Flowserve 520si Digital Positioner - Manual (Page 7)

7
Compliance Voltage (Figure 4)
Output compliance voltage refers to the voltage limit the cur-
rent source can provide. A current loop system consists of
the current source, wiring resistance, barrier resistance (if
present), and the Logix 520 si impedance. The Logix 520 si
requires that the current loop system allow for a 12,0 VDC
drop across the positioner at maximum loop current.
CAUTION: Never connect a voltage source directly
across the positioner terminals. This could cause per-
manent circuit board damage.
In order to determine if the loop will support the Logix 520 si,
perform the following calculation.
Voltage = Compliance Voltage (@Current
MAX
)
- Current
MAX
*(R
barrier
+ R
wire
)
The calculated voltage must be greater than 12.0 VDC in or-
der to support the Logix 520.
Example: DCS Compliance Voltage = 19 V
R
barrier
= 300 Ω
R
wire
= 25 Ω
CURRENT
MAX
= 20 mA
Voltage = 19 V - 0,020 A*(300 Ω + 25 Ω)
= 12,5 V
The voltage 12,5 V is greater than the required 12.0 V; there-
fore, this system will support the Logix 520. The Logix 520 si
has an input resistance equivalent to 600 Ω at a 20 mA input
current.
7 WIRING AND GROUNDING GUIDELINES
Electrical connections: signal cable with cable passage (NPT,
PG13,5, or M20 x 1,5) to terminals 2 x 2,5 mm
Input signal: 4 – 20 mA
NOTE: Observe the minimum requirements of voltage
and equivalent electrical load: 12,0 VDC / 600 Ω / at
20 mA
To calculate the maximum network capacitance use the fol-
lowing formula.
The performance is ensured only for a minimum input cur-
rent of 3,6 mA.
For wiring, the following notes should be observed:
NOTE: The input loop current signal to the Logix 520
should be in shielded cable. Shields must be tied to a
ground at only one end of the cable to provide a place
for environmental electrical noise to be removed from
the cable. In general, shield wire should be connected
at the source. (Figure 8)
Connect the 4-20 mA current source to terminals +11 and
-12 (Figure 5).
Grounding Screw
The grounding screw, located inside the positioner cover,
should be used to provide the unit with an adequate and reli-
able earth ground reference. This ground should be tied to
the same ground as the electrical conduit. Additionally, the
electrical conduit should be earth grounded at both ends of
its run. The grounded screw must not be used to terminate
signal shield wires.
Figure 2: Dimensional Drawing of the Logix 500 si Series Digital Positioner
M8
M6
17.7 17.7
28.6
63,5
173,5
17.7
17.7
28.6
28.6
47
100
1/4" NPT
ø 10
ø 4,8
11,9
23,9
ø 10
19,9
ø 10
M 8
11,9
23,9
M 20 x 1,5 or 1/2" NPT
60
96.5