Strict guidelines define exactly how samples are taken and how much bad grain in a container is enough to condemn the entire container. Grain is sampled often and according to well defined rules. The grain elevator operator stays informed about the quality of grain brought to the elevator by truck or rail and checks the grain again during the blending process using automated samplers. Probe samplers are allowed for use on trucks and railroad cars. The depth of the carrier or container dictates the length of probe used to draw the sample.
Probes consist of two tubes, one inside the other.
The inner tube is divided into compartments. The outer tube has slots which match the compartment openings of the inner tube. When the slots are aligned, grain can enter into and be emptied from the compartments. This activity will use plastic drinking straws instead of metal to construct model probes for testing sample containers of rice or other small grains. Teacher should construct at least one sample probe to show the students and to determine the optimum size of the sampling window.