91e Controller
MC10 – 1-3
3
2.2
The 91e – Operation
When switched on, the controller lights up, goes through a short test routine, and then displays
the measured temperature and starts to control. The output light glows or flashes as heating
occurs.
The upper display shows the actual temperature measured in the furnace.
The lower display shows the "set point" or desired temperature.
One touch anywhere on the front panel lights up the three push buttons.
The Up and Down buttons allow the set point to be adjusted.
One touch of the Scroll button displays the units of temperature F or C.
A second touch of the Scroll button brings up the tunE Parameter. Self tuning of the PID terms
can be initiated with Up or disabled with Down. Normally the factory set tuning will be
satisfactory and retuning will not be necessary, but if the control action is not satisfactory with
your combination of load and temperature then you may wish to try retuning. Please call our
service department if you need advice.
A third depression of the Scroll button reveals the alarm set point AL.SP, which can be adjusted
with the Up and Down buttons. The alarm has no function when the 91 is being used as a normal
controller.
The output light OP indicates the state of the controller's output signal to the solid sate relay
(which in turn switches the power to the heating elements).
Early versions: there is no ramp-to-setpoint feature; this is indicated by there being no SP.rr
parameter as described in the next paragraph. Please do not use the Secret Key unless you need to
discover whether the SP.rr parameter is present (and, if so, to set it).
Later versions: the ramp-to-setpoint feature may be used for controlled slow heating. To access
this feature, press the Scroll button until AL.SP appears. Press the Secret key. Press Scroll until
SP.rr appears. Alter the parameter value using Up and Down buttons - the possible values are
OFF and 0.1 to 50°C/min. Press Secret key again to return to display of measured value. DO
NOT alter any other parameters without first consulting Carbolite.
3
P
OWER
L
IMIT
A
DJUSTMENT
(91
E
HL)
This describes how to set the power limit, for example to compensate for ageing in silicon
carbide elements. You are advised to consult Carbolite if you do not have instructions on how to
decide upon the correct power limit.
With the controller powered up, press the Scroll key until the display shows AL.SP.
Press the Secret Key as shown in the controller drawing.
Press the Scroll key until the display shows H.PL. (10 presses; the H.Pl parameter follows the
H.ct parameter.)
Press the Up or Down key to select a new value of Heat Power Limit, between 0% and 100%.
Either allow the display to "time out" or press the Secret Key to return to operator mode.
Take care not to alter any other control parameters.
