resistances, the resistance betweenthe two main terminals is the main equivalent resistance which is intended to be measured. The other two resistancesof the delta network are usually insulation (leakage) resistances which, for very high values of the main equiv-alent resistance, may be of the same order or smaller than it. The main equivalent resistance may appeareither as a two-terminal resistor or as a four-terminal resistor.2.6 Resistance decadeA multiple resistor which, usually by means of a switching device, allows the selection of acombination of resistance values rising in equal steps, each step corresponding to an incrementof a decadic resistance value such as, for example, 0.1 S2, 1 S2 or 10 O.Note. — A resistance decade generally allows a selection of 10, 1 I or 12 resistance values (including zero).2.7 Range-changing deviceA switch or similar device whereby the effective range may be multiplied by a factor (e.g. 0.1)which is known as the "range factor" or "range multiplier".2.8 Measuring dialsThe dials from which, taking into account the setting of the range-changing device(s), if any,the value of the test resistor is determined.2.9 Connecting resistance (potential)For a four-terminal bridge, the resistance of the conductor connecting a potential terminalof the bridge to the corresponding potential terminal of the test resistor, plus the resistance ofthe potential conductor inside the test resistor.2.10 Link resistance (current)For a four-terminal bridge, the resistance of the conductor connecting a current terminal ofthe bridge to the corresponding current terminal of the test resistor, plus the resistance of the currentconductor inside the test resistor.2.11 Auxiliary equipmentAdditional equipment, which is or is not an integral part of the bridge, necessary to enable thebridge to operate accurately and safely as specified.2.12 Ripple contentThe ripple content of a d.c. supply, expressed as a percentage of the mean value of the supply is:r.m.s. value of the fluctuating component X 100mean value of the supplySIST EN 60564:1999

11 —2.13 Leakage current screen (circuit)A conducting path which prevents leakage currents from affecting the results of measurements.Note. — The terminal of the leakage current screen (circuit) is often called the "guard terminal".2.14 Electrostatic screenAn electrically conductive enclosure or coating intended to protect the enclosed space fromexternal electrostatic influences.2.15 Measuring terminalsThe terminals to which the test resistor is intended to be connected.2.16 Measuring circuitThe internal circuit of the bridge which is (or can be) conductively connected to the measuringterminals.2.17 Effective rangeFor a specified range factor, the range between the minimum and maximum values of resistancewhich can be measured with the stated accuracy.2.18 Overall effective rangeUsing all range factors, the overall range of resistance values which can be measured with thestated accuracy.2.19 Dial settingThe setting of the measuring dial(s) after balancing the bridge, multiplied by the range factor,if applicable, when determining the value of a test resistor.2.20 ResolutionFor measuring dials with discrete settings only, the resistance corresponding to one step on themeasuring dial of lowest value on any specified range.For measuring dials in which one dial is continuously adjustable, the resistance corresponding tothe smallest division on the measuring dial of lowest value in any region of the dial setting on anyspecified range.Note. — For continuously adjustable dials which are non-linear, the resolution may change with the dial setting.2.21 Influence quantityA quantity, other than the measured quantity, which is liable to cause unwanted variation inthe dial setting.2.22 Reference conditionsThe specified conditions under which the bridge meets the requirements concerning intrinsicerror(s).SIST EN 60564:1999

132.23 Reference valueA specified single value of an influence quantity at which, within the stated tolerance, the bridgemeets the requirements concerning intrinsic error(s).2.24 Reference rangeA specified range of values of an influence quantity within which the bridge meets the requirementsconcerning intrinsic error(s).2.25 Variation with influence quantityThe difference between the dial settings for a constant value test resistor when an influencequantity assumes successively two different specified values.2.26 Nominal range of useA specified range of values which each influence quantity can assume without causing a variationexceeding the specified limits.2.27 Limiting values of an influence quantityExtreme values which an influence quantity may assume without the bridge being damaged orpermanently altered in such a way that it no longer satisfies the requirements of its accuracy class.2.28 Fiducial valueA single value for each effective range to which reference is made in order to specify the accuracyof a bridge.Unless otherwise stated by the manufacturer, the fiducial value of a given effective range is thehighest integral power of 10 within that range.2.29 ErrorThe value obtained by subtracting the true value of the measured quantity from the dial setting.Notes /.—Since the true value cannot be determined by measurement. a value obtained under specified test conditionsand at a specified time is used. This value is derived from national measurement standards or a measurementstandard agreed upon by the manufacturer and the user.2.—The error due to any auxiliary equipment which is not built-in to the bridge is not included in the error of thebridge.2.30 Intrinsic errorAn error determined under reference conditions.2.31 AccuracyThe accuracy of a bridge is defined by the limits of intrinsic error and the limits of variationsdue to influence quantities.2.32 Accuracy classA class of bridges, the accuracy of all of which can be designated by the same number ifthey comply with all the requirements of this standard.2.33 Class indexThe number which designates the accuracy class.SIST EN 60564:1999

— 15 —3. ClassificationBridges specified in this standard are classified:3.1 According to whether they measure the values of two-terminal or four-terminal resistors with orwithout a leakage current screen (circuit).Note. — Some bridges may be capable of measuring the value of more than one type of resistor.3.2 According to their accuracy classes, as defined in Sub-clause 2.32, as follows :a)0.0010.0020.0050.010.020.050.1b)10 ppm20 ppm50 ppm100 ppm200 ppm500 ppm1000 ppma)0.20.512510b)2000 ppm5000 ppm10000 ppm20000 ppm50000 ppm100000 ppmThe class index of a bridge may be expressed either in percent using a) or parts per million(ppm) using b), or both.If a bridge has several measuring ranges, each range may have its own class index.Note. — Accuracy classes 2 ... 10 (20000 ppm ... 100000 ppm) arc not intended for use except with bridges measuringvery high values of resistance.4.StabilityBridges shall comply with the relevant limits of intrinsic error specified for their respectiveaccuracy classes for the duration of one year from the date of certification associated withdelivery or another date to be agreed upon by the manufacturer (or responsible supplier) and theuser (or purchaser), provided that the conditions of use, transport and storage specified bythe manufacturer are complied with.Note.For bridges, stability with regard to time is an essential characteristic. Here, it is specified only for the durationof one year, but experience has shown that the rate of change due to ageing effects generally decreases with time.5.Permissible limits of intrinsic errorThe permissible limits of error of a bridge are composed of two parts: constant term related to the fiducial value; variable term proportional to the dial setting.SIST EN 60564:1999

— 17 —5.1 The two limits ar
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