A&D has developed a new weighing environment logger, the AD-1687. This logger can simultaneously and chronologically record weighing values and the following environmental factors: temperature, humidity, atmospheric pressure, and vibration. This installment of the development story series explains the circumstances behind the planning and development of this product, our development goals, and the demands of the market.

As can be expected, environmental conditions that influence the performance of weighing instruments are recorded in labs that use analytical balances. This is done because the minimum display of analytical balances is 0.1 mg (1/10, 000 of a gram) or less. Furthermore, the resolution, which is the capacity divided by this minimum display, has reached 2 to 20 million to 1, and, as a result, standard weighing instruments require incredibly high resolutions and are very sensitive to their surrounding environments.

As a side note, pen recorders and recording paper were long used in manner similar to a meteorograph to record temporal changes in temperature, humidity, and atmospheric pressure. Our balance development team also used a meteorograph for a long time. However, we would have troubles recording data in this way, such as paper or ink running out and being unable to record at critical times. Another problem was that the data was difficult to handle and couldn’t be processed freely. For instance, the weighing data had to be checked using an analog readout, which made it difficult to determine the values, and the results obtained couldn’t be graphed. These issues created a demand for devices that can record various meteorological parameters digitally. Due to this demand, various types of loggers that can record data such as temperature, humidity, and atmospheric pressure were developed and are used in many labs and production facilities today.

These circumstances exist at all sites that use weighing instruments. In particular, users of weighing instruments use instruments that measure these environmental parameters in locations where balances and scales are used in order to verify calibrations of weighing values over a long period or evaluate basic performance such as repeatability by reference to the environmental data.

Meanwhile, when users at weighing sites want to link environmental and weighing data and graph the results or process the values, they find it difficult to integrate data from various recording devices. While data can be recorded to a PC to guarantee extensibility, dedicating a PC for this purpose is wasteful. In addition, special software has to be used, which makes this method complicated. There are also many other inconveniences to deal with, such as procedural rules against bringing PCs into environments such as clean rooms and security rules against bringing storage media like USB sticks into work sites.

To solve these problems, we had to find a way to collect and manage weighing data from the balance and environmental data like temperature, humidity, atmospheric pressure, and vibration from the setup environment.

Consequently, we planned and developed a logger that had never been offered before–one that can simultaneously record weighing data and setup environment data. Several years earlier, we had developed the AD-1688, a logger that records weighing data only. This time, however, we decided to develop a more advanced logger, which became the AD-1687 weighing and environmental data logger. During development of this logger, we encountered some difficult-to-handle parameters that were outside our areas of expertise, such as temperature, humidity, atmospheric pressure, and vibration. However, we solved these problems relatively easily by using recently released compact sensors that output data digitally.

When the AD-1687 is connected to a weighing instrument, weighing data (zero point and weight value) and the time, temperature, humidity, atmospheric pressure, and vibration are simultaneously recorded each time the Print key is pressed. Even when the logger is not connected to a weighing instrument, it can be used to log environmental data in locations ranging from clean rooms and labs to production facilities. In addition, by connecting the AD-1687 to a PC, recorded data can be imported into software such as Microsoft Excel for data analysis without using special data transfer software. When AD-1687 is connected to a PC, the PC recognizes it as USB storage.

The trends of the data stored on the AD-1687 can be graphed using automatic scaling and the display of environmental data for example can be limited to temperature and humidity. Furthermore, acquired data saved to a PC can be used to calculate span values and repeatability from span values. Thanks to these features, the AD-1687 is more than just a data storage device. It is a tool to proactively evaluate weighing environments.

While the AD-1687 is not tiny, it is compact and portable. To take advantage of its portability, we gave the AD-1687 heavy duty specifications. It has an IP65 waterproof construction (main unit) and enough shock resistance to avoid breakage from falls from as high as 1.5 m. We made the logger this tough because we assumed it would be used for the measurement of factory waste water and various other difficult measurement situations.

