Master terminal unit

The central computer is called the master terminal unit, or MTU. The MTU has two main functions to periodically obtain data from RTUs/PLCs and to control remote devices through the operator station. The operator interfaces with the MTU using software called human machine interface (HMI). The remote computer is called the program logic controller (PLC) or remote terminal unit (RTU). The RTU activates a relay (or switch) that turns mechanical equipment on and off. The RTU also collects data from sensors. Sensors perform measurement, and actuators perform control. 

Master Terminal Units (MTU) collect sensor data from several RTUs and provides the data to other high-level stations (e.g., hmnan machine interfaces (HMI) to give human users a system overview). MTUs also send actuator commands to the appropriate RTU which executes them. 

Figure 9.14. Brillouin spectrometer using fibre optics to increase the signal-to-noise ratio. (1) Light source consisting of a master laser (1a) a slave with matched frequency (1b) and control unit (1c) for sensitive stabilization of the difference frequency Sv. (2) Signal splitter. (3) Fibre coupler. (4) Polarizer. (5) Chopper. (6) Lens. (7) Cuvette placed on a goniometer. (8) Termination. (9) Slit. (10) Broad-band (10 GHz) APD. (11) Photodiode with a smaller bandwidth (1 GHz). (12) Spectrum analyser (10 GHz) for controlling the intermediate frequency Sv. (13) Spectrum analyser (1 GHz) for the measurement of the half-power bandwidth, Av, of the Brillouin peak. (14) Amplifier system. (15) Process control computer. (Reproduced with permission of Elsevier, Ref [96].)...

Figure 7(d) shows that stress relaxation is less sensitive to the model details. Indeed, all curves collapse onto a master curve, providing that the stress is multiplied by N and plotted against i/tr. In these units, the terminal behavior is well described by exp(-2tliR) as given by eqn [31]. More details can be noticed if this plot is multiplied by Vt/ra as shown in Figure 9. In particular, one can see deviations below the Rouse curve for the semiflexible model and deviations upward for the multichain models. As was demonstrated in Reference 4, the later deviations are due to glassy modes, resulting from collisions with other chains. They strongly depend on density and eventually diverge near the glass transition density.

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