Signal common, Termination – Watlow CLS200 User Manual
Page 64
Chapter 2: Installation
CLS200 Series User’s Guide
48
Watlow Anafaze
Doc.# 0600-3050-2000
To avoid unacceptable interference, use less than 10 feet
(3 m) of cable from the terminal or connector to the CLS200
serial port.
Some systems may experience problems with sensor signal
reading if the commons of multiple controllers are connect-
ed. See Signal Common on page 48.
Refer to Termination on page 48 for more on terminating
resistors.
Connect the shield drain to earth ground only at computer
or host end.
.
Figure 2.33 Recommended System
Connections
Signal Common
For usual installations, do not connect the dc commons of
the controllers together or to the converter or host device.
Use an optically isolating EIA/TIA-232-to-485 converter to
prevent problems with sensor readings.
Termination
In order for EIA/TIA-485 signals to be transmitted proper-
ly, each pair must be properly terminated. The value of the
termination resistor should be equal to the impedance of
the communications cable used. Values are typically 150 to
200
Ω
.
The receive lines at the converter or host device should be
terminated in the converter, the connector to the host de-
vice or the device itself. Typically the converter documenta-
tion provides instructions for termination.
Use a terminating resistor on the receive lines on the last
controller on the 485 line. Set JU1 inside the CLS200 in po-
sition B to connect a 200
Ω
resistor across the receive lines.
Refer to Changing Communications on page 179.
WA
TLO
W ANAF
AZE CLS200
WA
TLO
W ANAF
AZE CLS200
LOOP
LOOP
PR
OCESS
PR
OCESS
UNITS
UNITS
ALARM
ALARM
SETPOINT
SETPOINT
ST
AT
US
ST
ATUS
OUT%
OUT%
MAN
AU
TO
MAN
AU
TO
CHNG
SP
CHNG
SP
A
LA
RM
A
CK
ALARM
A
CK
RAMP
SO
AK
RAMP
SO
AK
YE
S
YES
N
O
NO
BA
CK
BA
CK
EN
TER
ENTER
WA
TLO
W ANAF
AZE CLS200
WA
TLO
W ANAF
AZE CLS200
LOOP
LOOP
PR
OCESS
PR
OCESS
UNITS
UNITS
ALARM
ALARM
SETPOINT
SETPOINT
ST
ATUS
ST
ATUS
OUT%
OUT%
M
AN
AU
TO
MAN
AU
TO
C
HN
G
SP
CHNG
SP
A
LA
RM
A
CK
ALARM
A
CK
R
AM
P
S
OA
K
RAMP
SO
AK
YES
NO
BA
CK
BA
CK
ENTER
ENTER
Serial Port
232 Communications
485 Communications
Shielded Twisted Pair Cable
Optically
Isolating
232 to 485
First CLS200
Second CLS200
Last CLS200
Converter
WA
TLO
W ANAF
AZE CLS200
WA
TLO
W ANAF
AZE CLS200
LOOP
LOOP
PR
OCESS
PR
OCESS
UNITS
UNITS
ALARM
ALARM
SETPOINT
SETPOINT
ST
ATUS
ST
ATUS
OUT%
OUT%
M
AN
AU
TO
MAN
AU
TO
C
HN
G
SP
CHNG
SP
A
LA
RM
A
CK
ALARM
A
CK
R
AM
P
S
OA
K
RAMP
SO
AK
YES
NO
BAC
K
BA
CK
ENTER
ENTER