Taylor-Wharton CS Series - Manual (Page 32)

30
CS SERIES
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 at the top
of the inventory system. Factory installation includes one thermocouple inside of
the LABS thermocouple tube or 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.
Temperature Calibration
The CS SERIES Control System uses a type T thermocouple to measure temperature
within the CryoStorage freezer. The temperature curve for a thermocouple is
nonlinear so it is important that the CS SERIES Control System have a good
calibration to provide accurate temperature readings. The temperature is traceable
to the National Institute of Standards and Technology (NIST) ITS-90 Thermocouple
Database.
There are three important reference points needed for calibration:
Ambient Temperature:
Ice Water:
0°C
Liquid Nitrogen (LN
2
): -196°C
The ambient temperature is the temperature measured inside the control box and
is used to provide temperature compensation adjustment. This is calibrated at the
factory and should not be adjusted in the field.
Ice water and LN
2
provide the reference points on the temperature curve. If these
two points are calibrated correctly then all other points (temperatures) on the curve
are correct.
The accuracy of a thermocouple is +/- 1°C or +/- 1.5% of the reading, whichever is
greater.
To check a calibration, submerge the thermocouple in ice water slurry and then LN
2
.
If readings are within accuracy specifications noted above, then the temperature
circuit on the control is properly calibrated. If not, follow the steps below to calibrate
the temperature.