8051 microcontrollers

Process Dynamics and Control Introduction The field of process dynamics and control is concerned with the analysis of dynamic behavior of processes, process simulation, design of automatic controllers, and associated instrumentation. Process control as practiced in the process industries has undergone significant changes since it was first introduced in the 1940s. Perhaps the most significant influence on the changes in process control technology has been the introduction of digital computers and instruments with greater capabilities than their analog predecessors. During the past 25 years automatic control has assumed increased importance in the process industries, which has led to the application of more sophisticated techniques (Seborg, Edgar, and Mellichamp, 2004; Ogunnaike and Ray, 1995). For instrumenting and controlling a modern plant, it is necessary that an engineer has an understanding of the time-dependent behavior of typical processes. This in turn requires an apprec...

Common Issues with PC-based Data Acquisition Aside from software and programming, the most common problem users run into when putting together DAQ systems is a noisy measurement. Unfortunately, noise in DAQ systems is a complicated issue and difficult to avoid. However, it is useful to understand where noise typically comes from, how much noise is to be expected, and some general techniques to reduce or avoid noise corruption. The Low-Noise Voltmeter Standard One of the most common questions asked of technical support personnel of DAQ vendors concerns the voltmeter. Users connect their signal leads to a handy voltmeter or digital multimeter (DMM), without worrying too much about cabling and grounding, and obtain a rock solid reading with little jitter. The user then duplicates the experiment with a DAQ board and is disappointed to find that the readings returned by the DAQ board look very noisy and very unstable. The user decides there is a problem with the DAQ board and calls ...

Equivalent-Time Sampling If real-time sampling techniques are not fast enough to digitize the signal, then consider ETS as an approach. Unlike continuous, interval, or multirate scanning, complex counter/timers control ETS conversions, and ETS strictly requires that the input waveform be repetitive throughout the entire sampling period. In ETS mode, an analog trigger arms a counter, which triggers an ADC conversion at progressively increasing time intervals beyond the occurrence of the analog trigger (as shown in Fig. 18.38). Instead of acquiring samples in rapid succession, the ADC digitizes only one sample per cycle. Samples from several cycles of the input waveform are then used to recreate the shape of the signal. ETS Counter/Timer Operations Four complex timing and triggering mechanisms are necessary for ETS. They include hardware analog triggering, retriggerable pulse generation, autoincrementing, and flexible data acquisition signal routing. Hardware Analog Triggering...

Data Acquisition Software The software is often the most critical component of the data acquisition system. Properly chosen software can save you a great deal of time and money. Likewise, poorly chosen software can cost you time and money. A whole spectrum of software options exists, with important tradeoffs and advantages. Board Register-Level Programming The first option is not to use vendor-supplied software and program the DAQ board yourself at the hardware level. DAQ boards are typically register based, that is, they include a number of digital registers that control the operation of the board. The developer may use any standard programming language to write series of binary codes to the DAQ board to control its operation. Driver Software Driver software typically consists of a library of function calls usable from a standard programming language. These function calls provide a high-level interface to control the standard functions of the plug- in board. For example, a f...