Chapter 2 Getting started
Page 2.12
2.7 Example 4: 7951 with a mA-type pressure transmitter
About this example
This example shows you how to connect a mA-type pressure transmitter to the 7951, and then use the
“Pressure” wizard to configure the system.
In this example, the “Pressure” wizard is used to configure a connection as follows:
x A single pressure transmitter is connected to Analogue Input 3.
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 transmitter to the 7951, as in Figure 2.12.
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.
Set DIP switch 3. Ensure that the DIP-switch, inside the 7951, is set as shown in Figure 2.12 .
Notes:
1. Specified 7951 pins are for Analogue Input 3.
2. DIP-switch position 3 must be set to 4-20mA.
Loop-powered
4-20mA pressure
transmitter
Signal +
Signal -
-
+Power +
Klippon D-type
PL9/5
PL8/2
PL8/3
PL9/8
SK8/24
SK8/2
SK8/3
SK8/25
7951
Power -
D
C
B
A
4
3
2
1
4-20mA PRT
Figure 2.12: DIP-switch and safe area wiring for a mA-type pressure transmitter