BS 5754:1987 pdf free.SPECIFICATION FOR ELECTRICAL ANALOGUE AND STATE SIGNALS FOR USE IN COAL MINES.
BS 5754 specifies requirements for apparatus incorporating signal circuits intended to be certified intrinsically safe for use in coal mines and which have inputs or outputs, as appropriate, in the form of d.c. voltage analogue signals (type V), or state signals (type S).
It specifies those electrical input and output characteristics of signal sources and signal loads necessary to achieve operational compatibility and also to simplify design for compliance with the relevant standards for intrinsic safety.
Section 1 specifies the general requirements applicable to both types of signals. Sections 2 and 3 contain specific requirements for voltage analogue and state signals respectively.
NOTE The titles of the publications referred to in this standard are listed on the inside back cover.
4 Power supplies
4.1 All apparatus requiring an external power supply shall be capable of working from either a power supply specified in BS 6182, or a non-intrinsically safe mains power supply having a voltage within the limits of + 10 % and — 25 % of the nominal value.
In the latter case, apparatus for use in a hazardous area shall be either housed in a flameproof enclosure, or afforded an alternative type of protection as specified in BS 5501.
NOTE The value of the mains voltage is not specified as a requirement of this standard. The preferred values are 120 V and/or 240 V, or 550 V andlor 1100 V r.m.s. 50 Hz frequency.
4.2 Reversal of power supply polarity shall not damage the apparatus.
5 Interconnection via multicore cab1es:
Analogue and state signals shall only be routed through multicore cables containing other circuits complying with this standard provided that either:
a) it is permitted by the certification documents; or
b) connection is made by way of a safety coupler unit acceptable to a certifying authority for this usage.
NOTE Examples of safety couplers that have been used for this purpose are shown in Appendix A.BS 5754:1987 pdf download.