Regulators microprocessor

There are very few synchronous buck controllers on the market that are not targeted to the -i-5 to 1.8 V microprocessor local regulator application (i.e., Vm of -1-12 V and Ki of -i-5 V). Also ICs that bring out enough functions to pins so that one may tailor its performance to the application. I threw out two entire product offerings from two major California companies (not to throw stones) and found only one part that fits my needs, the UC3580-3 from Unitrode/TI. 

Fig. 2.1 Schematic diagram of the CMR [22]. 1, reactants for processing 2, metering pump 3, pressure transducer 4, micro-wave cavity 5, reaction coil 6, temperature sensor 7, heat exchanger 8, pressure regulator 9, microprocessor controller ...

An automated system, by definition, should perform a required act at a predetermined point in the process and should have a self-regulating action. This implies that intervention by the analyst is not required during the procedure and that only those systems that incorporate a microprocessor or computer to control and monitor their performance can be designated as automated. Some systems may not comply strictly with this definition but are a valuable means of mechanizing laboratory activities. 

Pressures within the optical cells are adjusted using a microprocessor-controlled supercritical fluid syringe pump (Isco model SFC-500). The temperature of the cylinder head is regulated using a VWR 1140 temperature bath. The output from the pump is directed through a 2 /xm fritted filter and a series of valves into the optical high pressure cell which is temperature controlled ( 0.1 °C) by a Lauda RLS-6 temperature bath. The local temperature of the optical cell is determined using a thermocouple (Cole Palmer) placed directly into the cell body. 

It is important to recognize that a production reactor is not simply a reaction chamber. If it is a low pressure unit, there will be a vacuum system which can be quite complex. There will be a gas panel which regulates gas mass flow into the chamber. The method of heating the wafers and/or the entire chamber has to be chosen carefully. Wafer transport involves many tradeoffs, and for batch systems if any degree of automation is required, will be quite involved. Finally, most production reactors these days operate under microprocessor control, and quite a lot of software must be developed. 

Gradient Devices. Gradient devices can also be divided into two types high pressure and low pressure. In a typical low pressure system (depicted in Figure 9.22), various proportions of up to three solvents are mixed before they enter the high pressure pump. The proportions are regulated by valves that are in turn controlled electronically with microprocessors. 

The equipment used in the unit operations is complex and microprocessor controlled to allow the execution of process recipes. However, advanced control schemes are rarely invoked. The microprocessor adjusts set points according to some sequence of steps defined by the equipment manufacturer or the process operator. Flows, pressures, and temperatures are regulated independently by off-the-shelf proportional-integral-derivative controllers, even though the control loops interact strongly. For example, fluorine concentration, substrate temperature, reactor pressure, and plasma power all influence silicon etch rates and uniformity, but they are typically controlled independently. 

The art of trade-off has to be accepted in the adjustment of controllers and in the selection of suitable control elements. This action is taken since not all demands can be met in an optimal manner at the same time. Controllers operate in a digital mode and employ microprocessors. The input signal is converted into a numerical value and mathematically manipulated. The results are summarized to obtain an output signal. This signal regulates the power output in such a way that the temperature is maintained at the set value.155... 

Ambient condition vapor phase reactants are stored in gas cylinders, generally in a compressed state. Subsequent to pressure regulation, their flows generally are measured with mass flow controllers which give high accuracy and permit microprocessor control of vapor phase flows. 

Fig. 12.4 Electronic flow controller (EFC) in a gas chromatograph, (a) Capacity pressure transducer, (b) Pneumatics of the EFC. (c) Control loop regulation by means of two microprocessors. (Courtesy of Hewlett-Packard).

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