If you are involved with electronic and electromechanical product validation, then you must be familiar with Hot Test and Dry Heat Test as part of the environmental test.
These two temperature test procedures are explained at IEC 60068-2-1 and IEC 60068-2-2.
If we temperature test in general, running cold test and dry heat test may look like simple task to do. This may be true, especially when you have reliable, user friendly, and verified temperature humidity test chamber to run the test.
To make sure that we select the correct temperature humidity test chamber that has correct performance to run the test, we may need to pay attention to following checklist.
First, surely what we need to check is the temperature-humidity range that can be covered by the chamber. You may want to check the temperature and humidity envelope area provided by the test chamber manufacturer. If the test specification doesn't specifically mention about the heating and/or cooling rate, then we have one parameter less to take care of. If we don't need high or specific cooling rate, then air cooled system should be good enough, since it is more economical and less requirement (no need chiller) from maintenance perspective.
Second, we may want to consider the size and also how many UUT that we plan to put inside the test chamber. Pay attention that all UUT must have enough spacing between each other and also from the test chamber wall itself in order to guarantee the uniformity of the temperature subjected to the whole surface of the UUT.
Third, we may want to try to use the controller software. Ensure that the software is easy to use, easy to create a program, able to keep as many programs we need, and easy to monitor the progress of the running test. We would like also to check the compatibility of data to make sure that it's easy to extract the test result to neutral format (.txt, .csv, etc), for us to perform post processing.
Fourth, we may want to check also what kind of safety interlock have been configured in the test chamber. Some of the interlocks may include over-temperature, empty humidity water, power supply phase direction, refrigerant pressure, etc.
Fifth, we can also run trial for the extra feature provided by the manufacturer. Some of manufacturer provide feature that allow us to connect the test chamber to our PC, allowing us to control and monitor the test through our PC. It also allows the test data to be transferred directly to our PC. Some of manufacturer also provide feature that allow us to automatically power ON or OFF the UUT at certain period of our test.
Sixth, one of the most important is the verification test to ensure that the test chamber is able to achieve the performance requested by the test specification.
Commonly, the verification test needs to measure following parameters:
1. Temperature Humidity Deviation.
This is to measure how much the test chamber can achieve the target of temperature and/or humidity. Commonly, the deviation will be higher at the highest and the lowest temperature that the test chamber can achieve.
2. Temperature Humidity Stability.
This is to measure how stable is the temperature reading after reaching the target of temperature and/or humidity.
3. Temperature Humidity Uniformity.
This is to measure if the temperature can be distributed evenly throughout entire test chamber.
All these three verification measurements are commonly done in empty test chamber condition (without UUT).
Manufacturers commonly use 9 temperature sensors and 3 humidity sensors to run these measurements. Four temperature sensors plus one humidity sensor may be placed near the ceiling of the test chamber, while another four temperature sensors plus one humidity sensor may be placed near the test chamber floor. The remaining one temperature sensor and one humidity sensor may be placed in the center of the test chamber.
