With so many scale distributors and manufacturers, it can be hard to find a reliable laboratory balance manufacturer. Because the measurements that labs take are often extremely sensitive, itÕs important to find a manufacturer that can provide the high resolution, high precision instruments required by a respected laboratory.
Arlyn Scales is a New York-based scale manufacturer with a custom weighing solution for laboratories. Since the release of our Ultra Precision line of scales, purchasing managers no longer have to weigh the pros and cons of choosing a standard industrial scale or a magnetic force restoration (MFR) scale. The first option forces you to sacrifice the resolution of your scale while the second forces you to spend disproportionate amounts of your budget on your equipment.
Understanding the advantages of our ultra precision scales only comes with an understanding of the drawbacks of industrial scales and force motor scales.
Why Industrial Scales Don’t Make Good Laboratory Balances
Industrial scales typically use strain gage load cells, whose accuracy is fairly good and is typically adequate for most industrial uses. However, strain gage load cells simply arenÕt capable of providing high-resolution measurements, especially at higher capacities.
The load cell is an internal component of these scales. Essentially, it is comprised of a metal piece, called a spring element, that is attached to the floor of the scale and the underside of the platform. Any weight applied to the platform is transferred to the load cell, which causes the spring element to bend.
Bonded to the flexures of this spring element are strain gage transducers, which are wired together to form a WheatstoneÕs bridge. When the spring element bends, the flexures also bend, thereby stretching the strain gages, which changes the resistance of the gages and the voltage output of the bridge. This output is sent through an analog-to-digital converter and the digital signal is passed to the scale indicator, where you can read the numerical value that corresponds to the weight on the platform.
To take an accurate measurement, the spring element is required to bend relatively far. So while the strain gage load cell can handle extremely high capacities (up to 20,000 pounds!) it is not sensitive enough to provide high resolution measurements. The higher the capacity of the scale, the lower its resolution. Ultimately, these scales have an average display readability of one part in five thousand, which is not nearly high enough for the sensitive nature of most laboratory experiments.
For example, an industrial bench scale with a ten pound capacity can only provide accurate measurements to two ten-thousandths of a pound (0.002 lb). An industrial scale with a hundred pound capacity can only provide accurate measurements up to two hundredths of a pound (.02 lb) or one hundredth of a pound (.01 lb) at best.
Magnetic Force Restoration Scales Have Their Limits, Too
While magnetic force restoration scales are a viable solution for some labs, theyÕre not suitable for research and experiments done with larger loads. These types of scales generally cap out at a twelve-pound capacity. The largest practical capacity could possibly be as high as fifty pounds.
Because these scales use an electromagnet to oppose the weight of an object, they are sensitive to drifts in temperature, air currents, and vibrations. And while theyÕre expensive to purchase, they can also be delicate and prone to damage. As the weight of the item on the platform increases, so does the amount of electrical current required to counteract it.
The price and maximum capacities of these scales make them impractical for most labs.
Arlyn’s Ultra Precision Line of Scales is the Best Solution
Featuring SAW (surface acoustic wave) driven load cells, these scales address all of the design vulnerabilities presented by industrial and force motor scales. While they feature the same basic load cell/spring element design as the industrial scale, the overall implementation is completely different.
Instead of strain gages, these scales feature two SAW transducers, which are attached to opposing ends of the spring element. One acts as a transmitter while the other acts as a receiver. The transmitter sends a bulk wave that is picked up by the receiver, passed through an amplifier, and back to the transmitter where the process beings anew.
The frequency of this wave corresponds exactly to the distance between the transducers. While the distance is a specific value when the scale is at rest, it changes in response to the weight placed on the platform. By measuring this frequency, weÕre able to determine the exact weight of anything that is placed on the platform. Because there is no analog-to-digital signal conversion, these scales are inherently more accurate than any strain gage scale.
Unlike strain gage scales, which have a readability of one part in five thousand, our ultra precision scales have a readability of one part in one hundred thousand and higher Ð a resolution that is twenty times higher than that of a strain gage scale.
Compared to the .01 resolution of a hundred pound capacity industrial scale, an ultra precision scale of the same capacity has a resolution of .001 pounds.
Because the SAW load cell requires far less flexibility from the spring element, these scales have a maximum capacity of five hundred pounds with a resolution of .005 pounds, compared to the .1 pound accuracy of its strain gage equivalent.
A ten pound ultra precision scale has a resolution of .0001 pounds Ð which is much finer than the .002 pound resolution found on its strain gage equivalent.
Our Ultra Precision Scales are also priced similarly to what youÕd pay for a high end strain gage scale, which is about two thirds less than the initial purchase price of an MFR scale.
Experiment with an Ultra Precision Scale of Your Own
If youÕre still unsure that our ultra precision scales are the right solution, our support staff is standing by to answer any questions you may have. WeÕre also here to help walk you through the selection process and give you advice about your best options so youÕre sure to get the scale that best meets your needs.
