I/O Modules, Cards and Boards

I/O modules, I/O cards and I/O boards accept data (input) from computers, sensors, transducers, or programmable logic controllers (PLC) and then distribute the data (output) to other devices in the system. Some I/O cards can perform simple computations on the input data before distribution; however, most devices distribute the data without processing. An I/O module varies in terms of the number of input channels and the number of output channels. I/O modules can have a large number of both. Many I/O modules are used for data acquisition in conjunction with personal computers (PC) and other computer processors or systems. Some I/O modules combine the functions of multiple I/O boards on a single I/O card. With these products, a single I/O card can perform four functions: analog output, analog input, digital output, and digital input. These versatile I/O modules, cards and boards are an integral part of data acquisition.

There are several basic types of I/O modules, I/O cards and I/O boards. Examples include analog I/O cards, digital I/O cards, and PCI I/O cards. An analog I/O card can be used under conditions which represent not just an on-state or an off-state, but a current state. Such current state conditions are involved in controlling valves, lights, and frequency inverters. A digital I/O card is a data acquisition board that provides both digital inputs and digital outputs. Typically, these boards use standard logic-level digital signals. Digital I/O cards can have 4, 8, 16 or 32 lines or channels of digital I/O, and can use many combinations of input and output channels. PCI I/O cards enable additional connectivity to serial and parallel devices. A PCI I/O card adds one standard, 25-pin ECP/EPP/SPP parallel port or two standard, 9-pin serial ports via onboard headers. Backplane adapters are included. Plugging a PCI I/O card into any available PCI slot creates an additional parallel port for printers, scanners, or other electronic devices that use parallel communications. In this way, I/O modules, cards, and boards provide the flexibility to use older equipment.

There are many different applications for I/O modules, I/O cards, and I/O boards. For example, an analog I/O card can be used to measure water pressure from a pump, or to monitor temperature in a wood drying kiln. Digital I/O cards are also used for a variety of purposes. Many types of complex signals are measured with I/O modules, cards, and boards.

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