How Do Hay Moisture Testers Work?

A farmer goes out to the barn with a moisture tester in hand. He chooses a bale, inserts the probe, and pushes a button. Almost instantly a number appears on the moisture tester’s LCD screen. The farmer knows right away whether the moisture level in his hay is acceptable or not.

That’s all well and good, but how does it work? How can a single probe measure the amount of water in a bale of hay? If you have ever wanted to know how moisture testers work, this blog post is your answer. Here we explain the basic principles of testing all sorts of grasses and grains for moisture content.

Moisture Content and Density

The first thing to know is that measuring moisture content relies on the principle of density. It is not like bales of hay are dripping with so much water that it can be collected and measured in a beaker. The moisture content is so low that you cannot see it. In some cases, you can’t even feel it. Therefore, measuring moisture relies on measuring the density of the product.

The more water in a bale of hay, the denser that bale is. The opposite is also true. So hay moisture testers are not really looking for water they can measure. They are simply measuring density. Moisture content can be extrapolated from that density measurement.

The tricky part about this is that different grains and grasses have different natural densities. This is why a moisture tester designed for hay isn’t appropriate for grains or coffee. It is why you cannot chop up a small amount of hay and effectively test it using a grain tester. You have to use a tester appropriate to the product you’re trying to measure.

Measuring Product Density

So, how does a moisture tester actually measure density? By sending electrical current throughout the product and then measuring it when it comes back. Bear in mind that water conducts electricity very nicely. So does air, but not nearly as well as water.

The probe typical of a hay moisture tester actually consists of two components. One discharges the electrical current while the other receives it. This creates a complete circuit that can be measured by the tester’s internal components. The amount of resistance in that circuit determines the density of the product.

A bale of hay with a higher moisture content will present less resistance due to the conductive properties of water. The dryer bale will present more resistance. That’s really all there is to it. Moisture content is extrapolated based on density, and density is measured according to the amount of electrical resistance in the hay.

Multiple Readings for Accuracy

While all of this may sound very scientific, note that readings vary based on how loosely baled the hay is. Accounting for such variations is a matter of taking multiple readings. That’s why you’ll see a farmer test multiple locations of a single bale, then test multiple bales in the stack. The idea is to get numerous readings that can be averaged together.

Even after all those measurements have been taken, a grower’s intuition plays a big role in understanding moisture content. Even the most accurate readings may not necessarily tell the whole truth. So farmers rely on a combination of measurements and their own knowledge and experience.

Now you know how moisture testers work. If you need a new tester for hay, grain, or coffee, we hope you will consider what Mytee Products has to offer. Our range of moisture tester products includes a number of different choices at competitive prices.

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