Which requirement is essential for a sampling device used in a belt stream?

The requirement that a sampling device must be large and deep enough to handle the stream is crucial because it ensures that the device can adequately capture a representative sample of the aggregate material flowing on the belt. A sampling device that is too small or shallow may not be able to gather enough material or may miss critical components of the aggregate blend, leading to inaccurate sampling results. This principle is especially important in aggregate sampling because obtaining a representative sample is vital for quality control and testing purposes. Proper sampling enables technicians to evaluate the characteristics of the aggregate, such as gradation and moisture content, which are essential for ensuring that the mixture meets the specified standards and performs as intended in construction applications.