Analog Signal

Before going too much further, we should talk a bit about what a signal actually is, electronic signals specifically. The signals we're talking about are time-varying "quantities" which convey some sort of information. In electrical engineering the quantity that's time-varying is usually voltage (if not that, then usually current).

Most data acquisition signals can be described as analog, digital, or pulse. In most control applications, analog signals range continuously over a specified current or voltage range, such as 4-20 mA or 0-10 VDC. Analog signals represent continuously variable entities such as temperatures, pressures, or flow rates.

We have seen analog signals in use in nearly every type of signal processing and consumer electronics application imaginable.

In transmitting analog signals across a process plant or factory floor, one of the most critical requirements is the protection of data integrity. However, when a data acquisition system is transmitting low level analog signals over wires, some signal degradation is unavoidable and will occur due to noise and electrical interference