data acquisition I / O moduleData acquisition I / O modules are the cards that provide input and output functionalities within a data acquisition system. As the data acquisition system controls, monitors, and analyzes the processes, it can take different types of inputs from devices including sensors, timers, solid-state circuits, or relays. Thus different types of I / O modules can be added to the DAQ system. Data acquisition I / O module performance, computer bus, and environmental parameters are the important specifications while considering data acquisition I / O modules.

Performance of DAQ I / O Module

The performance of Data acquisition I / O module is based on three parameters. These include digital I/O Channels, differential analogue input channels, and resolution. Digital I / O channels provide low-level on-off signals required for many DAQ applications. User interface, Communication, or controls are applications that use such on-off signals. Differential analogue input channel takes either input as the combination of two single-ended signals or the difference between two signals with filtering out the common mode. Resolution of data acquisition I / O module defines how fine an analogue signal is represented by a digital value. For example an analogue 10 V signal can be represented by 10 bits value in .01 increments (210 = 1024 and .01 X 1000 = 10). Resolution gets doubled with the addition of an additional bit. One sign bit is used to define polarity of the signal. Larger the bits greater will be the fineness or digitization. Also increasing the bits causes other problems such as alias effects.

Data Acquisition I/O module Bus Specifications

Data acquisition I/O modules support both internal and external bus standards. These include PCMCIA standards, Mac PCI (Nubus), ISA, EISA, PCI, Compact PCI, PC 104, PC 104-plus, EBX, Multibus (I &II), MIX bus, IBM Microchannel, PXI bus, PMC bus, PMC bus, SUN Sbus, VXI bus, and VME bus. Serial external connectors include RS232, RS422, RS485, Universal Serial Bus (USB), and FireWire. Parallel external connectors support is available for SCSI, GPIB, HPIB, and ATA. These connectors allow the DAQ I / O modules to attach with other devices such as Ethernet network, modems, Radio devices.

Form Factors Of data acquisition I / O Modules

Data acquisition I / O modules are available in various formats. These include printed circuit boards (PCBs), panel mount, rack mount, chassis mount, slot systems, and, DIN rail. Also they are available as stand alone modules.