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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.

3.2.6 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 and 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.

1.5 K

Ω

0.5 W

PC 5V

10 K

Ω

Buffer

Dry Contact: Open High

Close Low

Wet Contact: 2.0~5.25 V

High

0~0.8 V

Low

External Internal

Resistor

Parallel

1 2 ... 17 18 19 20 21 22 23 24 25 26 27 ... 37 38

Brak uwag

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