This industry-first weighing and environment logger answers the latent demands of people working where weighing instruments are used. Because of its utility, we believe that the AD-1687 offers many benefits for locations where weighing is performed and will be acknowledged as a helpful weighing management tool.

A new model with sensitivity of 1 μg has been added to the AD-4212 series of production-line weighing instruments. In this installment, I will continue the discussion from Story 2 and further discuss the development of production-line weighing instruments. Product development for the AD-4212 series moved forward with the minimum weighing value progressing in the following order: 0.1 mg, 0.01 mg, 1 mg, and 10 mg. One of reasons that the 0.1 mg model was developed first was that we had been selling a balance for production lines with a sensitivity of 0.1 mg, considered the level of analytical balances, for about 20 years as a special order item. In places where weighing at a sensitivity of 1 mg or greater is performed, the items to be weighed and the weighing jigs tend to be fairly large and heavy so we decided that ordinary precision balances sufficed and the demand for a more compact balance was low.

At the time, the new mass sensor developed for the HX Series of general-purpose balances was being used in production lines. At the time it was developed, the HX Series of general-purpose balances had excellent characteristics compared to most previous general-purpose balances, including a fast response time. Furthermore, the mass sensor that was developed at the time is still being used today in the HR Series of analytical balances, around 20 years after its release.

The HX Series was developed near the end of the “bubble economy” in Japan and boasted unusual level of high performance for the time. It was a top loader (referred to as a general-purpose or precision balance) that had a pan on top of the mass sensor, and it had a quick response speed. At the same time, it had a capacity of 100 g and a minimum weighing value of 0.1 mg, which put it in line with an analytical balance. However, because it had so many added functions, the balance was quite expensive and consequently did not sell well as a general-purpose balance. Nevertheless, thanks to its fast response and high repeatability as a production-line balance, it was adopted by fields with production lines that were said to require a weighing time of one second or less. The HX Series was held in high esteem because its fast response allowed for highly accurate weighing in moving production lines, something that production sites had been given up trying to achieve until then.

The HX Series was the first new product that I developed for the first time from the mass sensor a few years after I joined A&D. As I mentioned before, 20 years ago our sales department was quite demanding, and the product specifications ballooned during the planning stages, just like the economic bubble that Japan was in at the time. As an example, this was the first time that A&D included an internal calibration weight with a general-purpose balance. Other requests included a display section separated from the weighing section, a weighing section that could be operated via a cable, the ability to place the display section behind the weighing section, the display of weighing values on an analog display, and a communication port as standard, which was rare for a general-purpose balance at the time. As the R&D leader at the time, developing a device with these specifications as standard was a huge responsibility that required creative thinking and hard work.

In the end, we released the HX Series while meeting all the demands of the sales department, but its sales numbers as a general-purpose balance were dismal. I learned that, despite the many advanced functions available, users aren’t asking for much from weighing instruments. In other words, the HX development taught me that weighing instruments are just that, nothing more and nothing less. At the time, I struggled to meet the demands of the sales department as a product leader, but by not running away from unreasonable (or so I thought at the time) demands and making proactive proposals and responses, I feel that I was given an excellent opportunity to grow as a designer. Therefore, I am thankful for the various things brought to my attention by the sales department at the time.

This experience taught me the inevitable conclusion that users want balances that are compact, quick, and durable for production lines. For example, we ran counter to this conclusion about compactness by installing a calibration weight inside a production-line balance. Users of production-line balances that have a capacity of 100 g and a minimum weighing value of 0.1 mg do not weigh items of 100 g. The tare loaded as jigs are 100 g or less and the items weighed are several grams at most. If you think about how often calibration would be required, you realize that an internal calibration weight is not needed. And as an added benefit, you could make the weighing section that much smaller.

