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4. OPERATION PROCEDURE
Independent Overheat Prevention Device
DF/DH series units feature redundant safety devices: 1) The internal automatic overheat prevention
(automatic reset) feature, and 2) the Independent Overheat Prevention Device (IOPD) with discrete
power supply, circuit and sensor; completely independent of the CPU board.
The IOPD main relay functions to activate and cut power to the heater when chamber temperature
goes too far beyond objective temperature.
These functions are enabled while the main power switch (ELB) is ON.
Setting Independent Overheat
Prevention Device (IOPD) activation
temperature
※Set temperature with ▼▲ keys on IOPD panel.
Operation may be terminated by Independent Overheat Prevention Device (IOPD) activation,
when IOPD temperature setting and target temperature are less than 20°C apart.
IOPD temperature should be set at least 20°C higher than target temperature.
Note: main function of IOPD is to keep DF/DH unit from overheating, NOT to protect test samples
from damage. Likewise, it is NOT intended for protection against accident or injury resulting from the
negligent use of explosives and flammables.
Factory defaults and setting ranges are shown below:
To confirm whether IOPD functions as intended, set chamber temperature to any value within
unit specification range and allow temperature to stabilize. Gradually lower IOPD temperature
setting. If IOPD activates within 10°C of temperature setting, it is functioning normally.
Note: it normally takes 5 (five) seconds for IOPD to activate. Waiting 5 seconds each time
temperature is lowered in the confirmation test above, is therefore recommended. When IOPD
activates, error code Er07 shows in main unit display and operation is terminated.
When changing the IOPD temperature setting, a few seconds are needed for changes to
finalize. For this reason, wait 5 seconds after entering change before turning main unit off.
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