Chapter 7 – Frequently Asked Questions
TestEquity 101H Temperature/Humidity Chamber
Page 67
Chapter 7 – Frequently Asked Questions
Why does my chamber heat or cool slower than the published specifications?
Performance is significantly affected by the characteristics of your test sample. Factors include
size, weight, material, shape, and power dissipation if energized. The test sample should be
placed in the chamber in a manner that allows for air circulation. You should not place the test
sample directly on the chamber floor. It should be placed on the shelf. Multiple test samples
should be distributed throughout the chamber to ensure even airflow and minimize temperature
gradients. If necessary, an additional shelf should be used to evenly distribute the load. You can
determine if the chamber is operating properly by following the procedure in “How to verify the
chamber performance”.
How can I modify the chamber to cool faster or colder?
Unfortunately, there is nothing you can do to improve upon the designed-in performance.
TestEquity does NOT recommend using CO
2
or LN
2
in this chamber to achieve colder or faster
cooling due to reliability and safety considerations, so it is NOT an available option. Modifying
the chamber to add CO
2
or LN
2
will permanently damage the chamber and void the warranty.
Why is there water/ice/snow in the chamber?
Any time the ambient air is subjected to temperatures below the dew point, moisture will
condense out of the air. The effect is ice or frost during low temperature operation. When the
chamber is heated above 0°C, the ice or frost will turn into water. To avoid moisture
condensation, make sure the port plugs are inserted at all times. Also, avoid opening the chamber
door while the chamber is operating at temperatures below room ambient. When a low
temperature test is completed, warm the chamber to at least room ambient before opening the
chamber door and before removing your test sample. A condensate drain is provided to remove
condensate from the chamber.
My test specification requires convection heat only. Can I turn the circulator motor off?
NO! This will damage the heating and refrigeration systems and void the warranty. You need a
“gravity convection oven” for that kind of test.
How accurate is the chamber?
That’s a loaded question! There is no “chamber accuracy” specification as such. The answer
requires an understanding of several performance parameters.
Control Tolerance – Control tolerance is a measure of how much the temperature varies over a
short term, after stabilization at the control sensor. It is a measure of the relative variations, NOT
the absolute accuracy of the readout. The control tolerance specification for this chamber is
±
0.3°C, or a total of 0.6°C. The actual temperature where the controller settles might not be
arithmetically within the center of the total 0.6°C deviation due to the characteristics of
proportional control systems. For example, the temperature set point may be 23.0°C. The actual
temperature varies between 22.8°C and 23.4°C. This corresponds to –0.2°C and +0.4°C or a total
of 0.6°C of RELATIVE variations. These specifications are for an empty chamber. The addition
of a test sample may affect the control variations. In some instances, the test sample will reduce
these variations.