Let’s go into more detail about this. Many balances have a defined sensitivity drift of ±2ppm/˚C. If the capacity is 100 g and the temperature changes 5 ˚C, using the formula 100 g x 2 ppm/˚C x 5 ˚C, the drift is ±1 mg. For a 100.0000 g display, the change may be in the range of 99.9990 to 100.0010 g. If the weighing value to be confirmed is 1 g, this ±1 mg change drops to 1/100th, or ±0.01 mg. A balance with specifications of 100 g x 0.1 mg cannot detect this level of change. In other words, if the mass to be measured is within 10,000 times of the least significant digit, calibration itself is effectively no longer required, other than during installation. In production lines, if the items weighed in the line are managed separately and the weighing values are checked periodically, there is no need to stop the line for calibration.

The AD-4212B-23 has the SHS mass sensor that was developed for the GX/GF Series of general-purpose balances that followed the two generations of the HX Series. Fig. 1 is a graph of data that shows its 1 μg level of performance. The graph shows the weighing values (zero/span) obtained by raising and lowering a 1.25 g weight automatically over four days from July 8 to 12, 2011, along with the contemporaneous humidity, barometric pressure, and temperature (room temperature/internal temperature of balance).

The repeatability is indicated by the line connecting points (triangles) that represent the reproducibility (σn-1) of ten adjacent span values (capacity minus the zero point). The conclusions gained from the graph are listed below.

1. The repeatability of the span values is 2 μg or less. (The thick red line at the bottom, scale on the right axis)

2. Compared to the span values, which showed little change in the graph, the zero points changed greatly (5 mg or 5000 μg) over the four days in accordance with changes in humidity and air pressure.

3. The stability of the span values can be explained by the small temperature change of about 1.1 ˚C over four days. Furthermore, the temperature of the room was managed by air conditioning, and the area where the weighing instrument was located was separated by a partition, which meant that the air blown from the air conditioner did not influence the results.

4. The cause of the spike in repeatability at 10 AM on July 10th was determined to be the effects of a Magnitude 7.1 earthquake at 9:57 AM off the coast of Minamisanriku.

The results above showed that the SHS developed for general-purpose balances has a sensitivity of 1 μg and a basic performance level with an average repeatability of 1.6 μg. As the developer who proposed the SHS, I must say that I was surprised by the results. The SHS was developed for general-purpose balances, so a sensitivity of 1 μg, 1/1000th of the originally planned minimum weighing value of 1 mg, was amazing.

The data for Fig. 1 was obtained in our balance room. However, other data clearly shows that while repeatability is good at night when no one was moving in and out of the room, during microgram weighing blown air from air conditioning, temperature ripples, wind pressure and vibrations from disturbances caused by people moving in and out, and temperature changes from body temperatures cause instability in the display value and result in weighing errors. Details about the AD-4212B-23 were presented at the Sensing Forum held by the Society of Instrument and Control Engineers in October so I encourage people who are interested in learning more to access the published content on our website.

In the miniaturization field, which is a specialty of Japanese companies, the need for precision weighing is expected to range from research fields to production locations and grow further in the future. As a manufacturer of weighing instruments, A&D promotes the development of simple products that take the location of use into consideration, while at the same time focusing on technical support such as the evaluation of installation environments and working to expand into new markets. By providing a complete solution, we aim to improve our customers’ satisfaction with our products.

This time I would like to talk about the newly revised Japanese Industrial Standard JISZ8803: “Methods for Viscosity Measurement of Liquid”. The most significant change made this time was the addition of vibration-type viscometers as one of the standards. I would like to leave the details of the new standardization to the actual document itself or to published interpretations, and instead look at some of the background to its introduction.

The fundamental principles of the vibration viscometer were proposed a long time ago, but there were always many high technological hurdles that made its commercialization extremely difficult. As a consequence, it took around 20 years until it was finally commercialized. Meanwhile, the American car maker Ford Motors, which led the way in the mass production of car engines originally developed by a European manufacturer, first started viscosity control in its manufacturing processes more than 100 years ago. Since that time there have been various viscometers proposed and you could say the viscometer has a very long history in industrial production.

I’ll return to the new Japanese Industrial Standard. JIS standards on the measurement of viscosity were first enacted in 1959. The standards were supposed to be revised every five years, but the previous last revision occurred in 1991 so since that time more than 20 years passed without a rethink of the standards.

