backplaneBackplanes are the printed circuit boards containing number of expansion slots or sockets. These sockets offer connections for other circuit boards to the backplane. Backplanes are available in two types. One is active backplane and the other is passive backplane. Active backplane has a simple architecture without processor complex components such as chipset, CPU, or cache. However active backplanes do have bus control and motherboard circuitry. Active backplane may also contain a slot to plug-in CPU. Passive backplane on the other hand are a bit complex with processor complex components, buses, and drivers (interface between hardware and software). One thing that is common in most backplanes is bridge. A bridge provides interface between two different or same types of buses.

Backplane Specifications

Selection of a backplane depends upon its specifications, which include number of expansion cards, number of segments in the card, bus type, form factor, and some extra features.

Backplane Buses

A bus type gives information about the type of slots in the backplane. The Backplanes offer verity of buses including industrial standard architecture (ISA) for I /O devices. Other includes EISA, PCI, CompactPCI, and Versa Module Eurocard (VME) bus. VME is suitable for rough and rugged environments. VME extensions for instrumentation (VXI), embedded PCI extended (ePCI-X), embedded technology extended (ETX), multi system extension interface (MXI), and advanced telecommunication computing architecture (AdvacedTCA) are the industrial backplane standards.

Form Factors for Industrial Backplanes

Industrial backplanes are available in number of form factors and one of them is Advanced Technology (AT). AT supports IBM motherboards for personal computers. AT standard comes in two sizes. One is 12-inche wide with 13.8-inch depth, and the other is 8.57-inch wide with 13.04-inch depth. In other standards there are LPX, ATX, and NLX. ATX contains features of both AT and LPX. NLX form factor support the technologies such as universal serial bus (USB), dual in-line memory module (DIMM), and advanced graphic ports (AGP). Moreover NLX can also work with the current processors and technologies. NLX standard comes in 9-inch wide and 13.6-inch deep form factor. Some other backplanes are categorized according to size. These include 100 mm X 160 mm Size A, 233 mm X 160 mm Size B, 233 mm X 340 mm Size C, 360 mm X 340 mm Size D.

Backplane Testers

Backplane testers measure the integrity of backplanes and record it. They also check whether the passive components such as capacitors, resistors, or diodes are working fine. They can also analyze the open and short circuits situations in the system. In-circuit testing technique and Manufacturing defect analyzers (MDAs) are suitable for analogue testing of backplanes. Backplane testers are available as hand held, floor standing, portable, internal, and external backplane testers.