Abstract: A refrigerated automatic fluid sampling apparatus having a compressor assembly mounted in an upper portion thereof, above the thermally-controlled sample compartment. The apparatus includes a thermal control system which prolongs compressor life and optimizes compressor operation by exercising the compressor assembly during prolonged periods of non-use, preventing short-cycling of the compressor, and accurately monitoring sample temperatures to minimize compressor starts. The invention further includes a sampling control system which employs a statistical regression model to simulate real-life pumping system and operating characteristics so as to accurately deliver a predetermined sample volume, which permits sampling on a constant time, variable volume basis as well as other sampling modes.