Analogue signals

In order to be able to reduce prices, even more and more test- and measurement systems are integrated on PC-boards. The powerful and inexpensive PC eomponents can be directly u.sed for these (virtual) instruments. The limited dimensions of the PC boards require a reduction to the absolute necessity of the electronic components. Analogue signal proeessing must carried out by software as far as possible. 

Another approach to the control of batching systems is to use a relatively simple scale indicator which does nothing but supply weight data to a controUer such as a PLC, which in turn controls the fiH and discharge system. The communications between the scale and controUer can be serial such as RS-232, or it can be an analogue signal such as 4-20 m A. While this system minimises operator interaction with the scale, it sacrifices speed and accuracy because of the relatively slow communications. 

Not in the class of digital recording storage media are video CDs with diameters of 200 and 300 mm, respectively. These are storage disks for recording the analogue signal of videos and are of air-sandwich constmction with two poly(methyl methacrylate) disks. 

Once the desired control action has been transformed to an analogue signal, it is transmitted to the final control element over the transmission lines. However, the final control element s actuator may require a different type of signal and thus another transducer may be necessary. Many control valve actuators utilise a pressure signal so a current-to-pressure (I/P) transducer is used to provide a pressure signal to the actuator. 

D/A Converter eonverts digital signals into analogue signals suitable for driving aetuators and other deviees. 

Digital displays began to replace analogue meters in the late 19S0s and improvements were made in the conversion of analogue signals into digital output. 

The interface receives, conditions and digitizes the analogue signals (those given by a beam, an ionic current, temperatures, voltages) output by the mass spectrometer and sends them to the computer. It acts an analogue-to-digital converter (ADC). 

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