Developing an Analyzer for Use with Weighing Devices

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We have already reached No. 20 in our series of “Development Stories” which we started one and a half years ago. At that time, we had intended for all our developers working on different projects to each contribute an article to the series. However, even after making requests to them we sadly received no submissions. So it was left to me, as the person responsible for managing new product development, to summarize the stories behind product planning and decisions on product specifications.

This time I will be talking about a device to be used on the job site in tandem with our electronic scales and balances for easy measurement device management: the AD-1691 Weighing Device Analyzer. In order to clarify the purpose of developing this new instrument, I will first explain some of the background behind its development before I get into the main subject of the device itself.

Electronic balance technology is based upon mechatronics, a field of engineering comprised of many different elements. To be precise, it is an amalgamation of (1) mechanical technology to build the mass sensor unit, (2) electronics to achieve the high resolution of the balances, and (3) software technology, which is gaining more and more in importance. You could say these three elements balance each other in order to produce a high performance set of balances. However, recently we have reached the age where it is possible, with the purchase of a high precision electrical discharge machine (also called a wire cutting machine) or a machining center, to make copies of machine parts to a certain degree of accuracy oneself, not to mention electronic components.

What I am trying to say is that the measurement devices industry is now entering similar circumstances to those of the home electrical appliances industry. In other words, together with (1) economic globalization, Japan’s traditional strength of (2) essential component technology is flowing overseas. This essential component technology is becoming (3) black boxes, and by mass production in low-labor-cost countries, products that use those black boxes can now be produced as (4) low cost products and we are beginning to see an (5) influx of these products into the Japanese market. This means that by assembling these black boxes that constitute each component, in a similar fashion to the computer industry, anyone that can build an external case is now able to produce a commercial product in any part of the world.

These present conditions recall memories for me of when I first started my career 30 years ago. When I first started work the Japanese economy was carrying all before it and particularly in manufacturing technology Japan’s productivity was incomparable.

At the Harumi International Exhibition Center at that time, highly productive robotic equipment was the star exhibit at the trade shows there. These shows were extremely popular and many companies would be exhibiting such robots. The crowds were such that often you could only move together with a wave of people and at many times it was quite an unpleasant squash. As the years passed however, nearly all robotic manufacturers went out of business. This was a result of price wars between robotics makers, where a few companies cornered production of the essential parts, such as motors or control boards, and a similar phenomenon of production using black boxes occurred.

The robot boom of 30 years ago was mainly restricted to Japan; however you could say that we have presently entered an age where markets all move to the same standard criteria all around the world. What Japanese businesses will now have to bet their futures on is establishing creative new product planning capabilities which can create entirely new markets around the world, together with the essential component technology that will support this. That is to say, in order to survive Japanese companies will have to put their present technology and capabilities to use for innovative new product planning and development. You could also say these future strategies will have to preempt potential demand in existing markets.

To take the case of the weighing devices industry, the mass sensors of strain gauge-type load cells or analog-to-digital converters, which convert analog output from load cells to digital data, are already being sold as separate units in the market. In Asia, device makers in Japan, Korea, Taiwan, China, and as far away as Eastern Europe are all producing weighing machines with the same specs. Under these types of market conditions, balance makers from developed nations with more advanced technology might usually work on improving the functionality of the screen display or giving the device a more upscale appearance to continue to discriminate it from competitors’ products. That could be done by adding a large color liquid crystal display or touch panel functionality like a smartphone.

Developers would probably receive a lot of praise from sales reps for the enticing novelty factor of such new features. Most distributors in Japan and overseas, and even most of our own sales team, would probably share the opinion that we should follow this trend.

However, the requests we get from weighing device users on the job are quite simple: they want measuring to be (1) precise, (2) quick, (3) simple, and (4) low cost. If we were to focus solely on more aesthetic aspects of design, features like a fancy display would naturally lead to a larger device, more difficulty of use in the workplace and an increased price: all developments which of course would not be beneficial to users.

On the other hand, for people responsible for managing measurement devices we could speculate that introducing new management methods for weighing devices is essential due to a tightening of regulations. I am talking about people engaged in measurement work who, for example, might be responsible for the management of the production line or all the measurement devices at a pharmaceutical company, in a research and inspection company contracted to clinical laboratory tests, or have responsibility for the maintenance of measurement devices at some company. The sales team and field engineers within our own company would also fall into this category. To come to the point, there are two different viewpoints for people who work with measurement devices: those who handle them regularly in their everyday work activities, and those who are responsible for the management of such devices.

It’s an obvious point, but naturally people whose business purposes differ will also be making different demands regarding their workplace tools. People who are using measurement devices in their normal workday will want devices to simply display the measured values; people with responsibility for managing such devices will be more interested in making difficult management tasks including determining “uncertainty” easier.

