User manual

13 PCI-1750 User Manual
Chapter 3 Operation
3.2.4 Isolated Inputs
Each of 16 isolated digital input channels accepts dry contacts or 5 ~ 50 V
DC
voltage
inputs. All sixteen input channels share 3 ground pins and one extended ground ter-
minal block (CN5). Figure 3.1 shows how to connect an external input source to one
of the card's isolated input channels.
Note for wet contacts: A malfunction might occur in cases where the internal resis-
tance of a voltage source under wet contacts is significant (>5 kW). It is advisable to
connect a parallel 5 kW, 0.5 W resistor to avoid a voltage rise inside the voltage
source.
Figure 3.1 Connecting external input source
Warning!
Be careful when wiring digital input cables. Never apply a negative volt-
age to an isolated input pin, as this may damage the PCI-1750.