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IEC 60688
Edition 4.0 2021-09
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Electrical measuring transducers for converting AC and DC electrical quantities
to analogue or digital signals
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IEC 60688
Edition 4.0 2021-09
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Electrical measuring transducers for converting AC and DC electrical quantities
to analogue or digital signals
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.220.20 ISBN 978-2-8322-1029-1
– 2 – IEC 60688:2021 RLV © IEC 2021
CONTENTS
FOREWORD . 9
INTRODUCTION . 11
1 Scope . 12
2 Normative references. 13
3 Terms and definitions . 13
3.1 General terms . 14
3.2 Terms describing transducers according to the measurand . 17
3.3 Terms describing transducers according to their output load . 18
3.4 Nominal values . 18
3.5 User adjustment Terms describing transducers with provisions to be
adjusted by users . 19
3.6 Influence quantities and reference conditions . 20
3.7 Errors and variations . 20
3.8 Accuracy, accuracy class, class index . 21
4 Class index, permissible limits of intrinsic error, auxiliary supply and reference
conditions General . 21
4.1 Transducer general architecture . 21
4.2 Classification of transducers (TRD) . 22
5 Requirements for TRD1 . 22
5.1 Safety requirements: clearances and creepage distances . 22
5.2 EMC requirements . 22
5.2.1 Immunity . 22
5.2.2 Emission . 23
5.3 Class index requirements . 23
5.3.1 Class index . 23
5.3.2 Class index for transducer used with sensors . 23
5.3.3 Intrinsic error . 23
5.4 Conditions for the determination of intrinsic error . 23
5.5 Auxiliary supply . 25
5.5.1 General . 25
5.5.2 DC supply . 25
5.5.3 AC supply . 25
5.6 Input values . 26
5.6.1 General . 26
5.6.2 Adjustment ranges . 26
5.6.3 Preferred nominal values . 26
5.7 Analogue output signals . 26
5.7.1 General . 26
5.7.2 Output current . 26
5.7.3 Compliance voltage . 26
5.7.4 Maximum output voltage . 26
5.7.5 Interference risk of output current . 27
5.7.6 Output voltage . 27
5.8 Output transfer function . 27
5.9 Digital output signals . 30
5.10 Ripple (for analogue outputs) . 30
5.11 Response time . 30
5.12 Variation due to over-range of the measurand . 30
5.13 Limiting value of the output signal . 30
5.14 Limiting conditions of operation . 31
5.15 Limits of the measuring range . 31
5.16 Limiting conditions for storage and transport . 31
5.17 Sealing . 31
5.18 Stability . 31
6 Tests for TRD1 . 31
6.1 General . 31
6.1.1 Determination of variations . 31
6.1.2 Environmental conditions . 32
6.1.3 Computations . 32
6.2 Variations due to auxiliary supply voltage . 32
6.2.1 Application . 32
6.2.2 Procedure . 32
6.2.3 Computation . 33
Permissible variations . 33
6.3 Variations due to auxiliary supply frequency . 33
6.3.1 Application . 33
6.3.2 Procedure . 33
6.3.3 Computation . 33
6.3.4 Permissible variations . 34
6.4 Variations due to ambient temperature . 34
6.4.1 Application . 34
6.4.2 Procedure . 34
6.4.3 Computation . 34
6.4.4 Permissible variations . 34
6.5 Variations due to the frequency of the input quantity(ies) . 35
6.5.1 Application . 35
6.5.2 Procedure . 35
6.5.3 Computation . 35
6.5.4 Permissible variations . 35
6.6 Variations due to the input voltage . 35
6.6.1 Application . 35
6.6.2 Procedure . 35
6.6.3 Computation . 36
6.6.4 Permissible variations . 36
6.7 Variations due to the input current . 36
6.7.1 Application . 36
6.7.2 Procedure . 36
6.7.3 Computation . 36
6.7.4 Permissible variations . 36
6.8 Variations due to power factor . 37
6.8.1 Application . 37
6.8.2 Procedure . 37
6.8.3 Computation . 37
6.8.4 Permissible variations . 37
6.9 Variation due to output load . 38
– 4 – IEC 60688:2021 RLV © IEC 2021
6.9.1 Application . 38
6.9.2 Procedure .
...