Multiple Input Data Acquisition System

Computer input signals, whether analog or on-off, are the means of inputting data to the computer. For a two-wire system, shown in Figure 10-11, an instrument such as a differential transmitter furnishes DC voltage to power the sensor. However, if the computer input data acquisition system is remotely located in relationship to the instrument panel, multiple system ground faults can occur. 

Low-level input sensors such as thermocouples, turbine meters, speed transmitters and a number of process analyzers complicate system selection. Signal conditioning equipment is required for low-level inputs to both the back-up system and computer data acquisition systems. If the system is to be installed as an intrinsically safe system, multiple grounding requirements conforming to intrinsic safety grounding must be referenced to the same safety ground to avoid multiple ground problems. 

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