IEC 60584-3 pdf – Thermocouples – Part 3: Extension and compensating cables – Tolerances and identification system

IEC 60584-3 pdf – Thermocouples – Part 3: Extension and compensating cables – Tolerances and identification system
lt is necessary for thermocouple temperature measurement that the electro-motive force (ab-breviated as e.m.f. hereafter) of the thermocouple circuit is precisely measured by a measur-ing instrument. A thermocouple is electrically connected to the instrument by a proper pair ofelectric cables. IEC 60584-3 standardizes these cables. lt specifies identification and ‘manu-facturing tolerances for extension and compensating cables (mineral insulated extension andcompensating cables are not included) provided directly to users of industrial processes.These tolerances are determined with respect to the e.m.f. versus temperature relationship of
IEC 60584-1. The requirements for extension and compensating cables for use in industrialprocess control are specified.
Extension and compensating cables may consist of a single strand (solid) wire or multi-stranded wire for which this document is applied.Specification for extension and compensat-ing conductors of forms of rods, flat wires or strips can be established by agreement between
suppliers and users.
2Normative references
The following documents are referred to in the text in such a way that some or all of their con-
tent constitutes requirements of this document. For dated references, only the edition citedapplies. For undated references, the latest edition of the referenced document (including anyamendments) applies.
IEC 60584-1，Thermocouples – Part 1: EMF specifications and tolerances
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and lEC maintain terminological databases for use in standardization at the following ad-dresses:
·IEC Electropedia: available at http://www.electropedia.orgl
.Iso Online browsing platform: available at http://www.iso.orglobp
3.1
extension cables
cables manufactured from conductors having the same nominal composition as those of thecorresponding thermocouple
Note 1 to entry: The cables are designated by the letter “X”following the designation of the thermocouple,forexample “JX”.
3.2
compensating cables
cables manufactured from conductors having a composition different from the correspondingthermocouple
Note 1 to entry: The cables are designated by the letter “C”following the designation of the thermocouple,forexample “Kc”. In some cases,different tolerances apply for the same thermocouple type over diferent temperatureranges.These are distinguished by additional letters such as,for example，RCA and RCB.
3.3
tolerance
maximum allowable deviation in microvolts caused by the introduction of the extension orcompensating cable into the measuring circuit
4 General
Both extension and compensating cables are used for the electrical connection between theopen ends of a thermocouple and the reference junction in those installations where the con-
ductors of the thermocouple are not directly connected to the reference junction. A cable al-ways consists of a specific pair (negative and positive conductor), to be connected to the cor-
responding thermocouple. The thermoelectric properties of extension and compensating ca-bles shall be close to the properties of the corresponding thermocouple. Products are manu-factured for each thermocouple type,using various alloy formulations for various purposes.The key characteristic is that the pair of conductors meets the specified e.m.f. tolerance re-quirements.
5Tolerance values
Table 1 shows the specified tolerance for extension and compensating cables when used attemperatures within the ranges indicated as “temperature range of validity”. Temperaturerange of validity can be restricted to figures lower than those shown in the table because oftemperature limitations imposed by the insulant.