Considering these points, we came to the decision that we should develop an analyzer for use with weighing devices as a tool for professionals, while keeping the configuration of the weighing devices themselves simple. To be more specific, we have developed the AD-1691, a purpose-built analyzer that can connect to all A&D scales and balances that have telecommunication functions.

For your reference, I have presented the resulting graphs of 24-hour monitoring we did with the AD-1691 (AND-MEET*) to measure the performance of our microbalance. In Fig. 1 you can see the front display panel of the AD-1691. It uses a colorful touch panel for data retrieval in an interactive fashion. In Fig. 2 you can see the readings for the microbalance’s repeatability, which averaged 2.8 µg over the 24 hour period. I won’t bother to explain all the details of the results here, but this example demonstrates how the AD-1691 can evaluate a balance’s repeatability performance while taking factors arising from the measurement environment into consideration at the same time.

AD-1691 display panel
Fig.1: AD-1691 display panel
AND-MEET results
Fig.2: AND-MEET results

The AD-1691 uses A&D’s unique Digital Signal Processing (DSP) technology, which you could think of in easy terms as a PC for specialized use with weighing devices. Using the AD-1691 it is possible to manage multiple balances. It has the functions of (1) data collection and calculations, as well as data file creation, for repeatability measurements; (2) data sharing with standard PCs using a USB flash drive; (3) determining the level of uncertainty of a balance at the location of use; and (4) presenting AND-MEET’s results in graph form. Further, there is no need for any additional software (including any special OS) when using the AD-1691 and the above functions can be performed simply by directly attaching it to the weighing device with an RS-232C transmission cable.

By using these features of the AD-1691, uniform control of multiple weighing devices can be easily achieved. It is also possible to avoid problems with connecting to computers or a lack of compatibility or uniformity with old measurement data from obsolete devices. As it has a guidance function in the interactive mode, if operator guidance is followed, the troublesome task of determining uncertainty, which involves many factors, should be able to be dealt with easily by the user on the spot.

By using this first of its kind specialist weighing device analyzer I believe significant increases in productivity can be achieved in weighing practices and it can contribute effectively to new levels of quality control.

*1 For information on AND-MEET, please refer to Development Story 12

Things to Keep in Mind when Using Analytical Balances (Proper Handling Edition)

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Analytical balances are very sensitive. Therefore, they are heavily affected by the environment in which they are installed and the way measuring personnel handle them. With regards to methods for assessing the environment, running AND-MEET (*1) will yield a judgment and assessment, and from there a concrete process for improving the environment can be proposed. In addition, in “Development Story 17”, I explained a method for selecting a location for measuring instruments. So, for this edition of “Development Story”, I will discuss proper handling with a focus on analytical balances.

The basic motto for weighing instrument operation is “quick and accurate”. So in the case of someone taking time to slowly open and close a breeze break door, these words would tell us that such is not an optimal way of conducting measurement. It means that by increasing the time that the breeze break door is open, the air within the breeze break changes, and the weighing area’s temperature will change. From amongst the analytical balances, I will use the microbalance, capable of measuring 1 millionth of a 1 yen coin (1 gram), as an example.

For instance, in bioscience research fields, many labs use micropipettes. Even with pipettes, we know that without accurate and experienced handling, random errors occur, and if there is a problem with the pipette itself then systematic errors can occur. The minimum capacity for a micropipette is around 1 to 2 μL. 1 μL is an extremely small amount compared to what we are used to in our daily lives. However, if 1 μL of water is converted into mass, it becomes 1 mg, and a sensitivity of 1 mg is a minimum display for general-purpose precision balances in the weighing instrument industry. Yet microbalances can measure 1/1000 of this unit – an ability to measure where 1 digit = 1 μg is stipulated. In other words, determining 1 μg is more difficult than using micropipettes, so it can be said that it’s clear that experience and accuracy are demanded in measurement operation.

Electronic balances deliver weighing results via digital display: from general-purpose balances with a minimum display of 10mg or 1mg to analytical balances with minimum displays of 0.1/0.01/0.001mg. Because of this, people think that if the weighing sample is simply placed on the pan, an accurate weighing result will be displayed instantly. However, with readability that is orders of magnitude more precise than the minimum capacities of micropipettes, one must question whether the result displayed is really correct, and recognize that instability in the displayed result can be quite natural depending on how the instrument is operated.

Therefore, I will explain how errors in weighing occurred using actual examples from weighing sites.