Naturally during this period there has been significant technological progress made around the world, and in Japan there have been major changes to society and the important industries that support it. In the field of viscosity measurement as well, the vibration viscometer has become well established as a new method of measuring viscosity during this period and its production has increased greatly. In today’s industries, many vibration viscometers can be found in use as an important tool for the management, control and analysis of liquids, in both research labs and on production lines.

Behind the development of this vibration viscometer were advances in electrical circuitry technology based on semiconductor (IC) technology, and the resulting advances in control technology, as well as the digitalization of measuring and use of computers for visualizing analysis results.

As a method for assessing the physical properties of liquids, viscosity is the most fundamental physical quantity assessed. For example, when liquids are being conveyed on a production line, flow rates, which are based upon kinetic viscosity, form an important aspect of production line control. Also, engine oil’s viscosity in response to very high and low temperatures clearly affects not only the engine’s characteristics but also the possibility of burnout. In the case of engine oil in particular, as its performance within an engine can have such a dramatic influence on reducing mechanical energy loss, and hence lead to significant improvements in fuel consumption, there is fierce competition between oil makers to develop the most efficient product.

Or when flying, consideration of the viscosity of the oil circulating in the many hydraulic cylinders of the plane’s drive-train under enormous changes of temperature is extremely important.

In applications away from the industrial uses mentioned above, the measurement and analysis of low viscosity beverages to improve their drinkability is progressing significantly. In the food sector, for such uses as developing liquid meals or barium sulfate for X-ray scanning, viscosity measurement is necessary to pursue the ease of consumption as well as the prevention of accidental swallowing. Furthermore, in the medical sector measurement of viscosity of bile or blood with a small sample quantity is required, and vibration viscometers are being regarded as particularly useful in such applications.

For the newly revised JIS, there have been two additions for vibration viscometers: the tuning fork type and the rotational-vibration type. The special characteristics of vibration viscometers are their high sensitivity and wide dynamic range, which allows them to measure a vast range of liquids, from those with viscosities lower than water to those with ten thousand times the viscosity of water. They can also measure viscosity with a sample of just a few milliliters and can perform consecutive measurements over a period of time to measure viscosity over a change of temperature. Finally, since the energy applied to the sample is minimized, the measurement can be completed in a few dozen seconds.

In the development of new materials, new methods of measurement must also accordingly be introduced. Viscosity measurement in many of the above mentioned situations was previously difficult until the development and use of the vibration viscometer. It is anticipated that the vibration viscometer will contribute to the development and improvement of substances in new fields and be further effectively used as a viscosity measurement method that sustains Japanese advanced materials technology in a variety of fields.

Lastly, I would like to add the following comments. To all those who have shared the task of completing a very wide range of JIS revisions on viscosity over a short period of approximately just one year, I’m sure you will feel a big load lifted from your shoulders. While the positioning of JIS is less clear these days, we have accomplished world-leading standardization and I would like to take this opportunity here to express my thanks and appreciation for all your hard work and efforts.

This is Part II of “Solutions provided by the BM Series”.

The BM Series of micro-balances went on sale in December 2010 (in Japan). There were 2 development objectives for this series: a standard anti-static function as a countermeasure against static electricity and verification of microgram-level measurement performance in the field. These 2 objectives can be considered proposals for solutions to potential problems in the field.

In the micro-balance market, the most important point in question is whether the measurement performance as specified by the catalog can be ensured (especially in the case of repeatability) in the environment where the balance is set up. For example, the BM-20 demands high precision and achieves a resolution of 1/ 20,000,000 with a capacity of 20 g and a minimum display of 0.001 mg. Because 1 μg is such a small mass, changes in temperature, humidity, or atmospheric pressure, slight breezes from air conditioning, and minute vibrations of support tables can negatively affect results. These external factors create instability in measurement values (particularly the zero point) at the microgram level and cause poor repeatability.

Problems pertaining to the setup environment stem from the fact that the micro-balance is so much more sensitive than its users and can detect minute environmental variations that users can’t. Since users can’t easily solve problems they can’t sense, they have a constant feeling of uncertainty about the balance. To eliminate this uncertainty in end users, we offered the Measurement Environment Evaluation Tool (AND-MEET) when the BM Series first went on sale and started to monitor actual usage environments.

