High Temp Alarm; Open Thermocouple; Calibration - Fisher Scientific 650 Series Instruction Manual

O
PERATION
Caution
Use thermometers/thermocouples
suited for operation at temperatures
equal to or higher than the desired cali-
bration temperature.
20
High Temp Alarms
All Fisher Furnaces come equipped with high temperature
alarms. When an alarm condition occurs, power to the
heaters is removed while the Set display flashes between
the current set temperature and "HI".
The high temperature alarm will activate when the actual
temperature is greater than the set temperature by more
than 25°C (45°F). The alarm condition will continue until
the actual temperature falls within 5°C (9°F) of the set
temperature.

Open Thermocouple

When the displays show "oPEn xx", where "xx" desig-
nates the last set temperature, an open thermocouple is
being detected. Check the thermocouple connection and
replace if necessary.

Calibration

To calibrate the furnace, place a reference thermometer
or thermocouple lead inside the furnace chamber located
as close to the geometric center of the chamber as possi-
ble. Set the furnace to the desired temperature and allow
enough time for the temperature to stabilize.
Note the temperature as indicated by the reference ther-
mometer. Compare it to the temperature in the Actual
display. If the two readings do not agree, press the
MENU key twice. The displays should show "0 CAL".
Use the UP or DOWN arrow key to adjust the calibration
(CAL) number to a value which will equal the temperature
of the reference thermometer when added to the most
recent temperature of the Actual display.
For Example: A furnace is set to 500°C and allowed to
stabilize. The reference thermometer indicates 505°C.
The furnace Actual display shows 500°C. The calibration
(CAL) value is set to +5 in order for the Actual display to
agree with the reference thermometer. Press the MENU
key four more times until the displays show the tempera-
tures with the Actual temperature corrected.