COSA Xentaur COSA 9610 - Manual (Page 35)

INSTALLATION, OPERATION AND MAINTENANCE MANUAL – COSA 9610™
Page 35 of 44
3.4. T
EMPERATURE
C
ONTROLLED
O
VEN
3.4.1. Furnace temperature control unit
The zirconia cell must operate at a temperature above 600ºC. For optimal performance, a
set-point temperature of 812ºC was chosen. The oven that serves as the heating device
for the zirconia cell is made of a metal wire-wound heating element. To minimize energy
consumption, the heating element is encapsulated by glass-fibre insulating material. The
driving voltage for the heater is 60VAC. The power is controlled by a separate
microprocessor based temperature controller. This will prevent oven failures due to
computer malfunctions, and at the same time releases computer-time for calculations and
graphical tasks.
The temperature controller utilizes a PID algorithm to drive a solid-state relay, which on its
turn controls the on/off ratio of the voltage to the heater element. To generate alarms,
and to enable the system to compensate for temperature changes, the temperature
controller has a retransmit output, which generates a voltage of 0-5V between 0-1000ºC.
The oven temperature controller is located inside the electronics compartment. It is the
controller on the top left side. All settings are factory programmed and do not need to be
changed. However, for servicing purposes it can be useful to change the temperature of
the oven. The temperature controller has two displays. The top display shows the actual
oven temperature. The bottom display shows the temperature set-point.
By pressing the up arrow key, one can increase the temperature set-point. By pressing the
down arrow key one can decrease the temperature set-point. The oven needs about half
an hour to heat up to 812ºC. Normal on/off-ratio is about 85%. This allows for a stable
temperature control and long lifetime of the oven (typically 2 – 8 years).
Photo of temperature controllers located in electronics compartment