AND-MEET constantly monitors the setup environment of the balance while simultaneously raising and lowering the internal mass of the balance automatically. With this tool, we were able to evaluate temperature changes and the corresponding repeatability of weighing values over time. Monitoring of the environment and weighing values helped us clearly identify errors that arise from the setup environment. It started to become clear that various issues caused weighing values to become unstable. These included large temperature fluctuations; minute repeated temperature fluctuations sensed by the balance caused by flowing air after users arrive at work and switch on the air conditioning (even when the room temperature is stable); pressure changes from opening and closing doors; and building movements caused by low-pressure drafts and distant earthquakes.

By pinpointing the causes of weighing errors, we were able to provide concrete methods to stabilize weighing values. These included introducing anti-vibration stages, setting up an external covering (breeze break) to reduce blown air from air conditioning, moving the balance away from locations where people are working and where vibrating analysis equipment is operating, and moving the balance to locations with minimal room temperature changes caused by outside air temperature. We were also able to evaluate the tangible effects of these measures.

I’d now like to discuss the measurement results acquired by AND-MEET. Figure 1 is a graph of temperature and measurement (zero point and span value (the weighing value minus zero point)) data taken over 24 hours from 5:00 PM Thursday, February 17 to 5:00 PM Friday, February 18, 2011 using a BM-22 micro-balance.

The balance was powered on at 5:00 PM on Thursday. The internal mass was automatically moved up and down in 40-second cycles and the ambient temperature, zero point, and weight were logged using the AD-1688 data logger. The ambient temperature rose from 19 to 22 °C over about 5 hours. The zero point also changed greatly after being powered on. From 11 PM on the 17th, the ambient temperature was comparatively stable, as was the zero point. Accordingly, the span value showed fewer fluctuations and stabilized.

From 9 AM to around 4 PM on the 18th, the temperature was quite stable, likely due to workers arriving and switching on the air conditioning. After 4 PM, there was a sudden temperature increase and the zero point and span value changed. This data was obtained at a university research lab that uses the balance. While the cause of the temperature changes could not ultimately be determined, the location can be described as a measuring environment with sudden temperature changes at certain times.

Figure 2 is a graph of temperature changes and the repeatability of the span value. Span value is calculated by subtracting the zero point from the weighing value. The repeatability of the span value is the standard deviation (σ) of 10 consecutive calculations.

Each point represents the standard deviation of 10 span values. The balance used to acquire the data was a BM-22, which is a micro-balance with a capacity of 5 g and a precision of 1 µg. Its specifications stipulate a repeatability of 4.0 µg with a 1 g counterweight.

From Figure 2, we can see that there were ambient temperature changes for around 6 hours after the balance was switched on and that the repeatability average was higher than 4.0 µg. After this period, it is clear that temperature changes were minor, the span value was stable, and the repeatability was at the specified level of 4.0 µg or less. After 5:30 PM on the 18th, the zero point changed due to another sudden room temperature increase and an accompanying worsening of repeatability was confirmed.

The graph provides supporting evidence for two important points when stabilizing balance performance: avoid sudden temperature changes and take sufficient time for the balance to warm up to thermal equilibrium before measurement. This is especially true for analytical balances. It is clear that it is possible to obtain measurement performance equal to catalog specifications with a micro-balance in this lab by eliminating the causes of the temperature increase after 5 PM or by measuring during the daytime, particularly in the stable measurement environment between 10 AM and 5 PM.

While the results have been omitted for space, AND-MEET confirmed worsening repeatability due to distant earthquakes and variation in repeatability over several hours due to low-pressure drafts. By providing this information, we were able to quantify the intangible anxiety users have always felt about the performance of analytical balances and also to later release the data in graphical form. This series of work has clarified problems with measurement environments and pointed the way to improved environmental setups and made it possible to measure stably with better precision. Through the abovementioned countermeasures, we hope to finally remove the doubt users have about using balances and improve usability in the workplace.

