4.3 Wiring ST 3000 Transmitter, Continued
Approval body
requirements
If your transmitter was ordered with Table III option 3N for self-
declared approval per 94/9/EC (ATEX4), you must use a power supply
that includes a voltage limiting device that will keep the voltage to the
transmitter from exceeding 42 Vdc. You can achieve this by using a
battery as the supply or one of these voltage limiting means.
• Double wound mains transformer per BS 3535 or equivalent.
• An adequately rated zener diode whose voltage is not significantly
higher than the rated voltage.
• An adequately rated semiconductor voltage regulator.
Lightning protection
When your transmitter is equipped with optional lightning protection,
you must connect a wire from the transmitter to ground as shown in
Figure 15 to make the protection effective. We recommend that you use
a size 8 (American Wire Gage) or (8.37mm
2
) bare or green covered
wire.
Figure 15 Ground Connection for Lightning Protection.
Electronics
Housing
Connect to
Earth Ground
Continued on next page
42 ST 3000 Release 300 Installation Guide 2/05
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