by Laura French, Associate Editor
Every lab needs a scale — whether you need to determine the weight of a biological specimen, precisely measure out a drug component or prepare a standard for a chromatography run, a trusty scale or balance is a fundamental tool in an endless number of industries and applications. When it comes to selecting and buying a new scale or balance, several obvious factors will come to mind; you’ll want to make sure your new scale provides precise and repeatable measurements, has the sensitivity and capacity to weigh your smallest and largest samples and provides the resolution and readability required for your analysis. You’ll also want to know whether your balance can be calibrated automatically or will need to be calibrated by hand.
While weighing instruments date back to ancient times, the technology has developed far beyond basic mechanical apparatuses and has even gone beyond providing extremely precise and accurate measurements. New quality control features, computer connectivity and the incorporation of automation have transformed scales and balances into advanced machines that fit right into state-of-the-art modern labs. So, while precision, accuracy, readability and sensitivity are of utmost importance, don’t stop there when shopping for a new unit. Explore additional functions and features for the efficiency and productivity you expect from all your laboratory equipment.
Look for features that offer protection from interference, damage and safety hazards
A balance that is sensitive enough to provide microgram-scale precision will also be very sensitive to external contaminants and interference. For this reason, draft shields to keep out dust and air currents, as well as controls to manage fluctuating temperatures, have become standard features in the analytical scales market. Static and external vibrations are two other influences that can lead to inaccurate readings and add time to the weighing process if measurements need to be redone. Many scales are now made with these factors in mind and are compatible with accessories that target common sources of interference— some models even have protections built into the device.
Static: Some scales come equipped with static sensors and ionizers to detect and remove static without the need for additional anti-static equipment. Ionizers may be built into a draft shield, and shields and weighing pans made from anti-static materials are also available to further protect against this interference.
Vibrations: Vibrations are traditionally mitigated with the use of vibration-damping tables or platforms to physically suppress external vibrations, but vibration-resistance can also be built into the balance design, and digital balances can have the ability to filter measurements for detected vibration interference.
In addition to ensuring measurements are as accurate as possible, you’ll also want to have additional protections that will extend your new instrument’s lifespan— and your own!
Over-loading and shock protection: Too much weight on your electronic scale can damage the loading cell, leading to costly replacements and repairs; fortunately, many scales have over-loading protection that allows the cell to resist damage even when loaded with more weight than its normal operating capacity. This feature means you don’t have to worry about destroying your scale by accidentally pouring more sample on it than you meant to. To protect against more extreme mishaps, like dropping something onto the scale or dropping the scale itself, look for scales with impact or shock protection/absorption. Some scales are even integrated with a shock detection system that alerts the user to inadvertent shock loading.
Corrosion protection: Corrosion is another major threat to your scale’s lifespan, especially if you’re working regularly with harsh chemicals. You’ll want to use scales made from chemically resistant materials like stainless steel and acrylonitrile butadiene styrene (ABS) plastic, which is also static resistant, and you’ll also want to make sure your scale is easy to clean.
User safety: The same hazardous materials that can cause damage to your scale can also damage your health, which is why user safety features should also be considered when picking out a scale. Any automatic features that reduce direct contact with the sample and instrument will reduce the risk of exposure to hazardous chemicals. Terminals with touchless proximity sensor controls can further reduce direct contact, and if the terminal has a touch screen, ensuring the screen can be used with gloves is key when working with harsh chemicals. Ventilated balance enclosures should also be used when working with hazardous substances, although these are typically sold separately.
Products to consider:
- XPR226DR Balance from Mettler-Toledo GmbH
- Cubis® II Premium Laboratory Balance from Sartorius Lab Instruments GmbH & Co.KG
- PowderSafe Type C Balance Enclosure from AirClean Systems
Connectivity and compatible software can boost efficiency and data integrity
Laboratories have become increasingly computerized and connected, and scales and balances are no exception. Ensuring your new balance can be integrated with your laboratory information management system (LIMS) and “communicate” with the other instruments along your workflow will not only save time by removing the need to manually input data, but will also ensure data is accurately recorded, securely stored and traceable for improved compliance and quality assurance.
