analog signal converter

[blackseaman]

http://www05.abb.com/global/scot/sc...5750e0044f83e/$File/2CDC110004C0206_05-01.pdf

here is shown at the 3.page a nice pic , what i understand is this converter takes analog signal and converts it to another signal, but i searched through internet to learn what it makes exactly and some sites cite that analog signal converters are analog-digital converters and at this pic perhaps it means that analog signal is converted to digital signal since the signal is fed to a plc,as far as i know plcs have analog input but i am confused. so can u tell me what do these converters exactly?

 

[jraef]

Not sure if I am understanding you correctly, but here goes.

Sometimes a PLC, even if it has an analog input, can only accept a specific type of analog input. For example, the PLC can accept 0-10VDC, but you have a field device that can only put out a 4-20ma signal. The Signal Converter is used to accept the 4-20ma signal from the field and convert it to a proportionally scaled 0-10VDC analog signal that the PLC can accept. They are also used to convert to digital signals as well, it all depends on what you need and what you buy.

Another common use is to add isolation from the field device signal and the controller input so that if there is a problem at either side, it dos not harm the other side. For example let's say you have 4-20ma from a field device and a 4-20ma input in the PLC so conversion is unnecessary. But if someone accidentally connects 110VAC to the remote wires it will possibly damage the converter module but not burn out the PLC input and cause the entire process to shut down.


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