The Best Calibration Weights to Buy for Your Bench Scales

The whole purpose of buying a bench scale is to obtain accurate results, right? However, those accurate results don’t come without some work on your part. For consistently exact results over time, it’s crucial to calibrate your bench scales with calibration weights. In this blog, we’ll look at what calibration weights are, why your scales need to be calibrated, how to check if your scales are accurate, how to calibrate your scales, and, finally, which calibration weights are the best choice to use with bench scales.

What Are Calibration Weights?

Calibration weights are individual machined or cast metal that are each carefully crafted to be a particular standard weight, such as 1 kilogram. When placed on a scale during calibration, that 1 kilogram weight will essentially teach the scale what 1 kilogram means, or what it ‘feels like’. The scale will then use this knowledge to compare every item you weigh in the future against that 1 kilogram. For example, if you weighed an item that you knew to be about 0.5 kilograms, the scale would be able to provide this result because it recognizes that the item is half the weight of a kilogram. Of course, many people weigh items much lighter or much heavier than 1 kilogram, which is why calibration weights come in sizes from as small as a single milligram to as large as 50 kilograms.

Because this is such a broad range, there are a variety of materials that your calibration weights can be made from, depending on just how accurate you need your scale to be, such as aluminum, stainless steel, bronze and cast iron. There are also different classes of calibration weights. When calibrating a bench scale, the accuracy doesn’t need to be extreme like it would be if you were calibrating a semi-micro balance, so M1 class calibration weights are perfect.

Why Do My Scales Need to Be Calibrated?

Calibrating your scale is essential to receiving correct weighing results. Without calibrating your scale, you’re at risk of weighing errors that can negatively impact other areas of your work. Calibrating your scale can also help to reduce complaints from customers and business partners, as you are confident weights are correct.

For more information, check out our previous blog, Just How Important is Calibration?

How Do I Check if My Scales Are Accurate?

It’s a good practice to schedule regular check-ups to see if you need to recalibrate your scale. The simplest way to test if your scale is accurate is to place a calibration weight on the pan and check that the result on the display is equal to the calibration weight.

Generally, a scale will be tested through its range from 0 to its highest capacity, adding calibration weights to the pan one at a time, while keeping an eye on the display, until capacity has been reached.  If the numbers are correct, you don’t need to recalibrate your scale. If they’re not, it’s time to move on to the next step.

How Do I Calibrate My Bench Scale?

You should only calibrate your scale if you are qualified to do so. If not, you should find someone who is! All scales will generally work the same when it comes to calibrating, though the instructions may differ from bench scale to bench scale (read your manual!). For simplicities sake, we’ll focus on how to calibrate Adam Equipment’s Aqua ABW-S Waterproof Bench Scale.

1. In normal weighing mode, press the Function button and hold for 3 seconds. Once the display shows “S1 Un”, press the Tare key (some keys may be multi-purpose) to cycle through the menu until you see “S8 CAL”. Press the -->0<-- button. The display should show “UnLoAd”.
2. Press the -->0<-- key again, which will show the last calibration weight with the first digit flashing. To change the value, use the --> and ↑ keys, then press -->0<-- once again to accept. The display will stop flashing.
3. Add the calibration weight that is displayed on the screen to the pan. Wait a moment for it to stabilize, then press the -->0<-- The display will show “PASS” and then return to normal weighing after a few seconds. For the ABW-S, if the results are outside of the previous calibration value by more than 5%, it will display it as a “FAIL” with either an L or H, depending on if it was lower or higher.

That’s it! There’s quite a lot of button-pressing involved, but the time it takes is worth it for better weighing results.  

The Best Calibration Weights for Bench Scales

We’re going to be working on the assumption that those using bench scales have models with a capacity between 6 kilograms and 60 kilograms. In this case, M1 test weights are the best to use. Robert of Inscale recommends, for a 16-kilogram capacity bench scale:

1 x 1kg

2 x 2kg

1 x 5kg

1 x 10kg

This allows the scale to be tested at different intervals up to the capacity. Here are options relevant to a bench scale of this capacity:

Kern’s M1 Class Single Finely Turned Stainless Steel Calibration Test Weights

Kern’s selection of M1 Class calibration weights ranges from 1 gram to 10 kilograms. Each is constructed from cylindrical finely turned stainless steel and complies with OIML R111-2004. The benefit of single calibration weights is that you can only buy the ones that you need, which saves you money!

Kern’s M1 Class Calibration Test Weight Finely Turned Stainless Steel Box Sets

Kern’s M1 Class Calibration Test Weight Box Set is a complete set of calibrated test weights that comply with OIML R111-2004. The lowest capacity model is from 1mg-500mg, while the highest capacity model is from 1g-5kg. The lightest weights are constructed from aluminum and German silver, while the heavier weights are stainless steel. This box set is complete with gloves and tweezers that are perfect for handling the smallest weights.  

Adam Equipment’s OIML Calibration Weights

Each OIML weight is an individual weight that can be used to test or calibrate a product up to the relevant OIML standard. These weights are available in a range of capacities from 1 gram to 2 kilograms and are constructed from stainless steel for long-term stability. This range of weights also has F1 and E2 options, though we recommend using M1 for bench scales!

M1 Class Single Cast Iron Block Calibration Test Weights

For scales with higher capacities, this M1 Class Iron Blog Calibration Test Weight is an excellent choice. Ranging in weight from 5kg to 50kg, these calibration test weights are constructed from solid cast iron, perfect for scales and balances that require less precision!

Once you’ve found your perfect calibration weights, you need to take good care of them so that they stay the weight that they’re meant to represent. To learn more, read our blog The Care and Keeping of Calibration Weights.

If you have any questions about which calibration weight is right for you, contact the Inscale team.