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Development of the MX Series of Heat Drying Moisture Analyzers
(Moisture analyzers: MX Series)
Naoto Izumo
R&D Division 5, A&D Company, Limited

This is the fourth installment in a series of development stories and summarizes A&D’s development of a heat drying moisture analyzer.

A&D has been developing scales and balances since our inception 34 years ago and has been manufacturing weighing equipment for over 30 years. In the beginning, our low name recognition made it difficult to sell products based on the A&D brand and we often entered into OEM supply arrangements with partner companies as a result.

This was also the case for heat drying moisture analyzers where mass measurement technology is used, and we supplied only the mass sensors for a long period. Technically speaking, heat drying moisture analyzers are composed of a heater and a highly sensitive embedded balance as its mass sensor. This combination of a highly heat-susceptible balance and a heater that reaches a temperature of 800 °C presents many design issues.

Addressing these issues to suppress the temperature conditions that are so harsh for the balance requires a complete design solution. Consequently, we were concerned for many years that supplying the mass sensor elements alone limited the completeness of a product. As a result, about 8 years ago, we decided to take up the challenge of creating a product using 100% A&D technology that produced the ultimate level of performance in the environments where moisture analyzers are used.

When we were planning development, there was a manufacturer with overwhelming share and name recognition in the heat drying moisture analyzer market in Japan. This caused some within A&D to say that market reception and sales would likely be poor if we released a product under the A&D brand, no matter how distinctive it was.

Nevertheless, we held the opinion that the market always recognizes sophisticated, high performance products available at a low price and moved forward on the difficult road of product development. This included establishing our own heating technology, since our department did not possess any.

The first obstacle was the cost of the halogen heater. While there were other heating methods available, including infrared lamps and sheath heaters, we decided it was best to use a halogen heater since we felt that the demand for short measurement times would grow stronger in the future.

There were several leading products in the market that used horseshoe-shaped halogen heaters around the outside of the pan to ensure even temperatures over the surface of pan, but we found these horseshoe-shaped heaters to be extremely expensive. Alternatively, when low cost, straight halogen heaters were used, several heaters had to be lined up to heat the pan surface evenly. On top of this, no which method we used, we found it hard to heat the pan surface evenly and we were unable to eliminate uneven heating. We were also concerned that these complex constructions would drive production costs too high.

Another problem with these existing designs was that the halogen heater and the heated sample share the same space. If volatile portions soil the halogen heater, the halogen cycle might break and cause the heater to burn out or the level of heat generated might drop. Obviously, we were concerned about the problems this would create for users.

Right from the start of development, we thought that somehow a single straight halogen heater could heat the pan evenly. Looking back now, this was a quite bold proposition. At first, we considered using a reflector to reflect the light and devised various ideas for the material, surface reflection, angle, size, and shape of the reflector. Still, we were not able to prevent the single straight burn line that was left on the sample on the pan.

After reviewing the reasons why the pan surface was not heated evenly, we thought that the problem might be that the light (heat) of the heater was hitting the sample directly. Instead of using a reflector, we decided to place glass in between the heater and sample. The glass receives the light, increases in temperature, and gives off secondary radiation. Accordingly, we later named this method Secondary Radiation Assist (SRA).

Since the heat-resistant glass is under the halogen heater, it receives the light before the sample. The glass is thermally conductive so its surface heats up evenly and its secondary radiation spreads uniformly over the entire pan. While making several prototypes, we performed tests with corn grits on the pan. When the corn grits were baked evenly and the color of the entire surface changed, we realized that we were on our way to developing a new type of moisture analyzer.

Heat drying moisture analyzers produce volatile components during heating and are therefore the measurement equipment that is most susceptible to soiling. A by-product of using the SRA is that contamination sticks to the glass of the SRA instead of the surface of the heater. Since the easy-to-clean flat glass of the SRA prevents contamination, lamp exchanges are greatly reduced, resulting in reduced management costs and maintenance time.

The unit also has seven layers of insulation to protect the heat-susceptible balance from the 200 °C temperature of the pan. We were able to perform temperature correction in the optimal locations of the balance and achieve a final sensitivity of 0.001% (10 ppm). Our top-class MS70 unit has a sensitivity of 10 ppm and can be used to manage the moisture of plastic material (resin pellets) before the injection molding, which many considered impossible with heat drying methods. We consider the performance improvements of measurement equipment that resulted from the development of the MS70 to be a good example of pioneering and shaping new markets from new measurement possibilities.

We also developed Rs-Temp, software designed for product usability in basic operations and beyond. It automatically finds the optimal heating temperature for unknown samples in 30 minutes and has excellent graphical functions to visualize moisture rates in real time. This software is included as standard on a CD-R. Also included as standard is sodium tartrate dihydrate, which is provided as a reference standard for moisture rates due to the crystallization water in its molecular structure. We believe that the standard inclusion of sodium tartrate dihydrate acts as our guarantee as a manufacturer and shows our accountability for product performance.

As we have proposed and realized the above solutions at a reduced cost, the market has steadily acknowledged our success and made A&D into a recognized brand. As evidence of this, we hold an overwhelming market share in Japan for moisture analyzers with a resolution of 0.01%.

In summary, the development of the MX series of moisture analyzers has shown us that to succeed in existing markets it is crucial to challenge the status quo, pursue the necessary performance standards and underlying needs of products, and propose concrete solutions.

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