1) Effects of static electricity

For weighing instruments used in production lines using automated machines or at sites conducting plastic injection molding, there have been instances of displays becoming unstable, or measurements changing in one direction with the passage of time. This phenomenon is called “drift” in the weighing industry. Currently, in the production processes for pharmaceutical manufacturing, primary and secondary batteries, electronic parts such as IC chips and LEDs, and resin molds, many weighing instruments are used for quality control. But on these production lines, the environment is usually like that of a clean room, and we have confirmed many areas with 24-hour air conditioning and humidity levels sometimes below 20% due to the undesirability of moisture. In other words, it is dry, and friction from insulated material caused by the moving around of objects causes static electricity to build up easily. Moreover, people working on the line or research can sometimes build up around 10,000 volts of electricity themselves. Under these circumstances, the effects of static electricity become greater, and errors of a few dozen milligrams can easily occur. (*2)

If the humidity in the weighing instrument’s installation environment cannot be increased over 40% or if electrical build up occurs faster than electrical discharge, please introduce a static eliminator and conduct weighing operations after actively removing charges from the weighing sample.

2) Effects of temperature

Let’s say you check the quality of a molded item right after resin molding it by measuring it on a weighing instrument, or you measure out some pharmaceuticals into a handheld vial and then weigh it, or you take a sample from another location and bring it in to measure it right away. In scenarios like these, a difference between the weighing sample’s temperature and the weighing area’s temperature will occur. This temperature difference will become a weighing error. The reason for this is that when the sample’s temperature is higher than the room temperature, a layer of warmer air is created around the sample, and a slight upward air current is created. That air current has the effect of pushing the weighing sample up, and the weighing measurement will come up light at first. When the sample later reaches room temperature, the original weight will be displayed.

It depends on the temperature difference and the shape/material of the sample, but weighing errors on the order of a few dozen milligrams can occur.

thermograph image
Fig.1 Thermograph image of a container after being gripped by hand

Fig.1 shows the results of thermograph observations of a coffee can placed on an analytical balance. The can has been gripped for a few dozen seconds before being placed on the pan. Metal is especially conductive of heat, and a deviation from ambient temperature of a few °C can occur in a short period of time. It is known that the convection current generated by this temperature difference will affect weight measurements. (*3)

I experienced this personally more than 10 years ago, when we were setting up mass production of weights with tolerances conforming to the OIML Class E2 standard and compositions conforming to the Class F1 standard. In this instance, we found that our weight-adjusted 200 g weight had grown heavier on a 0.1 mg level the next day. We had touched the weight with gloves, but after conducting weight adjustment and screw tightening, we found that our body heat had warmed up the weight slightly. It was a good experience for me to understand why people say it is not good to touch weights directly with one’s hand. In places where weighing instruments are being used, one may see people picking up weights with gloves and calibrating, but at least when it comes to analytical balances, we recommend doing calibration and performance checks using tools such as tweezers.

3) Effects from work in the weighing area

Analytical balances come standard with a breeze break. It’s there to stop drafts and maintain stability within the weighing area. However, if the breeze break’s door is operated roughly, an impact will occur at the end of the swing and the force will reach the balance’s weight sensor. This can result in variations in the zero point, and risks reductions in repeatability. But if the door is operated too slowly, the time when the door is opening and closing lengthens, and the air within the weighing area will be replaced. As a result, the temperature can become unstable and become another factor in the reduction of repeatability.

People’s hands exceed room temperature, and placing one’s hands in the weighing area can cause a disturbance in temperature. For this reason, the door should not be opened longer than necessary, the door should be operated accurately within a short period of time, and long tweezers need to be employed to avoid placing one’s hands in the weighing area as much as possible.

As an aside, I’ve searched far and wide for an off-the-shelf set of long tweezers that are usable for calibrating weighing instruments. However, I was unable to find anything fitting the description. It was then that I independently drew up plans for an ideal set of tweezers, and gave the manufacturing contract to a manufacturer near Tsubamesanjo in Niigata Prefecture. In the production of these AD-1689 tweezers, special regional production techniques that made Japan the #1 producer of eating utensils such as spoons and forks have been used. The original “monotsukuri” (craftsmanship, artisanry) techniques found throughout Japan contain skills passed down by craftsmen for more than 150 years, and it is thought that these techniques have supported Japan’s economic growth from the Meiji Restoration to the present day. I believe that continuing to support these techniques is absolutely essential to maintaining the Japanese economy going forward.

  • But I digress. I’ve summarized weighing instrument operation methods in a simple form below.
  •  When conducting weighing using a balance, special care must be taken with regards to the weighing sample’s static charge and temperature.
  •  It is especially necessary to actively introduce a static eliminator to take care of static electricity trouble in dry environments with humidity of less than 40%.
  •  For the weighing sample as well, care in controlling the temperature is needed, including measures such as not touching the sample directly with one’s hand. It is important to place the weighing sample in the weighing area beforehand, and allow it to adjust to the temperature there before commencing weighing.
  •  Weight measurement should be conducted quickly and accurately, the weighing area door should be opened as little as possible, and one’s hand should not be inserted into the weighing area.

