C.1 DC Input Modules
Unified Controller nv series type2 light Controller Unit Instruction Manual
113
Let R [Ω] be the cable resistance. Let Vd [V] be the proximity switch's residual
voltage. Let Zi [Ω] be the input module's proximity input impedance. In this case,
the following expresses the voltage Vi [V] that is applied between the input
terminals of the input module when the proximity switch is turned on:
Vi =
V-Vd
2R + Zi
Zi
If Vi above decreases below the minimum ON voltage of the input module, you
need to increase the input voltage or make provisions that decrease the cable
resistance R.
(6) If the input filter time constant is small in an input module such as DI934, influence
of contact chattering may cause erroneous input data to be read.
If a quick response is required, make connection with contactless equipment and
also take the noise into sufficient consideration.
(7) If a long input cable is routed, you also need to take the noise into consideration in
addition to the voltage drop that is due to the cable's conductor resistance. Note
the following items:
・
Wire the cable at the minimum distance without making unnecessary loops.
・
Separate the cable from any power line or high-frequency signal line as far as
possible. Keep it away 200 mm or more from them, or shield it with iron plate.
・
If possible, relay the cable at the inlet to the control board.
・
Consider using a shielded cable or twisted pair cable in some cases.
・
Install the bleeder resistor to lower the input impedance.
(8) If you configure the dynamic scanning input using the DC input and output
modules, you need to take into consideration the timing-off phenomenon caused
by CPU scanning as well as response lag in output and input. For the hardware, a
backflow prevention diode is required to prevent input errors caused by the
peripheral circuit. (4x4 input is shown in the following figure.)
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