9
Where:
D = Max. cable length in feet.
V
S
= Power supply voltage.
R = Cable resistance in ohms per 1000 feet.
Example:
VS = 24 Volts
R = 16.1 (22 AWG cable)
=
(24 10)
(
4 10
)(
16.1
)
= 21,739
d. Wiring for a Hazardous Area Installation
CAUTION: This section provides general guidelines for hazardous area wiring. However, regardless of
anything stated here, the MS2601E must be installed in full compliance with the control drawing
located on page 18 and all of the local area requirements.
ATTENTION: Cette section fournit des directives générales pour le câblage en zone dangereuse.
Cependant, indépendamment de tout ce qui est indiqué ici, le MS2601E doit être installé
conformément au schéma de contrôle situé à la page 18 et à toutes les exigences locales.
Whenever an electrically driven sensor or measuring device is used in a potentially explosive
environment the measuring system must be installed in such a way that electrical energy is either
effectively isolated from the explosive environment (via explosive-proof containers, cable conduits,
etc.) or the amount of electrical energy produced in the hazardous area must be limited to an
permitted level.
Limiting electrical energy is the most practical method of protecting the MS2601E measuring system
when the Transmitter is installed in a hazardous area. In the MS2601E system, electrical energy limits
are maintained using a power supply with Um of 28V installed in the 4-20 mA current loop per
standard practice. The voltage shall be maintained all the time in accordance with the guidance given
in IEC 60079-14.
Caution: In general Safety barriers are not necessary but when a safety barrier is used with the
MS2601E system, the current loop cable must be connected to the barrier’s hazardous area terminals
and the barrier output voltage should not exceed 28V at any circumstances. All other connections
must be made to the barrier’s safe area terminals.
The type of repeater safety barrier employed in the MS2601E system depends on the specific
classification of the hazardous environment in question. Metal Samples will provide, upon request,
assistance and technical advice in the selection of a repeater safety barrier or its equivalent.
The maximum length of the current loop cable that connects the MS2601E Transmitter to the
repeater safety barrier is as follows:
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