Acces I/O products E-RDAG12-8, Руководство пользователя, Страница: 10 / 38

Power Required
Power can be applied from the computer's +12VDC power supply for the opto-isolated section
via the serial communication cable and from a local power supply for the rest of the unit. If you do not
wish to use power from the computer, a separate power supply isolated from the local power supply may
be used for the opto-isolated section. The power used by this section is minimal (less than 0.5W).
Low power version:
• Local Power: +12 to 18 VDC @ 200 mA. (See box that follows.)
• Opto-Isolated Section: 7.5 to 25 VDC @ 40 mA. (Note: Due to the small amount of
current required, voltage drop in long cables is not significant.)
High power version:
• Local Power: +12 to 18 VDC at up to 2 ½ A, and -12 to -18V at 2A depending
on the output load drawn.
• Opto-Isolated Section: 7.5 to 25 VDC @ 50 mA. (Note: Due to the small amount of
current required, voltage drop in long cables is not significant.)
Note
If the local power supply has an output voltage greater than 18VDC, you can install a Zener diode
Z
in series with the supply voltage. The voltage rating of the Zener diode (V ) should be equal to
I I
V -18 where V is the power supply voltage. The power rating of the Zener diode should be
$
Z
V x0.12 (watts). Thus, for example, a 26VDC power supply would require using an 8.2V Zener
diode with a power rating of 8.2 x 0.12
.
1 watt.
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Manual MRDAG12-8H.Bc2