GE DewPro MMY30, Руководство пользователя

Страница: 21 / 47

Wiring Instructions 3-1
November 2005
General Guidelines
Caution!
The DewPro system contains electronic components that
are susceptible to damage by static electricity. Proper
handling procedures must be observed during the
removal, installation, or other handling of internal boards
or devices.
Note:
If the DewPro is equipped with an optional display/user
interface, please refer to Chapter 4.
System Configuration
Various Power Supplies
Figure 3-1 below illustrates various power supplies and displays for
use with the DewPro MMY30.
Figure 3-1: Power Supplies/Displays for MMY30
Designing the Loop
When selecting a power supply, please note that the voltage at the +/-
terminal of the DewPro should not fall below 12 VDC. The maximum
loop resistance is an important measure for selection of the supply
voltage. Each device connected to the loop causes a voltage drop. For
instance, using a loop-powered display with an input impedance of
50
Ω
will cause a voltage drop of 1 VDC at 20 mA, using Ohm's law.
Connecting the loop to a PLC will cause a voltage drop across the
input.
When designing your loop, add up all voltage losses across the
devices connected to the loop and add 12 V. The sum will be the
minimum supply voltage required from the power supply. Calculate
with a 20% safety factor.