While explaining about our moisture analyzers, I am not infrequently asked if we have a cookbook; the interrogator implying our competitors have such sacred books that any user must see them. Such cookbooks list all kinds of materials subject to moisture determination and indicate the optimal heating temperatures along with moisture rates. Sometimes it seems to be implied that we should be dying to get our hands on these competitors’ cookbooks. If I had been asked the same question prior to the introduction of MX in June 2002, I would have replied in a totally different fashion than I would now; that is to say I would have been secretly asking if I could have a copy of such cookbooks that they might happen to have. Now I could show the interrogator the Users’ Handbook (PDF file 2.57MB) we have prepared for MX/MF-50, which has the subtitle “Test with The Best – True 0.01%(S.D.)” (I believe that it is one of the best in the industry, a well-written technical handbook from which one can learn a lot about moisture measurement though the list may not be as long as with the competitors cookbooks), but instead I half jokingly say in such cases that we don’t need a cookbook because our MX comes with its own chef. I feel this is a provocative and intriguing way of bringing the WinCT-Moisture to the table.

A typical moisture measurement at a fixed temperature follows a pattern as shown in Figure 1.
The vertical axis indicates moisture rate while the horizontal axis indicates time elapsed. Though it appears that it is going through a smooth drying process, if you look at it very carefully, you will notice that at around time 10 there is a change. Prior to time 10 the slope continues to become steeper as time elapses, then at around time 10 it begins to flatten. When the material starts to be heated, the surface reaches the set temperature first then gradually the heat permeates deeper into the center of the material. Eventually the whole mass reaches the set temperature. Prior to the whole mass reaching the set temperature, the mass dissipating moisture increases as time elapses, thus the rate of moisture loss accelerates. However, when the whole mass reaches the set temperature uniformly, the rate of moisture loss becomes proportional to the residual moisture within the material, which indicates the slowing down of moisture loss. In other words, a material goes through these two different stages at a fixed temperature, and when the temperature is raised, it goes through the same process of an accelerated moisture rate period and slow-down period.

Though almost all moisture measurements go through this kind of behavior, it is not as obvious to an observer as this one. However, if you calculate a slope or gradient of the graph at each temperature, you will see the change more clearly. Figure 2 shows the gradient calculated at each temperature. For instance, the gradient is 1.5 at time 5 and continues to be bigger until it reaches time 10 where it peaks at around 2.45, and then starts becoming lower. (Mathematically it is defined as a point of inflection.) If the set temperature is right for moisture determination for the material under test, the graph in Figure 1 flattens or stops changing at a certain moisture rate. If the graph does not enter such a state but instead it starts going up again, then it means the material is no longer losing moisture alone but going through a different chemical change like carbonation or oxidization. This is a rheological approach to analyzing materials, but RSTemp of WinCT-Moisture or OTS (Optimum Temperature Search, Patent Pending) utilizes this behavior when a material goes through heating process.

When a material has ingredients other than water that may evaporate at different temperatures, the moisture rate graph may become very complex or have multiple points of inflection. In such cases, it is next to impossible to get meaningful interpretation from the raw moisture rate graph, but the use of RSTemp may bring such complex behavior to light and lend itself to some meaningful scientific interpretation. In short, this technique enables the RSTemp to accurately estimate ideal heating temperatures for unknown materials.

I hope by now you see why I say, “Our MX comes with its own chef.” We are now adding MS-70 with 0.0001% resolution to our product offering, which may effectively cover the areas where only Karl Fischer titration type methods were viable methods in the past. However, it is important to note that RSTemp or OTS (Optimum Temperature Search) function works well only when your moisture analyzer has solid and reliable performance with fine temperature control. Without them even a chef cannot help. It is safe to say our M family of moisture analyzers has highly accurate and reliable performance because:
- Reliable weighing is made possible with SHS sensor and eight layers of insulation so the sensor is not affected by heat.
- Uniform heating is made possible with SRA or Secondary Radiation Assist.
- Fine temperature control with minimum deviation from the set temperature.
- The halogen lamp reaches the set temperature in a short period of time.
Only when these tough conditions are met, can the WinCT-Moisture work as your chef. A cookbook is a plus, but the chef that comes with MX-50 or MS-70 has the advantage that he can cook with any new materials you bring him in a timely fashion.

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