Reading the precautions above, one may feel heavy with the difficulty of operating an analytical balance. However, please rest at ease. Lately, multiple analytical balances with internal static eliminators are on the market. Additionally, there are models which feature a weighing preparation room where the weighing sample can be placed to allow it to adjust to the temperature. And there is also the set of long tweezers for weighing operations which I wrote about.

Regarding precautions aside from weighing operations, it is necessary to connect the balance to a power source the day before weighing to ensure that it is stable. In the case of weighing instruments at the semi-micro level and below, it can take from 6-8 hours for a connected machine to completely adjust to the room temperature. Additionally, one must do as much as they can to ensure that vibrations, pressure changes, temperature changes and humidity changes do not occur in the weighing room. As part of this, foot traffic in and out of the room should be reduced as much as possible.

Lastly, regarding handling of weighing instruments, the characteristics of electronic components of electronic balances become more stable the longer the instrument is hooked up to a power source. The thermal distribution within the device, including the weighing chamber, will become even. Since these instruments do not use much electricity, I recommend continuous connection to a power source if possible.

I believe that going forward, weighing instrument manufacturers shouldn’t just conduct development that’s all about how good the performance is or how many features there are, but that they should also come up with solutions which are easier to use on-site and which also include peripherals to display and reduce weighing errors. Moreover, this proposal means providing a comprehensive weighing and measuring service with everything from analysis to assessment, using environmental measurement, communication utilities, data management, graphing functions, and more. What is important to manufacturers at such a time is knowing the weighing and measurement market that forms the actual usage locations for these instruments. I would like to continue emphasizing market surveys and providing original products according to principles emphasizing the best results for all parties involved.

*1 Regarding AND-MEET: Please refer to the 28th Sensing Forum: Investigation of the Basic Performance of Analytical Balances (PDF 1.28MB)
*2 Regarding the effects of static electricity: Please refer to Training Material for Balances (1) (PDF 437KB)
*3 Regarding the effects of temperature on weighing samples: Please refer to Training Material for Balances (1) (PDF 437KB)

Things to Keep in Mind when Using Analytical Balances (Installation Environment Edition)

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In this edition, I want to talk about the installation environment for analytical balances, which have seen a lot of trouble on the market. In the next edition, I’ll be talking about how to properly use an installed analytical balance and take measurements accurately, using knowledge gained from actual usage scenarios.

Because analytical balances are very sensitive, the environment in which they are installed will affect them a great deal. For the same reason, we know that the way in which operators handle the balances also has a large effect. As far as assessing the measuring environment is concerned, thanks to our measurement environment evaluation tool option “AND-MEET” (*1) and our market response, it’s possible to get a clear idea of how to improve the measuring environment from a balance installation environment assessment. So for this edition, I’ve put together some general information about installation environments.

Since the March 11 Disaster, we continue to have frequent earthquakes in eastern Japan. This is a special concern for analytical balances capable of measuring on a microgram level, for not only do they pick up earthquakes, but also things such as movement of people, handcarts, and forklifts, as well as vibrations and changes in room air pressure from the opening and closing of doors.

As for weather effects, the force of wind from passing low pressure systems like monsoons and typhoons can cause problems due to buildings shaking, which becomes an even greater issue on higher floors. Buildings built with a quake-absorbing structure, which have become more common recently, are designed with shaking as a given. Such structures can shake for days due to wind pressure or earthquakes.

For situations like these, we have confirmed that passive anti-vibration tables such as the AD-1671 improve issues with repeatability. On the other hand, we have found that despite their high cost, active air suspension anti-vibration tables used for optical measuring instruments actually become a source of vibration, and negatively affect analytical balances.

