VorTek SonoPro S34 Series, Инструкция по эксплуатации

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Series S34 Instruction Manual Chapter 2 Installation
M-000-00030 2-17
4-20 mA Output Connections
The standard
SonoPro
®
Flow Meter has two 4-20 mA loops. The 4-20 mA loop cur-
rent is controlled by the meter electronics. The electronics must be wired in series
with the sense resistor or current meter. The current control electronics require a min-
imum of 12 volts at the input terminals to operate correctly. 36 volts is the maximum.
The maximum loop resistance (load) for the current loop output is dependent upon the
supply voltage and is given in Figure 2-18. The 4-20 mA loop is optically 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 ter-
minal voltage from the supply voltage and divide by the maximum loop current, 20
mA. Thus:
The maximum resistance R
load
= R
max
= (V
supply
– 12V) / 0.020 A
Figure 2-17. 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 2-18. Isolated 4 – 20 mA Output Using External Power Supply