Dual output temperature controllers

The heart of the system is a microreactor packaging scheme that is based upon a commercially available microchip socket. This approach allows the silicon-based reactor die, which contains dual parallel reaction channels with more than 100 electrical contacts, to be installed and removed in a straightforward fashion without removing any fluidic and electronic connections. Various supporting microreactor functions, such as gas feed flow control, gas feed mixing, and various temperature control systems, are mounted on standard CompactPCI electronic boards. The boards are subsequently installed in a commercially available computer chassis. Electrical connections between the boards are achieved through a standard backplane and custom-built input-output PC boards. A National Instruments embedded real-time processor is used to provide closed-loop process control and... 

The approximate time/temperature characteristics of a simple on-off controller are relatively easy to visualize. If a dual output on-off control is considered, then a typical temperature/time curve can be shown as in Fig. 4.38. 

Typical temperature/time curve for a dual output on-off control... 

If a typical value of the neutral zone is 10°C, a typical value of the dead time 2 minutes, and the rate of temperature change 6°C/min, then the maximum temperature swing becomes 35°C This assumes that the rate of temperature change in heating is the same as in cooling (vj, = vj. These values are typical of a dual output on-off controller on an extruder. Because of the resulting large fluctuations in temperature, on-off control Is not very desirable if accurate temperature control is required. 

All tests were remotely controlled from a control room located approximately 800 m away from the test cell. All pressure, temperature, and flow data was recorded using a computer DAQ. A picture of the screen used to determine the LL in the tank is shown in Figure 9.7. Diodes were used in dual sense mode as temperature or liquid level sensors, as controlled on the right hand side of Figure 9.7. All data was scanned and recorded at 2 Hz. A camera was used to detect LAD breakdown, and the video feed was sent to the control room monitor to view the LAD output in real time. 

A batch chemical reactor is to be brought up to operating temperature with a dual-mode system. Full controller output supplies heat through a hot-water valve, while zero output opens a cold-mater valve fully at 50 percent output, both valves are closed. While full heating is applied, the temperature of the batch rises at, IT/min the time constant of the jacket is estimated at 3 min, and the total dead time of the system is 2 min. The normal load is equivalent to 30 percent, of controller output. Estimate the required values for the three adjustments in the optimal switching program. 

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