A four particle velocity sensor device

A thermoelectric cooling apparatus includes a plurality of thermoelectric coolers each having a hot side and a cold side. The cold sides of the thermoelectric coolers are arranged to cool an object. The hot sides of the thermoelectric coolers are provided with a heat sink. The heat sink may include a eutectic material which maintains the hot sides of the thermoelectric coolers at a low temperature so that the cold sides of the thermoelectric coolers are able to maintain the object at a cold temperature. The heat sink may have fins for rejecting heat, and air moving means for moving air over the fins to aid in the rejection of heat from the hot sides of the thermoelectric coolers. The fins may be cooled by the eutectic material.