Chapter 2 Getting started
Page 2.9
2.6 Example 3: 7951 with a mA-type temperature transmitter
About this example
This example shows you how to connect a mA-type temperature transmitter to the 7951, and then use the
“Temperature” wizard to configure the system.
In this example, the “Temperature” wizard is used to configure connections as follows:
x A single temperature transmitter is connected to Analogue Input 3.
Now work through the example by following the instructions below. If you are not sure where the buttons are,
refer to the diagram at the start of this chapter.
Connect the
meter
1. Wire the temperature transmitter to the 7951, as in Figure 2.10
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 below.
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
temperature
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 2.10: DIP-switch and safe area wiring for a mA-type temperature transmitter