Administrators of balances often ask us about the permitted specifications of an installation environment for an analytical balance. A&D recommends the following: (1) daily fluctuation of temperature of 4°C or less (within 10 – 30°C) and short term fluctuations of 0.2°C/30 minutes or less, (2) daily fluctuation of humidity of 10% or less, and (3) daily fluctuation of air pressure of 10 hPa or less. In particular, regarding the short term temperature fluctuations written about in (1), it is known that the repeated slight changes in temperature caused by air conditioning have an especially destabilizing effect on balances’ zero-point display. To cite an extreme example, our data shows that even within the sort of windy environmental setup specified by the Ministry of the Environment’s Manual for Continuous Monitoring of Air Pollution (a.k.a. PM2.5), using the AD-1672 tabletop breeze break (which surrounds the balance area) can have such an improving effect that catalog specifications for the microbalance can be met. (*2)

Allow me to explain proper installation of a balance using an actual example. Fig. 1 is a rough sketch using the seminar room in our R&D center’s 2nd floor as a model. The seminar room is about 10 meters long on each side, and there are multiple air conditioning units in the central area of the ceiling. It would be rather large for a lab, but it resembles many labs in terms of the layout of things such as the air conditioners and lab tables. I’ve numbered the tables in this diagram from #1 – #16. I would like you as well to think about which spot is the best place in the seminar room (lab) to install a balance.

laboratory layout
Fig. 1 – Diagram for evaluating balance placement

To select a location for the balance, first we must find a location that minimizes temperature fluctuations, which have the greatest effect on balances’ performance. To be more precise, a place that is (1) out of direct sunlight and (2) far away from air conditioner vents. Next, we select a (3) corner of the room next to the wall. The center of a room has weaker construction, and the floor tends to shake more easily. However, there tend to be structural supports in the corners of a room, and they tend not to shake easily. In addition, even if room temperature is being controlled at a certain level, floors and walls often go below room temperature, especially during winter. Level temperature means that the temperature is evenly distributed (the flow of heat is even), but in the case of walls which have outside air on the other side, balances near that wall may be constantly subjected to outside temperature variations. For the same reason, installation should not be done near window glass. That is why it is best to (4) install the balance near a wall which has another room on its opposite side. As for the table on which it is installed, (5) a hard balance table with high heat capacity should be used, and (6) the balance table should be separated by a few centimeters from the wall and other tables in order to isolate it from heat and vibration coming from the wall and floor. A (7) dead end area with low foot traffic should be selected because people tend to come and go through the central part of a room. To further reduce people’s influence, (8) an area far away from the door should be used, on a table where (9) only measurement is conducted in order to prevent vibration from people’s actions from affecting the balance. Additional preconditions are that the room and wall where the balance is located should be (10) far away from routes with high traffic or heavy objects moving, and (11) on as low a floor as possible.

Using the above conditions, we can determine that within Fig. 1, the best areas in the room to place a balance are #3 as well as #2, the areas where the effects of direct sunlight are low, air conditioner vents and windows are far away, routes where people move and doorways are far away, and near an area where structural materials such as supports are installed. Issues with #3 include being near a wall to the outside, and near a wall to a hallway, but I believe that will not be an issue because only people pass through the hallway.

The above constitutes a general assessment of balance installation environments, but labs often have individual circumstances, such as having a heat-treating furnace, or there being a lot of people coming and going during the day, and so on and so forth. Ultimately, running AND-MEET in the locations where balances are to be placed, assessing the environment there, making any problems clear and developing concrete measures to deal with them is thought to be the best course of action.

To sum up the above, here is what is required of a balance installation environment.

  • Be especially sure to consider the room temperature stability, and do not place a balance near an air conditioner vent in order to reduce the effects of temperature variations. If there is no other option, then utilize things such as tabletop breeze breaks or partitions to cut off direct wind.
  •  The balance should be placed in an area out of direct sunlight, away from routes people use and away from persons working on other things. To minimize the effects of vibrations, the central area of a wide floor should be avoided, and an area near the building’s supports should be selected. At this point, the balance table should be separated a few centimeters from walls and supports in order to isolate it from vibrations and heat from the building.
  •  To reduce effects from vibrations, the balance should be placed in a location as far as possible from paths for moving heavy objects.
  •  The building will shake when low pressure systems cross the area, so install the balance on as low of a floor as possible. In addition, to reduce the effects of the building shaking due to earthquakes and vibrations, an anti-vibration table should be installed.

40 years have passed since the balance was transformed into an electronic device using microcomputers. Since then, digitalization has progressed, and the balance has come to be regarded as an instrument which can be easily used by anyone. However, at present, analytical balances have a resolution of 1/20,000,000 or more, and a certain level of skill and preparation is required to enact exact measurements. In particular, with regards to balance installation, there are many matters to be taken into consideration. I hope this article will help you understand the best environment, install the machine and set up the environment, and allow you to conduct reliable measuring work.

*1 Please refer to Development Story 12: Solutions Provided by the BM Series Part II
*2 Please refer to the 28th Sensing Forum: Investigation of the Basic Performance of Analytical Balances (PDF 1.28MB)

Developing the New HR-AZ/A Series Of Analytical Balances

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A&D released the newly developed HR-AZ/HR-A series of analytical balances in January 2012. Before discussing the development of these analytical balances, I’d like to talk about the definition of an analytical balance.

