A measurement apparatus may include a holding hopper configured to receive a sample of granular material. The measurement apparatus may include a top barrier assembly coupled between the holding hopper and a sub-sample measurement chamber. The top barrier assembly may include a movable top barrier configured to be moved from a closed position to an open position to direct a sub-sample of granular material to flow from the holding hopper to the sub-sample measurement chamber. The measurement apparatus may include the sub-sample measurement chamber configured to couple to the holding hopper at a docked position to receive the sub-sample of granular material from the holding hopper. The measurement apparatus may include a separator actuator configured to separate the sub-sample measurement chamber from the holding hopper. The measurement apparatus may include one or more measurement sensors configured to measure one or more attributes of the sub-sample of granular material.