Chapter 2 Getting started
Page 2.2
2.4 Example 1: 7951 with a 7810/11/12 gas density meter
About this example
This NON-HAZARDOUS (SAFE) AREA ONLY INSTALLATION† example shows you how to connect either a 7810,
7811 or 7812 gas density meter to the 7951, and then uses the “Density 1” wizard to configure the system.
In this example, the “Density 1” wizard is used to configure a connection as follows:
x A single densitometer is connected to Density Input 1.
Work through the example by following the instructions below. If you are not sure where the buttons are, refer to
Chapter 6.
Connect the
meter
1. Wire the meter to the 7951, as in:
Figure 2.1 for a 7810 or a 7811 gas density meter OR
Figure 2.2 for a 7812 gas density meter.
Note: Refer to meter documentation for other wiring arrangements.
2. Earth the 7951 to a suitable earth point.
EMC Notes:
To meet the EC Directive for EMC (Electromagnetic Compatibility), it is recommended that
the Flow Computer be connected to transducers using a suitable instrumentation cable
containing individually shielded twisted pairs and an overall screen to cover all cores.
The instrumentation cables should have individual screen(s), foil or braid over each
twisted pair and an overall screen to cover all cores. Where permissible, and depending
on the earthing scheme employed at the installation, the overall screen should be
connected to the earthed metal work at both ends (360° bonding where possible). This
may have multiple protective earth connections to the pipe work or the building structure
and not connected to the individual screen(s) or Instrumentation or Zener barrier grounds.
The individual inner screen(s) should be connected at one end only, normally the
controller (e.g. Flow Computer) end. These should be connected to the Instrumentation or
Zener barrier ground.
Use suitable cables that meet BS5308 multi-pair Instrumentation Types 1 or 2.
Klippon D-type
PL5/9
PL5/1
PL5/10
PL5/2
SK6/22
SK6/14
SK6/24
SK6/15
7951
7810/11
POS
NEG
SIG
Figure 2.1: Safe area wiring for a 7810/11 (3-wire arrangement)
†Hazardous area considerations: Refer to meter documentation for details of Intrinsically Safe Barrier/Isolator requirements.