An apparatus monitors performance of a power inverter to detect malfunctions. In another embodiment, detecting a signal in an energy channel may further comprise detecting photons scattered from the target sample. Embedded in the metal material constituting the valve body is an axially extended hollow member, belonging to the anti-freezing arrangement, for the passage of a thermovector fluid, the hollow member having respective ends accessible from outside the valve body, for connection to a circuit of the thermovector fluid.