GE PanaFlow MV80, Руководство пользователя

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PanaFlow™ MV80 & MV82 User’s Manual 33
Chapter 2. Installation
2.5.1 DC Input Power Connections
To access the wiring terminal blocks, locate and loosen the small set screw which locks the small enclosure cover in
place. Then, unscrew the cover to expose the terminal block.
Connect 4-20 mA loop power (12 to 36 VDC at 25 mA, 1W max.) to the
+PWR
and
-PWR
terminals on the terminal
block (see Figure 20 below). Torque all connections to 4.43 to 5.31 in-lb (0.5 to 0.6 Nm). The DC power wire size must
be 10 to 20 AWG with 1/4 inch (7 mm) of insulation stripped from each conductor.
Figure 20: DC Power Connections
2.5.2 4-20 mA Output Connections
The standard PanaFlow meter has a single 4-20 mA loop, with the loop current is controlled by the meter electronics.
The electronics must be wired in series with the sensor resistor or current meter (see
Figure 20 above). The current
control electronics requires 12 volts at the input terminals to operate correctly.
The maximum loop resistance (load) for the current loop output is dependent upon the supply voltage and is given in
Figure 21 below. The 4-20 mA loop is optically isolated from the flowmeter electronics.
R
load
is the total resistance in the loop, including the wiring resistance. That is, R
load
= R
wire
+ R
sense
. To calculate the
maximum load resistance for the loop, subtract the minimum terminal voltage from the supply voltage and divide by
the maximum loop current of 20 mA, as shown in the following equation:
Figure 21: Load Resistance Versus Input Voltage
+ Pwr
– Pwr
12 to 36 VDC
R
Load
25 mA max.
R
max load
V
supply
12V
–
0.020A
----------------------------------
=
0
300
600
900
1200
12 18 24 30 36
Operating
Range R,load (ohms)
Vsupply (volts)
Vsupply
(volts)
12
18
24
30
36
Rmax
(ohms)
0
300
600
900
1200