A disposable electrochemical test sensor designed to facilitate sampling of fluid samples. It has a fluid chamber having a novel extra wide sampling entrance, but no additional air escape vent. The chamber provides a reservoir from which a sample fluid can be drawn into the chamber through capillary action. The sampling entrance provided can draw fluid into the chamber through any part of the opening, allowing easy targeting the samples with small volume, picking up smeared samples, and added tolerance to users who jam the tip of the sensor into users' finger. The sampling entrance also serves as air escape vent. Such one opening sensor alleviates over-flow issue often encountered in convenient sensors.