MF12 3.12
5
3.0
O
PERATION
The instructions for operating the temperature controller are given in a separate manual.
If the furnace is fitted with a time switch, see also the supplementary manual MS03.
If cascade control is fitted, see the supplementary manual MS07.
3.1
3-zone Control Methods
The models in this manual are typically designed to achieve an extended uniform temperature zone
by the use of three control zones. The control zones are typically linked so that they are all follow
the central controller in a master-slave approach; there are two ways of doing this. Alternatively
independent control zones may be ordered. There are thus three control methods (A, B & C).
A.
Back-to-Back Thermocouples
This is the most commonly supplied option.
The central zone of the work tube is controlled directly by the central temperature controller. Each
end zone thermocouple is wired in opposition to a central reference thermocouple, and the small
voltage resulting when the zones are at different temperatures is used by the end zone controller.
The circuit diagram in section 7.1 shown the thermocouple arrangement.
Set the "setpoint" of the end zone controllers to zero. Alternatively, a small temperature difference
(offset) can be created by setting a non-zero value, but the sum of the main controller set-point and
the slave controller offset
MUST NOT
exceed the furnace maximum temperature. The "measured
temperature" display shows the actual offset.
To alter the setpoint (with the display at “home”), press Down
or Up
once to display the
setpoint; press again or hold down to adjust it. The display returns to the measured temperature
offset when no key is pressed for 0.5 seconds.
Sometimes a furnace using this type of control does not cool down: the end controllers try to
remain at the central temperature. Should this occur, contact Carbolite’s technical department.
2132 Slave Controller Navigation Diagram
B.
Retransmission of Setpoint using Broadcast comms
When this is ordered there are three independent thermocouples connected to the three
controllers. The controllers are linked together, the central controller communicating the desired
setpoint to the end controllers.
Additional communication modules are fitted in the controllers, rather than an additional
thermocouple as in A. The communication between the controllers of the Eurotherm 3000 series is
known as Broadcast comms.
It is possible to switch off the linked control and allow the controllers to work independently. In
level 2 of the end zone controllers (see controller operating instruction), scroll to
L-r.
Where the
end zone controller is a 3216 use the
up
down and select
NO
. Where the end zone controller
is a 3508 use the
up
down to select SP1, (SP1 = Local, and SP2 = Remote). There is no
need to alter the centre controller.
It is possible to use local trim in the end zone controllers to enter a positive or negative adjustment
from the centre zone temperature. Once entered this trim will always be added or subtracted from
Home
List
Access
List
°C/F/k
ACCS
°C/F/k
codE
0.0
Zone temperature
difference; use
/
to access offset
“setpoint”
home list
for factory access to lists
and parameters not
available to the operator
OP.Hi
Output
List
oP
power limit
setting, if
present
