Advantech PCI-1751U, User Manual

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PCI-1751U User Manual 18
If the jumper JA1 is enabled and the initial configuration is caused by a
reset, all ports will return to the states they had just prior to the reset. The
reset must be a "hot" reset (power not disconnected) for enabled JA1 to
return ports to their prior values. Otherwise, the card behaves as though
JA1 were not enabled. Refer to "Jumper settings" in Chapter 2 for more
information.
3.2.5 Dry Contact Support for Digital Input
Each digital input channel accepts either dry contact or 0 ~ 5 VDC wet
contact inputs. Dry contact capability allows the channel to respond to
changes in external circuitry (e.g., the closing of a switch in the external
circuitry) when no voltage is present in the external circuit. Figure 3-1
shows external circuitry with both wet and dry contact components, con-
nected as an input source to one of the card's digital input channels.
Figure 3.1: Wet & Dry Contact Inputs
Note: For wet contact configurations, a malfunction may occur if the
internal resistance of the voltage source is significant (> 1.5 kW). It is
advisable to connect a 1.5 kW resistor in parallel with such a voltage
source to avoid a voltage rise inside the voltage source.