Honeywell FlexLine SmartServo 954 - Enraf Fieldbus (HCI-BPM); The HCI-BPM Board with Its Isolation Transformer

COMMISSIONING
58 Service Manual Part No.: 4417340 Revision 1
954 SmartServo FlexLine
Enraf Fieldbus (HCI-BPM)
7.3.3.1 Introduction
The Host Communication Instrument - Bi-Phase Mark (HCI-BPM) board
is a communication module for the instrument (gauge).
Figure 7-5 The HCI-BPM board with its isolation transformer
As a result of any requirements on the cable quality, the connection of
10 to 15 devices per field bus, and cable lengths up to 10 km, the Bi-
Phase Mark (BPM) signalling is used in many data transmission
installations between various instrumentation and Communication
Interface Unit (CIU) configurations.
Also, the BPM technology provides excellent protection against
lightning. For the exchange of the BPM signals, the HCI-BPM board
uses an isolation transformer for galvanic isolation (see Figure 7-5).
Further protection against heavy lightning is realized by internal ground
shields, separated wiring, and ground tracks.