 Home
 Products
 Integration
 Tutorial
 Barcode FAQ
 Purchase
 Company
barcode reader integration with asp.net loog/I /I , p~~p~~~oint = l.og,I in Software
loog/I /I , p~~p~~~oint = l.og,I Code 128C Reader In None Using Barcode Control SDK for Software Control to generate, create, read, scan barcode image in Software applications. Code128 Generator In None Using Barcode encoder for Software Control to generate, create Code 128 Code Set C image in Software applications. P, wig Concentration, g/l
Recognizing Code 128 In None Using Barcode recognizer for Software Control to read, scan read, scan image in Software applications. Painting Code128 In Visual C# Using Barcode maker for .NET framework Control to generate, create Code 128 image in .NET framework applications. Concentrated
Encode Code 128 Code Set C In .NET Framework Using Barcode drawer for ASP.NET Control to generate, create USS Code 128 image in ASP.NET applications. Code 128A Generator In VS .NET Using Barcode generation for Visual Studio .NET Control to generate, create Code128 image in .NET applications. solution
Making Code 128 Code Set C In VB.NET Using Barcode creator for Visual Studio .NET Control to generate, create USS Code 128 image in .NET framework applications. EAN128 Generation In None Using Barcode encoder for Software Control to generate, create EAN / UCC  13 image in Software applications. Process stream 1 . 0 I/min % Encode Barcode In None Using Barcode generation for Software Control to generate, create bar code image in Software applications. Make Code 39 Extended In None Using Barcode drawer for Software Control to generate, create Code 3/9 image in Software applications. 1.0 min needed for analysis I  Dial
DataMatrix Drawer In None Using Barcode creation for Software Control to generate, create Data Matrix image in Software applications. Code 128 Code Set B Creation In None Using Barcode encoder for Software Control to generate, create ANSI/AIM Code 128 image in Software applications. Chemist
Drawing UPC  E0 In None Using Barcode drawer for Software Control to generate, create UPCE image in Software applications. Printing Barcode In Visual Studio .NET Using Barcode creation for ASP.NET Control to generate, create barcode image in ASP.NET applications. FIGURE P261 EAN13 Reader In None Using Barcode scanner for Software Control to read, scan read, scan image in Software applications. Encoding Data Matrix 2d Barcode In ObjectiveC Using Barcode creator for iPhone Control to generate, create Data Matrix 2d barcode image in iPhone applications. CHAPTER
Code 39 Extended Encoder In ObjectiveC Using Barcode creation for iPhone Control to generate, create Code39 image in iPhone applications. Printing Bar Code In C# Using Barcode encoder for Visual Studio .NET Control to generate, create bar code image in Visual Studio .NET applications. DESIGN OFSAMPLEDDATA CONTROLLERS
Barcode Maker In ObjectiveC Using Barcode generation for iPhone Control to generate, create bar code image in iPhone applications. Generate Linear Barcode In Visual C# Using Barcode creation for Visual Studio .NET Control to generate, create 1D Barcode image in Visual Studio .NET applications. In this chapter, sampleddata control theory will be applied to the design of directdigital control algorithms. In the most general terms, directdigital control is the automatic control of a process by means of a digital computer. Today the singlestation, analogtype continuous controller (pneumatic or electronic) has been almost completely replaced by an instrument that is essentially a small, selfcontained digital computer. Such instruments are described as microprocessorbased controllers. This change, of course, was brought about by the great decrease in the cost of computing components and the tremendous increase in the speed of computation. In this chapter, the design philosophy for designing special purpose controllers will be developed and illustrated with some examples. The block diagram of the control system to be considered is shown in Fig. 27.1 The elements of the block that are implemented by the computer are enclosed by a dotted line and labeled computer. These elements, which consist of two impulsemodulation switches, the Ztransform of the digital control algorithm D(z), and the zeroorder hold Gh( s), will be described later. For the moment, it is necessary to understand only the general operating features of the control system. To simplify the discussion, Gp(s) in Fig. 27.1 contains the valve, the currenttopressure converter, and the process. The transfer function for the measuring element has been taken as one; for this reason, no measurement block is shown in the feedback path of Fig. 27.1. The output from the hold is a current (or voltage) signal. 405 SAMPLEDDATA
CONTROL
SYSTEMS
I      Computer                     _ I 0 FIGURE 271 I 2T
I 3T
I 4T
Block Diagram for a computer control system.
Every T units of time, the computer reads and stores the measured value of the process variable C. The computer operates on this signal, according to the algorithm D(z) stored in it, to produce a signal to the valve M,. It is assumed that the computation of M, is instantaneous, relative to the sampling period of the process. For many chemical processes that am slow, this is a reasonable assumption. By means of the hold, the signal to the valve, M,, is held constant (i.e., clamped) between sampling instants. Consequently, the valve response during transient operation of the process will resemble a stairstep function. The control algorithm is simply a mathematical description that tells the computer how to calculate the signal to the valve each sampling instant. The digital computer implements an algorithm of the form (27.1) m(nT) = &ieK n  i)T]  Ahjm[(n  j)T] i=o j=l This equation gives the value at which me(t) is to be held constant during the following sampling period, that is, m&) = m(nT) for nT I t < (n + l)T The term T is the sampling period and gi and h j are constants. The set of constants (gi, hj) constitutes the control algorithm. In the following pages, methods will be developed for finding these constants for a specific design of a controller. To understand Eq. (27.1) more readily, consider the case where k = 2 and p = 2. If we want to compute m at the onehundredth sampling instant, Eq. (27.1) is written m(lOOT) = gae(lOOT) + gle(99T) + gze(98T)  hlm(99T)  hzm(98T) DESIGN
SAMPLEDDATA
CONTROLLERS
97T 98T 99T 100T 102T 101T 103T t FIGURE 272 Qpical relationship between m,(t) and e(r) for a computer control system. Figure 27.2 illustrates the nature of the signals used in this expression for m(lOOT). Notice that m(lOOT) is computed instantaneously at t = 1OOT. For this particular example, the computation requires the present value of error, two past values of error, and two past values of manipulated variable. The more constants (gi, hj) in the algorithm, the more complex it becomes in terms of computer storage and computer time needed to solve the algorithm. To illustrate how an algorithm of the fotm of Eq. (27.1) is derived, several algorithms will be derived for a process consisting of a firstorder process with transport lag. ALGORITHMS FOR A FIRSTORDER WITH TRANSPORT LAG MODEL A variety of algorithms will be derived for a process with a transfer function that is firstorder with transport lag, that is, G,(s) = 5 (27.2) Figure 27.1 is redrawn as Fig. 27.3 with GP(s) expressed as a firstorder process with transport lag and G&) expressed as a zeroorder hold. In Fig. 27.3 the clamped signal M, is obtained from the zeroorder hold, which obtains its input

