Version 1.0, August 31, 2001, Copyright, Hugh Jack 1993-2001
· Input modules typically accept various inputs, depending upon specified values.
· An example of a PLC input card is shown below.
· DC voltages are usually lower, and therefore safer (i.e., 12-24V)
· DC inputs are very fast, AC inputs require a longer time (e.g., a 60Hz wave would require up to 1/60sec for reasonable recognition).
· DC voltages are flexible being able to connect to greater varieties of electrical systems.
· DC input cards typically have more inputs.
· AC signals are more immune to noise than DC, so they are suited to long distances, and noisy (magnetic) environments.
· AC signals are very common in many existing automation devices.
