Chapter 1: Installation
Page 14 HygroPro User’s Manual
1.4.2b Compliance Requirements
The HygroPro installation must comply with EN 60079-14 in Europe
and with the National Electrical Code (ANSI/NFPA 70) or part one of
the Canadian Electrical Code (C22.1), as applicable, in North
America. In other regions, additional local codes may also apply.
1.4.2c Electrical Connections
The HygroPro transmitter is certified intrinsically-safe for use in
zone 0. However, the external power must be provided by one of the
following methods:
• an isolated, intrinsically-safe, 24 VDC power supply mounted in
the safe area
• an isolated zener barrier mounted in the safe area and installed
between a standard 24 VDC power supply and the HygroPro
Refer to Figure 6 on the next page for a typical hazardous (classified)
area HygroPro wiring diagram. This installation uses an MTL706
zener barrier, in accordance with the second option listed above.
If using serial communications with a PC, an isolated RS232-RS485
converter mounted in the safe area between the computer and
HygroPro must be used. The converter is typically powered by its
own standard 24 VDC power supply.
!WARNING!
Do NOT power an RS232-RS485 converter from the
same intrinsically-safe 24 VDC power supply used
to power the HygroPro.
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