Instruction manual

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INM4840-5 Nov 2007
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5.3.2 MTL4842 – setting and configuration
Up to 16 MTL4842 HART interface modules can be connected to a
single MTL4841 communications module. Each MTL4842 must be
configured with a unique address by using the four switches located
on the top of the module. Table 5.2 shows the switch settings for the
individual addresses.
5.3.3 Operation at power-up
The MTL4840 system is controlled by a host computer running
instrument management software. Although the software is needed
to operate the system, some checks can be made on the correct
functioning of the hardware in isolation. These checks are made
by observing the operation of the LEDs on top of the MTL4841 and
MTL4842.
Self-test checks
When power is applied to the MTL4841 and MTL4842, the following
events should happen:
The green PWR LED on these modules will light.
The red ACTIVE LED on the MTL4842 will light to show that it is
being addressed by the MTL4841.
LEDs A to D light in sequence as shown in table 5.3, as the
MTL4842 scans once around all the loop addresses 1 to 16.
The sequence is repeated with each MTL4842.
Table 5.3
● = off ❍ = on
Note: Address 16 is shown by all four LEDs being
extinguished.
Following this, the MTL4841 enters either the scanning mode or the
scanning disabled mode.
The 'standard' MTL4841 module is delivered in MTL/Cornerstone
mode and has a default setting of “scanning enabled”. The
MTL4841-AMS is delivered preconfigured to AMS mode and in this
mode the default is “scanning disabled”. In either case the instrument
maintenance software can be used to change the MTL4841’s
scanning mode.
Scan list
Each loop connected to an MTL4842 is added to the scan list if a
HART device is detected on power up or if the instrument maintenance
software resets the MTL4841. Loops can be added individually or
removed from the scan list using the “loop rebuild“ facility in the
instrument maintenance software.
Scanning enabled
The MTL4841 scans continuously round all loops on the scan list
indicated by the MTL4842 LED sequence.
Scanning disabled
One MTL4842 indicates the last loop addressed by the MTL4841.
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6 FAULT FINDING AND ROUTINE
MAINTENANCE
6.1 Maintenance precautions
Most codes of practice permit live maintenance on intrinsically safe
devices and systems, provided that precautions are taken to preserve
the integrity of the device or system. During live maintenance of
MTL4000 modules, the hazardous-area connectors that plug into
the tops of the modules are likely to be removed, so the cables that
connect into the hazardous-area connectors must be reasonably
flexible in order to allow connectors to be inserted and removed
easily from the module tops.
When a hazardous area connector is unplugged, care must be taken
to ensure that it is not laid in a position where it could come into
contact with the backplane or backplane components. The backplane
is connected to safe-area circuits and is therefore not intrinsically safe.
An unprotected connector could by-pass the essential segregation
between the safe-area and hazardous-area circuits. This can be
avoided in one of the following ways:
a) By plugging the connector into an MTL4099 dummy isolator or
other uninstalled MTL4000 module directly upon removal (but
NOT into any other module mounted on the backplane).
b) By providing some method of securing the connector temporarily
so that it cannot touch the backplane or the safe-area circuits.
6.2 Fault finding
When fault finding, carry out the following steps as far as is
necessary:
1) Check the condition of the installation to make sure that no
damage or deterioration has occurred.
2) Check that one, or more, of the backplane power LEDs is ON.
If not, check the power supply fuse and, if necessary, change it.
The rating is:
BPMH16/BPSH16 : 2A (Fuse kit FUS16).
3) Check that the power LEDs on the MTL4841/4842 modules are
ON. If not, check power supply fuse FUS2. Its rating is 250mA.
4) Exchange potentially faulty isolator modules as follows.
a) Unplug the hazardous-area connector.
b) Unscrew and remove the module from the backplane.
c) Plug-in and secure the replacement unit on the backplane.
d) Replace the hazardous-area connector.
Potentially faulty modules should be tested in workshop conditions,
using the following procedure:
a) Connect a power supply to a spare BPS backplane (refer to
section 4.11.3)
b) Plug the suspect module into any position on the backplane.
c) Carry out the test procedure described in the appropri-
ate section for the particular module in instruction manual
INM4000.
5) If an MTL4841 is changed, the Cornerstone software does not
recognise a replacement device until either:
a) the node name (stored within the new MTL4841) is made the
same as that of the removed device, using the software.
b) the network is restarted; when the software will adopt
automatically the node name of the replacement device.
Loop address
LED 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
A ❍ ● ❍ ● ❍ ● ❍ ● ❍ ● ❍ ● ❍ ● ❍ ●
B ● ❍ ❍ ● ● ❍ ❍ ● ● ❍ ❍ ● ● ❍ ❍ ●
C ● ● ● ❍ ❍ ❍ ❍ ● ● ● ● ❍ ❍ ❍ ❍ ●
D ● ● ● ● ● ● ● ❍ ❍ ❍ ❍ ❍ ❍ ❍ ❍ ●