14
Part number 21729, Rev 4
Using a 250 Ω resistor, the voltage drop across the resistor varies with temperature per the
following equation.
Temp (C) = - 34.75 (Vdrop) + 74.75
See the table below for representative readings.
Voltage (V
DC
)
Chamber temperature (
0
C)
1.58
20
2.15
0
3.59
-50
4.46
-80
Maintenance intervals
Maintenance item
Recommended interval
Pre-Filter and Condenser
3 months
Calibration
1 year
Battery
1 year
Door gasket and vacuum relief port
Monthly minimum
Defrost
As needed
Maintenance procedures
Air filter
In most laboratory conditions, the air filter should be inspected monthly and cleaned once every
three months. Press the top of the filter cover to release the catch. The door will swing forward
allowing easy access to the washable pre-filter.
Condenser
Anytime that the air filter is removed for cleaning, the condenser fins and coils should be
inspected for dust that impedes the flow of air over the coils. Such dust should be removed with
a vacuum cleaner. The fins on the heat exchanger are very delicate and are easily bent, so be sure
to avoid placing any pressure or impact on the fins while cleaning.
Summary of Contents for GM-ULT-1786
Page 22: ...Part number 21729 Rev 4...
