What instrument is used to measure the moisture content of soil?

The correct answer is a moisture meter, which is specifically designed to measure the moisture content in soil. This instrument utilizes electrical resistance or capacitance principles to provide an accurate reading of moisture levels. Moisture meters are essential tools for soil testing in construction and horticulture as they help determine if the soil has adequate moisture for plant growth or for the appropriate compaction before construction activities.

In contrast, while a hydrometer measures the specific gravity of liquids and can be used in soil tests to assess sedimentation rates or particle size distribution, it is not meant for direct moisture content measurement in soil. A compaction gauge is used to determine the density of compacted soil, ensuring it meets required specifications but does not measure moisture content. Similarly, a shear vane assesses the strength of cohesive soils but does not evaluate moisture levels. Each of these instruments serves distinct purposes within soil testing, reinforcing the importance of using the correct tool for the specific measurements needed in construction materials testing.