An apparatus for controlling the temperature of an electronic device under test
includes a thermal head having a temperature controlled surface for making thermal
contact with the electronic device. The thermal head defines a flow channel for
passage of a refrigerant fluid so as to cause transfer of thermal energy between
the electronic device and the thermal head. A refrigeration system is connected
in fluid communication with the flow channel of the thermal head to supply refrigerant
fluid thereto. The refrigeration system includes a metering valve operative to
regulate introduction of the refrigerant fluid into the thermal head. A controller
is operative to control the metering valve for maintaining a predetermined temperature
at the temperature controlled surface.