GE PanaFlow MV80, Руководство пользователя

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Chapter 2. Installation
40 PanaFlow™ MV80 & MV82 User’s Manual
2.6.2 4-20 mA Output Connections (cont.)
The maximum loop resistance (load) for the current loop output is dependent upon the supply voltage and is given in
Figure 34 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 34: Load Resistance Versus Input Voltage
2.6.3 Frequency Output Connections
The frequency output is used for a remote counter. It can be scaled to output a 1 to 10 kHz signal proportional to mass
or volume flow, temperature, pressure or density.
The frequency output requires a separate 5 to 36 VDC power supply. However, there are current and power
specifications that must be observed. The output can conduct a current up to 40 mA and can dissipate up to 200 mW of
power. The output is isolated from the meter electronics and power supply.
There are three connection options for the frequency output:
•
For AC or DC powered meters, use a separate 5 to 36 VDC power supply (see Figure 35 on page 41 ). Use this
option if a specific voltage is needed for the frequency output.
•
For DC powered meters only, use the flow meter power supply (see Figure 36 on page 41 ). Use this option if
the voltage at the flow meter power supply is an acceptable driver voltage for the connected load, taking into
account that the current used by the frequency load comes from the meter’s power supply.
•
For AC powered meters only, use the internal 24 VDC power supply (see Figure 37 on page 41 ). Use this
option if the voltage of the frequency output is the same as the voltage supplied to the circuit.
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