51-10
Flowserve Corporation, Valtek Control Products, Tel. USA 801 489 8611
C
network
(
µ
F) < - 0.0032
22
ρ
F 0.000022
µ
F
foot foot
65
(300 + 50
+ 390)
C
network
(
µ
F)
C
cable
0.08
µ
F
0.000022
µ
F/foot
- 0.0032 = 0.08
µ
F = C
network
(
µ
F)(Max)
The voltage 12.5 V is greater than the required 12.0 V;
therefore, this system will support the Logix 500. The
Logix 500 has an input resistance equivalent to 625
Ω
at a 20 mA input current.
Cable Requirements
The Logix 520 digital positioner utilizes the HART com-
munication 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 com-
munication, cable capacitance and cable length restric-
tions must be calculated. The cable length must be lim-
ited if the capacitance is too high. Selecting a cable
with lower capacitance/foot rating will allow longer cable
runs. In addition to cable capacitance, the network re-
sistance also affects the allowable cable length.
To calculate the maximum network capacitance use the
following formula.
65
(R
barrier
+ R
wire
+ 390)
Example: R
barrier
= 300
Ω
(if present)
R
wire
= 50
Ω
C
cable
= =
Max. Cable Length =
Max. Cable Length = = 3636 ft.
Figure 9: Compliance Voltage
500
12.0 VDC
To control cable resistance, No. 24 AWG cable should
be used for runs less than 5000 feet. For cable runs longer
than 5000 feet, No. 20 AWG cable should be used.
Electromagnetic Compatibility
The Logix 520 digital positioner has been designed to
operate 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 one feet 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 positioner to restore operation.
STARTUP
Logix 500 Local Interface operation
The Logix 500 local user interface allows the user to
configure the basic operation of the positioner, tune the
response, and calibrate the positioner without additional
tools or configurators. The local interface consists of a
Quick-Cal™ button for automatic zero and span set-
ting, along with two jog buttons for spanning valve/
actuators with no fixed internal stop in the open posi-
tion. There is also a switch block containing eight
switches. Six of the switches are for basic configura-
tion settings and one is for calibration options and one
