Advantech iDAQ-731, User Manual

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9 iDAQ-731_751_763D User Manual
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2.2 Signal Connection and Pin Assignment
2.2.1 Isolated Digital Input Connection
A digital input channel senses the state of the external sensor or switch, and passes
it through a galvanic isolator to the internal circuit. Figure 2.2 shows the digital input
signal connection.
Figure 2.2 Digital input signal connection.
There are several digital input common (DICOM) pins which are shorted together
inside the device. All digital input signals are referenced to DICOM. Therefore, the
negative terminal of the external voltage sources should be connected to DICOM for
proper operation.
If the input voltage is within OFF or ON state logic level, a logic low (0) or high (1) will
be sensed, respectively. If the input voltage is between the OFF and ON state logic
levels, the result is undetermined, which may be low or high. User should ensure the
ON/OFF state voltages of the sensors or switches meet the required values. Do not
input a voltage higher than the maximum value of ON state logic level or lower than
the minimum value of OFF state logic level. The device may be damaged under such
circumstance. Refer to A1. Isolated Digital Input (iDAQ-731) for OFF and ON state
logic level for the device.
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.