In a perfect world, every time we turned the power on for one of our chambers it would be immediately ready to run, to do whatever we ask of it, and we would never have to clean or care for it. However, it is not a perfect world. The fact is that chambers need preventive maintenance, and sometimes in ways that we would not expect.
Of course there are many simple things that one would expect: checking to make sure that the water connection is tight, that the drain is free and clear of any debris, keeping the window and interior of the chamber clean. Then there are some points that may not automatically come to mind.
One of these in a humidity chamber is the wet sock. If the water supply has any impurities in it, or the level inside of the reservoir is not always high enough, the wet sock material can start to become contaminated. It is easy to see because it will change color from the normal bright white to a brownish color, sometimes even looking like it has burned. This distortion can be a problem with very long tests, causing incorrect readings and shutting down a test.
The best rule of thumb is to change the wet sock material before every humidity test. If this is not feasible, at least make sure to check the material to see that it is clean - and check the water level in the reservoir at the same time. This simple 5 second check can mean the difference between a successful test and one that needs to be restarted several days into it for a problem that would cost pennies to fix.
Yearly calibration is also an important part of chamber care. Remember that the sensors are going through the same tests that your products are, and they will wear out. It is important to make sure that all sensors are reading correctly, and the easiest way to do this is with a periodic calibration. Many companies train someone in house to do this so that extra money doesn't need to be spent for an outside expert.
When cleaning the internal portion of the chamber, be sure to follow after any chemical solution with plain water. A cleaner may appear to do an excellent job, but traces of it will remain. This can cause offgassing which can change the testing results in some cases. Simply wiping with a rag damp with water after cleaning will take care of the problem.
If you are using a PC for control, check the serial connection once in a while. Sometimes things get knocked about a bit. If you use the built in screws available on most serial cables then you can insure that communication will not be broken by a bumped cord.
Remember, the better you take care of your chamber - the better it will take care of you.
Chris Peterson,
ACS / Hanse Industries