In the measurement instrument industry, all weighing instruments are called “scales”. Within the category of “scales”, instruments that have a fulcrum in their mass sensor section and a mechanism to balance the object being weighed via the fulcrum are defined as “balances”. Balances can weigh the lightest weights among weighing instruments. A high resolution (capacity divided by minimum display) can be achieved thanks to the mechanism to counterbalance the object via a fulcrum and return the beam that is supported by the fulcrum back to its original balance point – a function commonly called the zero method.

There are two types of balances: general purpose and analytical. Generally, general purpose balances have a minimum display of 1 mg or larger and analytical balances have a minimum display of 0.1 mg or smaller. Incidentally, minimum display is expressed as “dig” and analytical balances express their minimum display in the following manner: “1 dig = 0.1 mg”. Traditionally, one finger, or digit, was used to express a minimum unit. “Digit” was shortened to “dig” and used to express the minimum display digit for balances.

As you know, standard analytical balances have a capacity of 200 g and a minimum display of 0.1 mg. For example, weighing in the pharmaceutical industry for Chinese herbal medicine and Western medicine is performed with a minimum display of 10 and 1 mg, respectively, so balances have historically been required to have one more digit of precision in their measurement performance, or 0.1 mg.

Let’s consider the resolution of a standard analytical balance like the one above with a specification of 200 g × 0.1 mg.

   200,000 mg ÷ 0.1 mg = 2,000,000

In other words, this analytical balance has a resolution of 2 million to one. The resolution of measuring instruments is usually around 0.1 to 0.01%, which is a resolution of 10 thousand to 1. For example, even a micrometer of a mechanical contact method, the resolution is merely several hundreds of thousands to one.

We can better understand the high resolution of an analytical balance using length as an example. The distance between Tokyo and Osaka is 500 km. Therefore, 1 dig at 2 million to one can be calculated as follows:

   500 km = 500 × 1000 m ÷ (200 × 10,000) = 0.25 m = 25 cm

Accordingly, this balance can be said to have the ability to measure the distance between Tokyo and Osaka in increments of about 22 cm (or the distance between an outstretched thumb and little finger).

If we used Mt. Fuji as an example, the increment is as follows:

   3776 m ÷ (200 × 10,000) = 0.019 m = 1.9 cm

In this case, if we were to slice Mt. Fuji by height into 2 cm slices (about the width of a thumb), the balance would be able to detect each slice. From these examples, we can see that determining the minimum display digits of an analytical balance is not easy.

After that slightly long introduction, let’s return to the development of the HR-AZ/HR-A series of analytical balances. As we mentioned in another installment, the current HR series was developed around 20 years ago as our first top-loading analytical balance. At the time, an analytical balance meant an instrument with a large mass senor in the back and a weighing chamber in the front. This type of balance had an extremely large mechanism so it had a high heat capacity and the magnetic circuit to generate balancing power was powerful so its lever ratio was small. Because of its high thermal stability and performance, it is still well regarded as a high-precision analytical balance. In terms of sales volume, however, the top-loading, general-purpose balance systems that first came out 20 years ago are now mainstream items even in the case of analytical balances.

The HR series, which pioneered top-loading analytical balances, became a very long-selling product that continues to sell today, even after its contemporary competitors have long since disappeared. However, it is true that as the years have passed, its liquid crystal display and overall design have made it seem a little old. Furthermore, analytical balances are involved in a fierce price war outside Japan, particularly in Asia, and the HR series has long been due for a price and feature refresh.

Under these circumstances a long development process started. Since the cost of developing a new mass senor would be in the hundreds of millions of yen, I initially thought it would be best to repurpose an existing sensor. I came to the easy conclusion that if we reused a sensor, it would be relatively easy to come up with a new product in terms of time. Consequently, we started development of a new analytical balance with 1 dig at 0.1 mg using the C-SHS mass sensor developed for general purpose balances. The C-SHS sensor developed for the FZ-i/FX-i series has excellent span stability and other performance features, and I thought that it would be possible to get the performance we needed quickly.

However, once we started, we struggled hard to achieve reproducibility at 0.1 mg. When I look back now, I can see that I didn’t realize that we needed to develop breakthrough technology in two areas: the sensitivity of the machine parts that make up the sensor and the electronic circuits of existing general purpose balances.

We spent hours achieving basic performance. We changed the way we processed parts to overcome processing limits and tested repeatedly to limit the variation caused by the individual differences in characteristics of the electrical parts. After repeated confirmation testing and discussions, we managed to reach our product goals. Nevertheless, it took three full years from the start of development to reach the sales stage.

