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Sensors are wired using Category 5 or 6 Ethernet cable using the analog wiring standard shown in Table 1. Two wires are used to carry the sensor output voltage designated as S- and S+. Five wires are used for different voltage power supplies, and one wire is used for the power supply ground. It is convenient if student laboratories are hardwired with data acquisition ports at workstations, but this is not required for use of the Process Control software. When used, each data acquisition port is wired with up to five different power supplies. Sensors are wired to connect to the power supply that they require. Thus, the sensor is powered and monitored through a single port. This scheme is used for a variety of sensors including pressure, strain gage, pH, dissolved oxygen, turbidity, and temperature. For several of the sensors the power supplies are also used to power a signal conditioning circuit to transform the sensor output into a voltage that can easily be monitored with a data acquisition system.
Sensors, Signal Conditioning, and Calibration
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