VorTek SonoPro Professional S36 Series, Инструкция по эксплуатации

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Series S36 Instruction Manual Chapter 2 Installation
800120 2-23
4-20 mA Output Connections
The standard
SonoPro
® Professional Series flow meter has two 4-20 mA
loop outputs. The 4-20 mA loop current is controlled by the meter electron-
ics. The electronics must be wired in series with the sense resistor or current
meter. For convenience, the SonoPro
®
comes standard with two, 250 Ohm
resistors, for use with each 4-20 mA loop. The current control electronics re-
quire a minimum of 12 volts at the input terminals to operate correctly. 36
volts is the maximum. Another added convenience of the standard SonoPro
®
is the addition of an isolated 24 VDC power supply for powering of the 4-20
mA outputs, pulse output, frequency output, and alarm outputs (all discussed
in the sections below). The 24 VDC power supply can produce 100 mA at
maximum.
The maximum loop resistance (load) for the current loop output is dependent
upon the supply voltage and is given in Figure 2-28. The 4-20 mA loop is op-
tically isolated from the flow meter electronics.
R
load
is the total resistance in the loop, including the wiring resistance (R
load
=
R
wire
+ R
sense
). To calculate R
max
, the maximum R
load
for the loop, subtract the
minimum terminal voltage from the supply voltage and divide by the maxi-
mum loop current, 20 mA. Thus:
The maximum resistance R
load
= R
max
= (V
supply
– 12V) / 0.020 A
Figure 2-28. Load Resistance versus Input Voltage
For Hart Communications
signal loop must have a
minimum of 250 ohms load
resistance R
L
R
L
> 250
mA
Meter
Figure 2-29. Isolated 4 – 20 mA Output Using External Power Supply
Signal loop must have a
minimum of 250 ohms load
resistance R