20 •• Operation Theorem
DC voltage.
The cPCI-7252 contains 16 identical opto-isolated control input
channels. The circuit diagram of the isolated input signales of channel
number 8~15 are the same as which in PCI-7250. However, the input
signals for channel number 0~7 is differential input which is shown in
the following diagram.
V
IN
1.2k
Ω
Ri
PC-814
(opto-isolator)
I
F
DInH
DInL
In addition, a single-pole filter with a time constant about 5ms is used
to filter when the AC inputs passed through.
The normal input voltage range for high state is 3 to 24VAC or DC. The
normal input range can be extended by changing the resister (Ri) to
limit the current (IF) through the PC-814 (opto-isolator to about 10mA .
The exact resister value to replace the original resister Ri (1.2K Ω) can
be calculated by the following formula.
Vin = IF X Ri
Pw = Vin X IF
For example, if the input voltage is 110V, then the Ri should be
replace by
Ri = 110 (V) / 0.01 (A) = 11 KΩ
Pw = 110 (V) X 0.01 (A) = 1.1 W
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