MVE Biological Systems
TEC 3000 Operating and Maintenance Freezer Manual
13289499 Rev H •
84
Frost Line
Measured LN2 level
7.3.2.
Liquid Nitrogen Level Calibration
This section describes the procedure to calibrate the LN2 level. This procedure requires
the cryogenic meter dip stick supplied with each MVE freezer. This calibration method
provides level measurements with a ±0.5” (±13 mm) accuracy.
All new freezers equipped with TEC 3000 controllers have been calibrated at the factory.
The liquid level should only be calibrated if faulty readings are suspected, the TEC 3000
itself has been replaced, following a firmware update, or as a part of a preventative
maintenance schedule.
CAUTION
: Always wear protective gloves and face shield when handling LN2.
Refer to the Safety section of this manual.
Dip Stick Procedure
1. Open or remove the freezer lid to access the interior storage space.
2. Hold the meter dip stick vertically with the 0.0 inch end pointed down.
3. Lower the meter dip stick into the LN2 at the bottom of the freezer. Ensure the meter
dip stick is vertical and touching the bottom of the inner Dewar. Some LN2 boiling will
occur around the meter dip stick.
a. MVE High Efficiency / Vapor Series Freezers:
Insert meter dip stick into the rectangular channel on the turn tray in
order to access the liquid below the tray.
b. MVE Series and MVE Cabinet Series Freezers:
Lower the meter dip stick to the bottom of the freezer as close to the
center as possible to obtain an accurate measurement.
4. Leave the meter dip stick in the LN2 for approximately 5 seconds.
5. Remove the meter dip stick from the liquid and immediately wave it back and forth in
the air. A distinct frost line will begin to develop as moisture in the air condenses on
the meter dip stick predominately where it was submerged.
6. Subtract 0.5 inches (13 mm) from the observed frost line to account for the LN2
boiling up around the meter dip stick while it was submerged. This resultant level
measurement represents the actual liquid level inside the freezer. Once you have
obtained the measured level, proceed to the liquid level calibration.
Figure 11:
Meter dip stick showing example level frost line. The resultant measured
level would be 5.5 inches after subtracting 0.5 inches from the frost line to account for the
LN2 boiling.
Note: LN2 liquid at or above turn tray height will rise higher in the dip stick channel.
Содержание MVE 1842P-150
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