The researchers have developed a method capable of measuring the moisture content of agricultural products within one second using an electromagnetic wave. An object can be measured regardless of its size or shape, and even if it is packed or boxed.

Principle of moisture content measurement using a microstrip transmission line

Moisture content is measured utilizing the fact that when bringing the object being measured close to a microstrip transmission line, the electromagnetic field distribution (amplitude and phase) changes.

The moisture content of agricultural products is an important index of quality. However, conventional methods are problematic in terms of time and effort of sampling and measurement. In the developed method, agricultural products on a conveyer belt are irradiated ten times using an electromagnetic wave with a frequency of several GHz and signal analysis of the transmitted wave is then performed. Since the data is acquired within one second, all products can be inspected in close to real time. Agricultural products can also be measured after being boxed, and therefore this method is expected to facilitate sorting and quality control at the production site.

The moisture content of agricultural products is determined by extracting a sample from a large amount of agricultural products in a place such as a collection point, and measuring the electrical resistance of a ground product or measuring the difference in weight before and after drying. However, sampling and measurement require time and effort. For this reason, there has been an increased need to develop a method capable of performing quality inspections in a short period of time of all agricultural products to be shipped, and further inspecting the final packed products.

The developed technique allows the inspection of the internal state of the object by detecting slight changes in electromagnetic field distribution, and therefore can be applied to such tasks as measuring the sugar content of agricultural products or inspecting foreign substances mixed in food. In the future, the researchers will investigate such applications.