Laboratories

Laboratories in schools , universities and industrial establishments often need special services which are not required in other areas. The most common electrical service of this kind is an extra low voltage supply . This is usually obtained from a stabilised supply  unit which is plugged into the bench mains sockets , the socket being installed on angled bench trunking . For higher current applications , a transformer from the mains , which can either provide a fixed secondary voltage or be of the tap-changing type to give a choice of voltages , or even a variable voltage transformer , may provide the supply . A rectifier is often incorporated so that an extra low voltage a.c supply . Laboratory benches supplied through angled bench trunking , as shwon in Figure 1.20 , are provided with special terminals to connect equipment to the laboratory supplies which must be shrounded so that there are no live conductors exposed to touch as the laboratory equipment is being connected .