Flowserve 520si Digital Positioner - Manual (Page 8)

8
8 CABLE REQUIREMENTS
The Logix 520 si digital positioner utilizes the HART commu-
nication protocol. This communication signal is
superimposed on the DC 4-20 mA current signal. The two
frequencies used by the HART protocol are 1200 Hz and 2200
Hz. To prevent distortion of the HART communication, cable
capacitance and cable length restrictions must be calculated.
The cable length must be limited if the capacitance is too high.
Selecting a cable with lower capacitance/mm rating will allow
longer cable runs. In addition to cable capacitance, the net-
work resistance also affects the allowable cable length.
65Ω
(R
barrier
+ R
wire
+ 390Ω)
Example:
R
barrier
= 300 Ω (if present)
R
wire
= 50 Ω
C
cable
= =
Max. Cable Length =
Max. Cable Length = = 1111 m
To control cable resistance, No. 24 AWG cable should be used
for runs less than 1500 m. For cable runs longer than this,
No. 20 AWG cable should be used.
Electromagnetic Compatibility
The Logix 520 si digital positioner has been designed to op-
erate correctly in electromagnetic (EM) fields found in typical
industrial environments. Care should be taken to prevent the
positioner from being used in environments with excessively
high EM field strengths (greater than 10 V/m). Portable EM
devices such as hand-held two-way radios should not be used
within 30 cm of the device.
Ensure proper wiring and shielding techniques of the control
lines, and route control lines away from electromagnetic
sources that may cause unwanted noise. An electromagnetic
line filter can be used to further eliminate noise (FLOWSERVE
Part Number 10156843).
In the event of a severe electrostatic discharge near the
positioner, the device should be inspected to ensure correct
operability. It may be necessary to recalibrate the Logix 520 si
positioner to restore operation.
9 STARTUP
9.1 Logix 520 si Local Interface
The Logix 520 si local user interface allows the user to
configure the basic operation of the positioner, tune the re-
sponse, and calibrate the positioner without additional tools
or configurators. The local interface consists of a Quick-Cal™
button for automatic zero and span setting, along with two
jog buttons for spanning valve/actuators with no fixed inter-
nal stop in the open position. There is also a switch block
containing eight switches. Six of the switches are for basic
configuration settings, two are for calibration options. There
is also a rotaryselector switch for adjusting the positioner gain
Figure 3: Logix 520 si Local Interface
72 ρ F 0.000072 µ F
m m
C
network
( µ F)
C
cable
0,08 µ F
0.000072 µ F/m
- 0,0032 = 0,08 µ F = C
network
( µ F)(Max)
C
network
( µ F) < - 0,0032
65
(300 + 50 + 390)
Enhanced
Quick-Cal
Configuration
Switches
Autotune
Lockout
Switch
4-20 mA input
with HART
Communications
Quick-Cal Button
Gain Selector
Jog Calibrate
Buttons
LED Status
Lights
Terminals for Optional Limit Switches