Page 6Isotemp Muffle Furnaces
Example Offset
Open
Thermocouple
Over-
Temperature
Indicator
2. While pressing the MODE keypad, place the power switch in
the ON position. The display now shows the current offset
value. The display offset values are limited to a range of +/-
30°C.
NOTE: If no keypad activity occurs within 3 seconds, the
display will return to the temperature display mode.
3. Press and hold the Up arrow keypad to increase or the DOWN
arrow keypad to decrease the offset value.
4. Press the MODE keypad again to enter the new offset value or
wait 3 seconds and the new value will automatically be
entered.
When finished, the temperature display will be updated based on the offset
value entered. For example:
A desired setpoint of 450°C is entered and the furnace is allowed 1 hour to
stabilize to the setpoint. A reference temperature is then measured inside
the chamber to be 455°C. In order to match the temperature display to the
reference thermometer, a display offset of 5 is entered. The temperature
display is then increased by 5°C and the display is in agreement with the
reference standard. The control will then cut the heater ON time down so
that the chamber cools by 5°C, thus matching the desired setpoint.
In the event the thermocouple becomes detached or broken, the display
will indicate so by showing “otc” (open thermocouple). When this
condition is encountered, the heaters are held off. Repair or replace the
thermocouple connection as needed to clear the display.
If the temperature in the chamber exceeds the setpoint by 100°C, the
display will warn the user by flashing “HIGH” along with the current
chamber temperature. Also, the safety relay will cut the heater circuit out
and de-energize the heater.
NOTE: This condition can also be created by decreasing the
setpoint 100°C lower than the current chamber temperature
Allow the unit to cool and the “HIGH” temperature alarm will turn off
when it falls to within 25°C of the setpoint. The controller will then
resume normal heater control.
