IEC 60584-3:2021 pdf download

IEC 60584-3:2021 pdf download.Thermocouples – Part 3: Extension and compensating cables – Tolerances and identification system
1 Scope
It 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 of electric cables. IEC 60584-3 standardizes these cables. It specifies identification and manu- facturing tolerances for extension and compensating cables (mineral insulated extension and compensating 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 industrial process 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.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply. ISO and IEC maintain terminological databases for use in standardization at the following ad- dresses: IEC Electropedia: available at http://www.electropedia.org/ ISO Online browsing platform: available at http://www.iso.org/obp 3.1 extension cables cables manufactured from conductors having the same nominal composition as those of the corresponding thermocouple Note 1 to entry: The cables are designated by the letter “X” following the designation of the thermocouple, for example “JX”. 3.2 compensating cables cables manufactured from conductors having a composition different from the corresponding thermocouple Note 1 to entry: The cables are designated by the letter “C” following the designation of the thermocouple, for example “KC”. In some cases, different tolerances apply for the same thermocouple type over different temperature ranges. 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 or compensating cable into the measuring circuit
4 General
Both extension and compensating cables are used for the electrical connection between the open 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.
5 Tolerance values
Table 1 shows the specified tolerance for extension and compensating cables when used at temperatures within the ranges indicated as “temperature range of validity”. Temperature range of validity can be restricted to figures lower than those shown in the table because of temperature limitations imposed by the insulant.A cable comprising two copper conductors may be used with Type B thermocouples. The ex- pected maximum additional deviation within the cable temperature range 0 °C to +100 °C is 40 μV. The equivalent in temperature is 3,5 °C when the measuring junction of the thermo- couple is at 1 400 °C.
6 Colour coding
6.1 Negative conductor The insulation of the negative conductor shall be coloured in WHITE for all thermocouple types. 6.2 Positive conductor The insulation of the positive conductor shall be coloured correspondingly to the thermocou- ple as indicated in Table 2. 6.3 Outer sheath The outer sheath, if any, shall be coloured as indicated in Table 2. The outer sheath, if any, shall be colored as given in Table 2. In the case of possible confusion with existing IEC color code specification of cables, the color shall be indicated by other means, for instance by put- ting a label, tag or sticker of the specified color in the Table 2.