Data Acquisition

Figure 3.11Two-stage Butterworth filter3.2.4 LinearizationAs we have seen, the output signals from transducers such as thermocouples exhibit anon-linear relationship to the phenomena being measured over a given input range. Thedata acquisition software typically performs linearization of these signals. However,where the non-linear relationship is predictable and repeatable this task can be performedby intelligent signal conditioning hardware. This typically requires the signal conditioningequipment to be programmed for a particular type of transducer, but oncecompleted, the measurements returned to the host PC or stored as part of the measurementprocess are directly related to the phenomena (e.g. temperature) being measured.Signal conditioning products, available from many different equipment manufacturers,are provided in many different forms covering a range of price, performance, modularityand ease of use. The type of signal conditioning hardware should be matched to the specificapplication. The main forms are discussed below.3.3.1 Plug-in board signal conditioningThis range of signal conditioning hardware typically covers specialty plug-in dataacquisition boards where the signal conditioning hardware is contained on the boarditself. This is shown in Figure 3.12.Figure 3.12Plug-in DAQ board signal conditioning