Chapter 6 – Frequently Asked Questions
Page 6-2
TestEquity 115A-EX Temperature Chamber
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 – The Temperature Controller uses a thermocouple control sensor, which is
located in the discharge airflow. Control tolerance is a measure of how much the temperature
varies 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
±
0.5°C,
or a total of 1°C. For example, the temperature set point may be –25.0°C. The actual temperature
varies between –25.4°C and –24.5°C. This corresponds to –0.4°C and +0.5°C or a total of 0.9°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.
Uniformity – Also known as Gradients. This is a measure of variations in temperature at
different locations throughout the chamber interior, at the same time, after stabilization. The
uniformity specification for this chamber is
±
1.0°C or a total of 2°C, when measured at least 2"
away from the chamber interior walls. These specifications are for an empty chamber. The
addition of a test sample may affect the temperature uniformity. For example, an energized test
sample will produce a higher temperature near the sample.
Controller Accuracy – This is the ability of the temperature controller to accurately display a
temperature measurement when compared to a standard. The controller display accuracy is
±1.66°C. However, the total measurement accuracy in the chamber includes the thermocouple
sensor wire accuracy. Thermocouple wire accuracy is ±1°C or 0.75% of reading, whichever is
greater. Therefore, total system accuracy over the chamber’s operating range can be as much as
±2.66°C, although the typical accuracy is often better than ±1.0°C.
Can I tilt the chamber to move it?
You should be able to tilt the chamber 45 degrees to move it. After tilting it and moving it into
place, perform the steps as outlined in “How to inspect the refrigeration machinery
compartment” and “How to check the refrigerant charge” before placing the chamber back into
service to make sure that no damage has occurred.
I’m not going to use the chamber for a while. Is there anything I should do to prepare it for
storage?
Perform ALL the steps in the Preventive Maintenance Schedule before placing the chamber into
storage. This will ensure that the chamber will be ready to operate when it is taken out of storage.
If the chamber has a problem and is still under warranty, these problems should be resolved
before being placed into storage, since the warranty period starts from the date of shipment. The
chamber should be stored in a conditioned environment. Do not store it outside or where it will
be subjected to dirt or excessive moisture.
I haven’t used the chamber for a while. Is there anything I should do to prepare it for
operation?
Perform ALL the steps in the Preventive Maintenance Schedule before placing the chamber back
into service. This will ensure that nothing has been damaged and that a leak has not developed.
