Spirax Sarco RIM20, Инструкция по установке и обслуживанию, Страница: 30 / 132

IM-P198-05 MI Issue 2 30
Fig. 14 dc power connections
3.13 Input power connections
To access the wiring terminal blocks, locate and loosen the small set screw which locks the
small enclosure cover in place. Unscrew the cover to expose the terminal block.
3.13.1 dc power wiring
Connect 4-20 mA loop power (12 to 36 Vdc at 25 mA, 1W max.) to the +Loop Power and
-Loop Power terminals on the terminal block.
Torque all connections to 0.5 to 0.6 N-m (4.43 to 5.31 in lbs).
The dc power wire size must be 20 to 10 AWG with the wire stripped 7 mm (¼").
Fig. 15 Load Resistance Versus Input Voltage
3.14 4-20 mA output connections
The RIM20 flowmeter has a single 4-20 mA loop. The 4-20 mA loop current 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 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 14. 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 (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 maximum loop current, 20 mA. Thus:
The maximum resistance R
load
= R
max
= (V
supply
- 12V) / 0.020 A
R
load
12 to 36 VDC
25 mA max.
+ Pwr
- Pwr
R
load
(ohmns)
V
Supply
(volts)
Operating
range
V
supply
(volts)
R
load
(o
hm
ns
)
12 to 36 Vdc
25 mA max.
+ Pwr
- Pwr
Operating
range