Abstract: A signal level crossing detector circuit includes a DC isolator and a detector circuit. The DC isolator has at least a first input, which is operable to receive a high voltage AC signal, and at least a first capacitor, a first plate of the first capacitor being electrically connected to the first input. The detector circuit is operable at a low voltage and has at least a first detector input, the first detector input being electrically connected to a second plate of the first capacitor, the low voltage detector circuit being operable to provide a change in output signal in dependence on a high voltage AC signal on the first input crossing a predetermined signal level. The signal level crossing detector may be single ended or differential.

Abstract: A voltage measurement circuit is operative to measure a high voltage AC signal and includes a capacitive divider circuit and a compensator circuit. The capacitive divider circuit includes first and second inputs, across which, in use, is received a high voltage AC signal and also includes second and third capacitors. First and second plates of each of the first, second and third capacitors are defined by conductive layers of a printed circuit board and the dielectric of each of the first, second and third capacitors being defined by a non-conducting part of the printed circuit board. A compensator circuit has a configurable transfer function and includes an input connected across the first and second plates of the third capacitor and an output. The compensator circuit is operative to change a voltage received at its input in accordance with the transfer function and to provide the changed voltage at its output.

Abstract: Computer cooling equipment for computer equipment comprises: a primary heat transfer circuit; a secondary heat transfer circuit containing a secondary heat transfer fluid, a secondary condenser cooled by the primary heat transfer circuit and a secondary evaporator for cooling the computer equipment; and is characterised in that the secondary heat transfer fluid is a volatile fluid. The secondary heat transfer fluid may be carbon dioxide. The cooling system is of particular use in power hungry applications such as cooling of computer servers, particularly of blade servers as it can produce a heat load dissipation of up to 100 kW, compared to 10 kW or less using conventional systems. Heat exchange cabinets, air conditioning systems and building elements using a secondary heat transfer fluid which is a volatile fluid are also disclosed.

Abstract: A system for cooling electronic equipment, especially modular electronic units mounted in racks, each having a casing with an air inlet, an air outlet and a fan for cooling the contents of the unit. The system uses a chiller unit, between adjacent racks for returning cooled air to ambient, each of which can be a piping array connected to a supply of chilled water. A baffle backing the piping array improves heat exchange and provides a more uniform transfer of heat to each array, thereby enabling optimum temperature differences to be achieved across each rack. A slidable framework supports the piping array and defines an air space on the cooled air side of the array. An auxiliary piping array extends rearwardly of racks so as to communicate with rear air spaces behind the racks and thereby cool heated air flowing in the rear air spaces.