What is a Weigh-Below Hook Used For?

Some bench scales and laboratory balances have the versatility for below balance weighing with the help of a weigh-below hook. This blog will discuss what a weigh-below hook is as well as the benefits of using one.

What is a Weigh-Below Hook?

A weigh-below hook is a tool that attaches to the load cell of your scale or balance through the bottom. This gives your scale the capability to display the weight of any item hung on the hook, like a hanging balance. To employ a weigh-below hook, you’ll need a way to expose the bottom of your scale. This is  so the item can hang freely and unobstructed from the hook. You'll also require a hanging method for the item, such as a bag or another handled container that you can tare for accurate results.

Benefits of a Weigh-Below Hook

A weigh-below hook can be useful for a variety of reasons that would prevent you from weighing on the pan:

Large or Abnormally Shaped Samples

Though an item may be below your scale or balance’s capacity in terms of weight, the size of your sample could impact how accurate your results are. For example, if you’re attempting to weigh a watermelon with a precision balance. Though it may technically be under the capacity, it may be too large to fit on the pan itself. Placing the watermelon in a bag and suspending it from a weigh-below hook will give you the accurate results you need without worrying about the size or shape of the watermelon.

The watermelon can also be difficult because of its abnormal shape – perhaps it keeps rolling off! Weighing abnormally shaped samples below the balance works better, especially when the sample has an irregular center of gravity with one portion significantly heavier than another, or when it cannot lay completely flat. The weight distribution can disrupt weighing results and make them less accurate. 

Liquid or Messy Samples

If you frequently deal with wet, messy samples, we always recommend using a washdown scale, since they offer an IP rating and won’t be damaged by water or dirt ingress. However, if liquid or messy samples aren’t the norm, there’s no need to purchase a specialised scale. Instead, a weigh-below hook prevents the danger of damage caused by spills.

Samples with Extreme Temperatures

The metal of a weighing pan and load cell can be susceptible to expansion and contraction when they encounter extreme heat or cold. If you’re weighing anything like molten glass or ice sculptures, we recommend using a weigh-below hook to spare your scale.

Density Determination

One way to determine density is by suspending the item with unknown density from the weigh below hook. Record its initial weight, then submerge it while still suspended into a liquid of known density. Record the weight change and use it to calculate the density of your sample. This is a fairly simple process, but without a weigh-below hook, it’s much more difficult.

Tension or Force Measurements

Particularly in the materials testing industry, weigh-below hooks can be utilised for measuring tension or force. For example, let’s say you’re working to create an industrial strength rubber band. You would need to know how much weight the rubber band can handle before it stretches too far and breaks. To test this, you might hang a clamp that’s holding the rubber band onto the weigh-below hook and slowly hang weights from the rubber band to apply more force. The scale will measure the cumulative total of those weights, providing you with precise information about when the band's integrity becomes compromised enough to render it useless. If this amount of weight isn’t as much as you were hoping for, this gives you a hint to get back to the drawing board and consider a different formula.

Calibration

If you find yourself below-balance weighing often, you may choose to calibrate your balance this way as well. Instead of placing the calibration weights on top of the pan, you would suspend them from the weigh-below hook. We offer M1 Class calibration weights ranging from 1g to 10kg that feature hooks specifically intended for suspension use. Please keep in mind that M1 Class calibration weights are not intended to calibrate highly precise analytical balances.

Need help finding a scale or balance with below balance weighing capabilities? Contact the Inscale team.