Abstract: A fluid sampling device including a manifold having inputs, common purge and sampling pathways, valves disposed to couple and decouple a first set of the inputs to the common purge pathway and a second set of the inputs to the common sampling pathway, and a differential sensor coupled to the pathways. A controller connected to the valves produces control signals that enable the valves to couple and decouple the inputs to the common sensor and purge pathways. In addition, a method for operating a fluid sampling system that is connected to a set of sample zones that includes the steps of sampling fluid from first and second sample zones in respective first and second sample locations, isolating third and fourth sample zones from the first and second sample locations, and measuring a differential parameter across the sample locations.