Wednesday, April 25, 2012

Analog Input and How It Works





In operating and monitoring the PLC system and computer, sometimes people have to deal with analog input. There’re basic differences of the analog input and the digital input and the implementation is quite different from one another. So how does the analog input work, anyway?

Analog Input: Understanding It
Unlike the digital input, the analog input is using some kind of volume control system. In digital signals, the control is using binary codes of 0 and 1. Since the analog input is using volume controls, the value can range between 0 and full scale mode. These values will be interpreted by the PLC as integer value. The analog signal uses current of voltage mode – depending on which one is used by the system – with proportional magnitude that goes along with the whole processing value signals. For instance, a 0-10V analog input from 4-20mA would be changed into integer 0-32767 value. That’s how the analog input works.

Analog Input: How to Make it Running
People need to keep the continuous value voltage sampled in order to do the analog input. Once the value is sampled, then it will be converted into numeric values by ADC or Analog to Digital Converter. The sampling process isn’t instant because each sample has to have a starting and stopping time. That’s why it’s called as sampling time because each sample does require certain time to complete. Sampling period is the time between each sample. Sampling period is often bigger than the sample time. Analog input can be used in any industrial use and implementation, but this type of input is usually done and implemented in:
• Music recording. Music technology is using the integral part of ADC. When music production has been completed on the computers, the ADC is needed to make data stream that will be kept on digital file or compact disc. This type of input is also common when used in TV or radio broadcasting.
• Signal digital process. When the analog signal has to be converted or processed, and then stored, or transported in the form of digital data, a fast ADC converter is usually used, like the one used in a TV tuner card, where the microcontrollers of 8 bit, 10, 12, and 16 bit are used. But it’s also possible to use fast ADC for certain applications, such as software defining radio application using the oscilloscopes digital storage. That’s the main basic of analog input, signal, and its implementation.



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