The BM Series of micro-balances went on sale in December 2010 as A&D’s flagship line of analytical balances. The BM Series was considered a flagship line not because they are the only micro-balances made in Japan. We envisioned this series being used for research, development, and analysis in leading-edge fields in Japan. Our development objectives were 1) anti-static countermeasures and 2) the documentation of weighing performance in user environments. The “Development Stories” series will describe in detail how these objectives were met, including the processes used to arrive at the solutions. This installment covers countermeasures for static electricity and the next installment will cover the documentation of weighing performance in user environments.

When we investigated the needs for micro-level weighing during the planning stage of the BM Series, we found that microgram-level measurement is currently required with the following types of samples.

1.  Minute amounts of powders in the analysis of pharmaceuticals and food additives

2.  Samples placed in plastic containers such as microfuge tubes using micro-pipettes in bio-research and the quantitative analysis of protein

3.  Samples placed on drug packing paper in pharmaceutical fields

4.  Particulates trapped by filters made of Teflon (PTFE) and similar materials to measure environmental pollutants in the air

5.  Minute amounts of liquid ejected from dispensers in production lines for liquid crystals, LEDs, and electronic parts

The use of micro-balances in such applications can be difficult because powders, plastic containers, drug packing paper, and Teflon filters can become electrostatically charged very easily. Additionally, sample weights are usually 10 mg or less, and a minimum display of 0.01 to 0.001 mg, and in some cases 0.0001 mg, is required. For reference, 0.001 mg, or 1 microgram, is one millionth the weight of a paper clip (1 g). Since static electricity can cause weighing errors of several tens of milligrams, it is impossible to weigh at the micro level without first dealing with static electricity.

The minute amounts being measured in the abovementioned micro-level weighing applications require a balance with very acute sensitivity (minimum display) and the effects of electrically-charged samples and containers make it impossible to perform accurate weighing. Micro-balances are also used to measure minute amounts of liquid, powders, and solids in production lines in clean rooms dehumidified to a humidity of 0% to maintain quality. Most clean rooms must be free of dust and metallic contaminates so material such as polyoxymethylene (polyacetal) is frequently used in drive systems to reduce both slide resistance and the release of metallic particles. However, plastic is easily charged in low humidity. For example, vials and other weighing containers can become charged during delivery, which causes unstable weighing and other problems.

To eliminate static electricity, all models of the BM Series are equipped as standard with a direct-current ionizer. Direct-current ionizers generate a large number of ions over a wide area so they do not require a fan to blow the ions, which means that powder samples do not get blown away. What’s more, the strong anti-static performance of direct-current ionizers removes static electricity from samples in about 1 second, which means the breeze break door only has to be opened and closed once while eliminating static electricity and weighing the sample. Additionally, the balances are equipped with a dedicated anti-static chamber. Users can place samples here to eliminate static electricity from all samples before weighing. This allows the user to weigh the samples one after another without having to perform static elimination before each weighing. Storing samples before weighing in the anti-static chamber not only removes static but also allows samples to acclimate to the temperature of the weighing chamber. This reduces convective flow, which can be caused by temperature differences of 1 °C or less, and in turn reduces weighing error.

On BM Series models other than the micro-balance models (BM-20/22), the plate that separates the weighing and anti-static chambers inside the breeze break is removable. Removing this plate creates a large weighing chamber that allows users to open a side door of the weighing chamber, pass the sample near the static eliminator at the top of the weighing chamber to remove static electricity, and then place the sample on the weighing pan. In other words, they can remove static electricity from the sample and then weigh it immediately. The ion-generating discharging electrodes (needles) are covered to prevent users from touching them and can be exchanged simply by replacing the unit. This unit configuration provides a level of safety that conforms to the requirements for CE marking and allows users to perform maintenance themselves.

We hope that users aware of the problems of static electricity and researchers who feel their weighing results are unstable in dry winters will effectively use the anti-static function of the BM Series to achieve more stable weighing.