Help Screens, Temperature Thermocouple Select

TW-357 REV E

Help Screens

The Help button provides help to the user at any point in the menu system. The help message is displayed and the user is then prompted to press a button to return to the menu system.

Temperature

Thermocouple Select

The chamber temperature is monitored with 1 or 2 Type T thermocouples. The thermocouple is placed in the chamber to monitor temperature level with the top rack. Factory installation includes one thermocouple inside of the thermocouple tube at an elevation to match the height of standard racks. A second Type T thermocouple may be added to monitor another location inside the chamber. Both thermocouples can be activated/deactivated through the menu system. (MENU, 1, 1)

Calibrate Temperature

KRYOS provides easy calibration of the thermocouples. To calibrate, the user should enter the menu system (MENU, 1,2). Remove the thermocouple from the thermocouple tube and dip thermocouple #1 into an ice water bath. The fourth line of the control display will indicate “Wait” and will give a reading on the proximity of the temperature to 0ºC. When the temperature reaches equilibrium the control will indicate “OK” and the user can press the left soft-key button. Dry the thermocouple thoroughly. Next, the control will prompt you to dip thermocouple #1 into LN2. Wait while the control reaches equilibrium at -196ºC (-320ºF). When it does, the control will again indicate “OK” and the user can again press the left soft-key button. The control is now calibrated. The thermocouple is now ready to be repositioned inside the thermocouple tube. Please note that both thermocouples are calibrated by going through this process with Thermocouple #1.

Test Temperature System

The temperature circuitry can be checked at any time through the menu system (MENU, 1,3). This check will tell if the thermocouples are working or if they are “open” (broken or unplugged). If a thermocouple is not connected to the control it will check as “open.” If a thermocouple is “Disabled” through the menu system, it will not show up on the check.

Level Sensing

The level sensing in the system is determined through the use of thermistor-based sensor assemblies. Thermistors are thermal resistors whose resistances change as temperature changes. Their use in liquid level control is a time-tested method to provide accurate results. The KRYOS uses a 7-, 8- or a 4-thermistor assembly to measure liquid level in the freezer. The 4-sensor assembly provides general information about liquid level (high, normal, and low alarm) while the 7- and 8-thermistor assemblies provide liquid level readings accurate to within one inch. When the LN2 level drops below the START FILL sensor, the control opens the solenoid valve to commence the fill process. This process continues until the LN2 level reaches the STOP FILL sensor. When the control “senses” that the LN2 has reached the upper level, it flashes “Check” on the display while the KRYOS insures that it has not received false signals and then allows the fill to stop. The fill process can be halted at any time before it reaches the STOP FILL sensor by manually pressing the STOP FILLING button.

Test Level Sensors

The sensor assembly can be tested through the menu system as well (MENU, 2, 1). The sensor diagnostics indicates the sensor number and the status (whether in liquid or gas) of that sensor. If the control is set for an eight-thermistor or Freeze-Guard sensor it will indicate 8 sensors in the diagnostics. Likewise, if it is set for a four-sensor assembly, it will indicate 4 sensors. The status is indicated with either an “O” for open, a “G” for gas or an “L” for liquid. This is an easy means to tell if sensors are in or out of liquid or if a new sensor assembly is needed (open sensors).