Digital Input Interface (FAC2100)

Digital Input Interface 

Digital Input

The FAC-2100 contains ten optically isolated digital inputs. Eight of those inputs are classified as standard inputs and the remaining two as universal inputs. The main difference between the two types is the input voltage range. The figure above shows the equivalent circuit for these inputs. Notice that each input drives an isolating infrared light emitting diode (LED). When current is supplied to the LED, the digital input is said to be in a logic high state. When current is removed from the LED, the digital input is in a logic low state. Table 1 shows the signal range associated with each logic state for each digital input type.

Both the universal and standard digital inputs, when used with a voltage source (such as the FAC-2100's auxiliary output), can be used to indicate a switch or contact closure. Use the universal digital input to interface with logic circuits. Use the standard digital input to interface with sources above 30 VDC or with AC signals.

Table 1 - Voltage ranges for the digital inputs