If you’re looking to take your weighing instruments to the next level with connectivity, there are several things you’ll want to consider. Firstly, you’ll want to check that the balance you choose can be integrated into your LIMS, electronic laboratory notebook (ELN) or analytical software so that it can be easily incorporated into your connected lab. If not, you should weigh the costs and benefits of any additional software needed to facilitate this integration.
You’ll also want to pay attention to the available connection interfaces that will link your balance to the computer, internet and peripheral devices such as barcode scanners and printers. For example, consider how many accessories you would want to connect and ensure there are enough USB ports to accommodate your needs. RS-232 ports enable fast data transfer between computer systems and instruments, and ethernet ports will allow your balance to connect to your lab’s local area network (LAN). Choosing a scale with the interfaces you need will save you the trouble of needing a converter if you decide to connect later.
Products to consider:
- AT-R Series Analytical Balances from Shimadzu
- Precisa Series 520 PB 3200C SCS Precision Balance from Techcomp
- LabX Laboratory Software from Mettler-Toledo GmbH
Additional “bells and whistles” turn weighing instruments into multifunctional smart scales
Although scales and balances have been serving the same basic purpose of measuring mass for thousands of years, centuries of development have only improved the efficiency and performance of this function, including the addition of other features that complement the weighing process. One of the most useful add-ons that can turn a basic scale into a smart scale is automation, and there are a range of different processes that can be automated when it comes to weighing.
One example is automated calibration; international automatic calibration can save scientists significant time by calibrating the instrument at set time intervals or in response to environmental factors like temperature. Draft shield doors that close and open automatically are another basic example. A more advanced example of automated weighing is the addition of automated sample dispensers; these dispensers can be programmed to dispense a precise amount and concentration of sample and solvent for accurate, hands-off weighing and sample prep for downstream applications such as HPLC. Dispensers can further be equipped with autosamplers to measure out a precise weight into several vials all in one run. Automated features are expectedly more costly, so consider what the return on investment may be in terms of your lab’s throughput and efficiency.
Another advancement in weighing technology that has become much more common is the inclusion of digital terminals with multiple controls that improve ease of use and offer additional options and modes to choose from. Terminals may use traditional buttons or keys, or they may have a touch screen and touchless IR proximity sensors. A highly visual and customizable touch screen display will be helpful if your scale is connected to a computer system, although some scales can also be remotely controlled through a computer or mobile device. Touchless controls placed alongside other controls may be programmed with quick commands to activate basic functions like taring with a simple hand motion.
The digitalization of scales and balances has also allowed for more built-in functions, even when the instrument isn’t connected to a computer system. For example, many scales are able to both weigh and count pieces, combining two instruments into one. Other modes and settings a digital scale may include are dynamic weighing, for unstable liquids or live animals, accumulative weighing, to get the total weight of several smaller samples without overloading the scale, and percentage weighing, which will tell you what percentage of a larger reference weight one component will make up. If you need to convert units, for example, if you need to convert grams to ounces, many digital scales can easily do this as well.
Take into account the different weighing modes and features a scale or balance offers when considering the best one for your lab; a pharmaceutical lab may find piece counting and percentage weighing especially useful for measuring tablets and drug components, while a vivarium will likely need dynamic weighing to monitor scampering insects and rodents, and a food lab may find built-in unit conversion helpful to ensure the accuracy of labels that display both grams and ounces.
Products to consider:
- XPR Analytical Balances from Mettler-Toledo GmbH
- LeDoser Automatic Weigher and Flux Dispenser from Malvern Panalytical
- CCR Table Top Mass Comparator from Sartorius Lab Instruments GmbH & Co.KG
When shopping for scales, it may be helpful to start with a checklist of the features and functions you want or need, and then decide how many items you want your scale to have built-in, and how many you may want to acquire separately. See how many boxes each option checks off, weigh the costs and benefits of each instrument and any supplemental equipment, and make the best decision for your laboratory, your budget and your scientists.