Laboratory balances come in a few different shapes and sizes, each with their own advantages and disadvantages. Since they're highly specialised equipment, it's important to know the distinctions between semi-micro, analytical, precision, and top-loading balances. This blog post will do just that, using our Equinox, Solis and Luna balances as examples.
What is a Semi-Micro Balance?
While semi-micro balances are often confused with analytical balances, they are not exactly the same. Semi-micro balances are even more accurate and precise than analytical balances. They derive their name from their ability weigh a mass as fine as 0.01mg/ 0.1mg (10µg/100µg). They can remain very precise in quantities measuring milligrams. A true microbalance can measure in micrograms, while a semi-micro weighs in grams and up to 10 micrograms.
Semi-micro balances are usually dual range balances, meaning that they can weigh in smaller increments at the lower end of their capacity, then in larger increments with the more you weigh. They automatically weigh samples at the best readability available, depending on the mass of the sample. For example, if you have a beaker that weighs 100g, you can tare that and still weigh your sample in increments of 0.01mg.
Semi-micro balances are frequently used to weigh powders, drugs and chemicals in small increments, often in laboratories with high tolerances. They're usually paired with an anti-vibration table because of their acute sensitivity. That high level of accuracy is an advantage for highly detailed testing in research laboratories. They also offer complex, yet intuitive features designed to simplify difficult weighing tasks, especially in chemistry and pharmacological laboratories. Semi-micro balances also offer the precision necessary for differential weighing and pipette calibration.
The disadvantages of using a semi-micro balance are its high price tag and the same sensitivity that makes them so useful. They can pick up on the slightest changes in mass brought by temperature or static electricity, so it's imperative to use them in areas built to reduce environmental interferences to measure the actual mass fluctuations. Many laboratories place them under hoods or enclosures to ensure precise results. They feature a low capacity, but they're designed to weigh minute samples, so their high readability compensates.
Our own semi-micro balances include the Solis and Equinox ranges, with capacities ranging from 62g / 120g to 82g / 220g and readabilities of 0.01mg/ 0.1mg.
What is an Analytical Balance?
While analytical balances are slightly less precise than semi-micro balances (their readability tends to be around 0.0001g), they are usually used with an anti-vibration table to help minimise mass fluctuations caused by their environment. They're still very precise and pick up on slight changes, so precautions must be taken to accurately measure small samples. These types of balances are one of the most commonly used tools in a laboratory, from life sciences to forensics. Analytical balances are frequently used for quantitative analysis and reagent measurement in chemistry.
Analytical and semi-micro balances both feature draught shields that enclose a small weighing chamber designed to protect the sample from environmental factors like drafts or static electricity. They tend to share features such as formulation or percentage weighing.
What is a Precision Balance?
While their readability is not as fine as analytical balances (ours go to 0.001g), precision balances are sturdier and feature a higher capacity (from 220g to 2100g), so they can weigh heavier samples. They're frequently used to measure materials to obtain samples that will then be weighed and processed on balances with finer readabilities. In a laboratory, a precision balance is often the first step for weighing and processing samples, as well as for quality control. They can also be used in medical fields where samples like blood bags are heavier but still need to be measured with fine readability.
What is a Top-Loading Balance?
Much like semi-micro and analytical balances, precision and top-loading balances are often confused because they are quite similar. It's also not uncommon for some of their functions, capacities and readabilities to overlap. However, there are a few key differences. As their name indicates, samples are weighed by placing them on top of the top-loading balance's weighing pan, rather than placed in a weighing chamber. They feature no draught shield and usually have a much larger weighing pan, often square or rectangular.
Top-loading balances feature high capacities (ours range from 2600g all the way to 15000g) and robust housing. They are much less precise and accurate than analytical balances, with readabilities ranging between 0.01g and 0.1g.
Top-loading balances are well-suited for larger, messier samples that are raw or need to be processed. They're frequently used for material testing applications in construction and engineering where precision is still needed, but the balance cannot be as sensitive to minute changes because they are used in more demanding environments.
Top-loading balances are also very useful for applications where density is important, since they offer a large capacity with smart features that can do a lot of the work for the user.
They're also well-suited for mobile laboratories where the conditions are less than ideal, and the samples are larger. Because they can weigh larger batches, top-loading balances are often used for pilot production or small batch production.
Some precision and top-loading balances offer compact options with fewer functionalities but comparable readability and capacity (like the Core or the Highland). If you need a basic precision balance without a graphical display or complex functions, compact precision balances offer models with or without draught shields and high accuracy. You can still perform tasks like percentage weighing or accumulation with the Highland while the Core offers basic weighing only. They can be cheaper and offer battery-powered operation, so they can be transported if needed.
Features Common to Semi-Micro, Analytical and Precision Balances
They might not be built for the same things, but they are all laboratory balances, which means they include a few essential features, no matter their capacity or pan size.
Both analytical and semi-micro balances offer draught shields. Some types of precision balances with higher visibility offer draught shields as well. It's not uncommon for product types in the same range to share features like density weighing or percentage counting as well.
No matter the capacity or readability, a laboratory balance should be able to connect to printers and computer systems. Adam balances usually connect to peripherals via RS-232 interfaces. Our Luna even includes a USB interface for easy connection.
Most laboratory balances also feature a bright graphic display to show information and symbols helpful for navigation. Some of them even feature touch screens. All these types of balances include external and internal calibration models, so you can pick the best option for your needs.
Most semi-micro, analytical, precision and top-loading balances need to be plugged in to function.
While there is some overlap, semi-micro, analytical, precision and top-loading balances all have their uses in laboratories for various tasks. Knowing which tool is best adapted to a task can help you save some time and money.
Still trying to figure out which balance works best for your laboratory? Contact us, we'll be happy to help you.