While I had plenty of experience developing new products by this time, when we hit the required level of performance after a long period of resignation among the development team, it felt like we had finally found the light at the end of a long tunnel that we thought was a dead end.

HR-AZ/HR-A Series

For the newly developed HR-AZ/HR-A series of analytical balances, we raised the capacity of the existing HR series of 200 g to 250 g and achieved a high-speed response with real-world weighing stabilization of 2 seconds. For the display, we used a reverse-backlit LCD for visibility of weighing values in low light settings. The AZ series uses a highly reliable internal calibration weight mechanism that employs a unique operation method. The breeze break comes as standard and detaches with one touch for ease of cleaning and operation without a breeze break. Furthermore, all components of the breeze break are made of plastic and coated with a durable antistatic coating. These features were added to solve two issues: static electricity, the most troublesome aspect of using an analytical balance, and requests for a glass-free product, which is required for medicine and food production lines subject to FDA/HACCP regulations.

The breeze break also offers installation advantages, such as the ability to set up the balance with its rear surface close to the wall, since its doors do not come out at the rear of the balance when the side doors are opened. In addition, the balance can be embedded in an automatic production line and placed in a particular isolated space thanks to the one-touch, removable breeze break and the compact size of the balance.

While it took longer than expected to develop, we believe we have created a balance that is unprecedented in price/performance ratio, simplicity, compactness, and usability. As a result, we expect the new HR-AZ/HR-A series of analytical balances to offer users a number of convenient features that create opportunities for weighing in new fields and open up new markets.

Developing the AD-1687 Weighing Environment Logger

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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.

When considering the applied voltage of load cells, is the higher the better?

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Customers often ask me, “For the applied voltage of load cells, the higher the better, right?” These customers usually have an understanding of electricity and logically point out that, “If the applied voltage of the load cell is doubled, the output voltage doubles proportionally. This in turn will increase the signal/noise ratio and reduce the variation of the indicator value by half”.

Well, another tricky question, I always think. That’s because when I explain my answer, customers often tell me that they are confused. What the customers are saying is definitely correct in principle. However, there’s a reason why it doesn’t tell the whole story for load cells.

Let’s look at a question about Ohm’s Law.

Q: If 5 V and 10 V are applied to a resistance of 100 Ω, what are the respective power levels?
A: P (power) = V2/R

For 5 V, 5*5/100 = 0.25 W
For 10 V, 10*10/100 = 1 W

We can see that power increases in proportion to the square of the applied voltage.
In other words, doubling the applied voltage quadruples the heat generated.
That’s why all manufacturers regulate the maximum applied voltage of their load cells.
If the applied voltage exceeds this limit, combustion may occur.

Furthermore, temperature increases caused by the dissipated power create a temperature difference between the load cell and ambient air. This causes convection, which is like the steam slowly rising from a hot cup of coffee. The convection causes ripples in the surface temperature of the load cell, which causes the surface material of load cell (aluminum, steel, etc.) to expand and contract. This is detected by the strain gauge and causes the indicator value to fluctuate. What’s more, when a lot of heat is generated, even a small amount of air from outside the instrument may also cause irregularities in the surface temperature of the load cell, which may also cause the indicator value to fluctuate.

So this leads to another difficult question: “So that means the lower the applied voltage of the load cell, the better?” Actually, when the applied voltage of the load cell is small, the output power is lower, which makes the load cell more likely to be affected by disturbances such as ambient noise. This leads to the question, “So, which is it?” Even if the applied voltage is low and the noise ratio increases, it’s OK as long as you use a filter that can eliminate as much noise as possible. This means that even if the applied voltage is halved and the noise ratio is doubled, it’s better to increase the performance of the noise-eliminating filter by 2 times or more.

That’s why A&D lowered the applied voltage to 5 V for the load cells in their new weighing indicators. And lower power consumption is more environmentally friendly, right?

Troubles with hum

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Since their output is so faint, load cells require adequate noise countermeasures such as quality shielded cables or protective tubing. In most cases, the strongest source of noise in the environment around load cells and weighing gauges is power frequency noise, which is generally 50 or 60 Hz. This is known as hum noise.

However, A&D’s weighing indicators have excellent noise elimination properties against this power frequency and are not very affected by it. Strangely, this can be a problem as there are even customers who do not feel the need to use shielded load cell cabling. (Of course, we do not recommend this.)

However, power frequency is not limited to 50 and 60 Hz. The closest one is an inverter. Inverters control the speed of a motor by changing the power frequency, and this generates frequencies other than 50 and 60 Hz. Furthermore, inverters generate various frequencies and voltages through on/off switching at very short intervals when switching between direct current and alternating current, and this switching frequency also generates noise. Therefore, various frequencies, along with strong noise, are often generated in environments in which inverters are used. As mentioned above, the most basic way to counter this noise is through shielded wiring and piping. However, our products that use the High Performance Digital Filter are designed to resist not only sources of vibration such as the floor but also the various frequency noises generated by inverters. We recommend these products to customers worried about noisy environments.

