Advantech PCI-1758 Series, Руководство пользователя

Страница: 25 / 34

19 PCI-1758 Series User Manual
C
ha
pte
r 3
Sig
na
l C
on
ne
ctio
ns
state logic level. The device may be damaged under such circumstance. Refer to
Appendix A Specifications for OFF and ON state logic level for the device.
For dry contact operation, shorting the DI pin to the GND pin results in a logic high
(1). If the DI pin is kept floating, a logic low (0) will be sensed.
Each digital input channel is equipped with a galvanic isolator, which can withstand a
large continuous voltage between external side and internal side. This prevents inter -
nal circuit from damaging when such fault condition happens.
Figure 3.7 shows how to connect an external input source to one of the card’s iso
-
lated input channels.
Figure 3.7 Isolated Digital Input Connection
3.4.3 Isolated Digital Output
An isolated digital output channel sends a signal through a galvanic isolator to control
the ON/OFF state of a MOSFET switch. The state of the MOSFET switch then
decides if the load is conducting or not. The digital output channel supports sink
(NPN) type connection as shown in below picture.
For sink (NPN) type digital output, the current flows from the load into the DO pin.
Ensure the negative terminal of the external voltage source to be connected to the
GND pin for proper operation. Both the voltage of the external voltage source and the
load current must be within the range as specified in Appendix A Specifications. The
device may be damaged if the voltage or current is beyond the maximum value.
Each digital output channel is equipped with a galvanic isolator, which can withstand
a large continuous voltage between external side and internal side. This prevents
internal circuit from damaging when such fault condition happens.
The device is also equipped with flyback diodes for each channel. The flyback diode
provide a continuous current path for inductive load to dissipate energy when the dig -
ital output channel becomes OFF. This prevents the inductive load from generating a
large back EMF which may damage the device.
Every four digital output channels are equipped with one polyswitch to limit the load
current. Do not exceed the load current value specified in Appendix A Specifications
for proper operations.