A blown power fuse (Part 2)

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The fuses of devices that have been used for many years sometime suddenly blow and often metal fatigue is the cause. But why would a fuse with no moving parts be affected by metal fatigue? When the power is switched on, the inrush current instantly heats and expands the fuse. Later, the fuse returns to its original condition. This process repeats again and again, which causes wear over the years that may cause the fuse may blow.

Even with the same fuse, high ambient temperatures make a fuse more likely to blow. Higher temperatures lower the resistance value of the fuse, which makes heating and fusing more likely. Because of this characteristic, it is normal practice to select a fuse 1.5 to 3 times the rated current of the device used.

A blown power fuse (Part 1)

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We received an inquiry from a customer about a fuse that blew after they switched from an old to a new weighing indicator. Apparently, the old one was over 20 years old. The power circuit of an indictor that old is likely to be a series type rather than the currently popular switched-mode type.

When you choose a power fuse, you first must consider the power consumption of the device being used. At minimum, you need a fuse for a current capacity that can supply the power consumed. So, how much of a margin is needed for fuses?

Let me ask a tricky question. Imagine you have a 100 V, 60 W incandescent light bulb. When you light the bulb, how much current flows? The calculation would be: 60 W ÷ 100 V = 0.6 A. So, is it OK to use a fuse with a 0.6 A rating? The answer is “No”. Let’s try and measure the resistance value of this incandescent light bulb. A 60 W light bulb that I have on hand has a resistance value of a mere 14 Ω. If 100 V is applied, the current flowing is 7 A, right? If you actually apply 100 V, a large current flows at first but it gradually drops and eventually reaches 0.6 A. Since the filament temperature is low when the power is first switched on, the resistance value also is low, but as the temperature rises, so does the resistance value. Therefore, if the characteristics of the bulb and fuse are mismatched, the fuse blows as soon as the power is switched on. This large current when the power is switched on is called inrush current.

Let’s bring the discussion back to weighing gauges. Because they are low in noise and simple, series-type power sources (power circuits using large power transformers) were used for the power circuits of electrical devices like weighing gauges until the 1980s. These power circuits were inefficient but the inrush current was not so large. However, currently popular switched-mode power supplies have a large inrush current when the power is switched on but this current tends to flow for only a short time. Therefore, changing weighing indicator types, even for one with similar power consumption, makes it likely that the fuse will blow.

So, what can we do about this problem? You must switch to a slow-blow fuse. There are three main types of fuses.
– Fast blow
– Normal blow
– Slow blow

Slow-blow fuses strongly resist the inrush current when the power is switched on and blow like a normal fuse with further overcurrent. These fuses can be identified by the letter “T” before the rated current marking. For example, a 1 A slow-blow fuse would be marked “T1A”.

For reference, the following A&D weighing gauges use switched-mode power supplies: AD-4401, AD-4402, AD-4404, AD-4408A/C, AD-4530, and AD-4532B. (as of May 2011)

Please ground your devices!

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We started an investigation after hearing from a customer in South East Asia. He said that weighing indicators were quickly breaking, even after several replacements, and that one had broke after 2 weeks just recently.

However, the so-called quickly broken indicator was one of our long-selling items and not easily broken. When such cases occur, the cause is often peculiar to the location. However, this site was overseas and not easy for us to visit so we asked the customer to send us a connection diagram.

I soon received an extremely hard-to-read scan of a ragged diagram that looked like it was from some ancient text. What’s more, it was in Japanese. It appeared to be for a scale that had been assembled by a Japanese company around 20 years ago and then exported overseas.

While it was very hard to make out the diagram, I found the notation “Power cord 2P” while zooming in on it. “Power cord 2P” means an AC power connection with only two pins and no ground pin. I thought, “Well, there’s your problem!”

Certainly, a weighting indicator will run without a ground pin and many consumer electronics have a power cable with only two prongs.

However, unlike consumer electronics, weighing indicators have a number of long cables, including the load cell cable, and they are sometimes connected outdoors.

As a result, if an ungrounded indicator receives noise voltage such as a lightning strike or static electricity, the voltage will pass through the electric circuits inside the weighing indicator and damage them.

While many Japanese homes have 2-pin AC outlets, offices and factories commonly have 3-pin outlets with a ground terminal. Unfortunately, most people ignore grounding because they know from experience that devices will work without it.

I urge anyone reading this article who uses a desktop computer to check that it is properly grounded.