Watlow CAS200 User Manual
CAS200
User’s Guide
WATLOW
1241 Bundy Boulevard
Winona, MN 55987
Phone: +1 (507) 454-5300. Fax: +1 (507) 452-4507
Document No. 0600-3050-2400. Revision A
November 2008
Copyright © 2001
Watlow Anafaze
Information in this manual is subject to change without notice. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form
without written permission from Watlow Anafaze.
Warranty
Watlow Anafaze, Incorporated warrants that the products furnished under this Agreement will be free from defects in material and workmanship for a period of three years
from the date of shipment. The customer shall provide notice of any defect to Watlow
Anafaze within one week after the Customer's discovery of such defect. The sole obligation and liability of Watlow Anafaze under this warranty shall be to repair or
replace, at its option and without cost to the Customer, the defective product or part.
Upon request by Watlow Anafaze, Incorporated, the product or part claimed to be
defective shall immediately be returned at the Customer's expense to Watlow Anafaze.
Replaced or repaired products or parts will be shipped to the Customer at the expense
of Watlow Anafaze.
There shall be no warranty or liability for any products or parts that have been subject
to misuse, accident, negligence, failure of electric power or modification by the Customer without the written approval of Watlow Anafaze. Final determination of warranty eligibility shall be made by Watlow Anafaze. If a warranty claim is considered
invalid for any reason, the Customer will be charged for services performed and
expenses incurred by Watlow Anafaze in handling and shipping the returned unit.
If replacement parts are supplied or repairs made during the original warranty
period, the warranty period for the replacement or repaired part shall terminate with
the termination of the warranty period of the original product or part.
The foregoing warranty constitutes the sole liability of Watlow Anafaze and the customer's sole remedy with respect to the products. It is in lieu of all other warranties,
liabilities, and remedies. Except as thus provided, Watlow Anafaze disclaims all warranties, express or implied, including any warranty of merchantability or fitness for a
particular purpose.
Please Note
: External safety devices must be used with this equipment.
Contents
List of Figures ix
List of Tables xiii
System Overview 1
Manual Contents 1
Getting Started 2
Safety symbols 2
Contacting Watlow Anafaze 2
Product Features 3
System Diagram 4
Parts List 4
Mounting Scanner Components 5
Safety 5
Installation 7
Typical Installation 8
Safety 9
External Safety Devices 9
Mounting 10
Location 10
Recommended Tools 10
Mounting the Scanner 11
Mounting the TB50 13
System Wiring 14
Wiring Recommendations 15
Noise Suppression 16
Ground Loops 18
Power Connections 19
Watlow Anafaze i
Contents CAS200 User’s Guide
Wiring the Power Supply 19
Testing Power to the Scanner 21
Connecting the TB50 to the CAS200 22
Input Wiring 22
Sensor Connection 22
Thermocouple Connections 23
Voltage Input Connections 24
Current Input Connections 24
Serial Communications 25
EIA/TIA-232 Interface 25
EIA/TIA-485 Interface 26
EIA/TIA-485 Converters and Laptop Computers 29
Wiring Digital I/O 29
Noise Suppression 29
Digital Outputs 30
Alarm Output Connections 31
CPU Watchdog 32
Digital Inputs 32
Using the CAS200 35
Introduction 35
Front Panel 36
Front Panel Keys 36
Single Channel Display 38
Job Display 38
Change Setpoint 39
Alarms 40
Setup 41
CAS200 Menus 41
How to Enter the Setup Menus 41
How to Edit a Menu 42
Setup Global Parameters Menu 44
Load a Job 44
Save Setup to Job 45
Job Select Inputs 45
ii Watlow Anafaze
CAS200 User’s Guide Contents
Job Select Input Polarity 46
Startup Alarm Delay 46
Keyboard Lock Status 47
Scanner Address 47
Communications Baud Rate 47
Communications Protocol 48
Communications Error Checking 48
AC Line Frequency 49
Digital Output Polarity 49
External Alarm Acknowledge Input Active 49
EPROM Information 50
Setup Channel Inputs 50
Input Type 50
Display Resolution 51
Pulse Sample Time 52
Channel Name 52
Input Units 52
Input Reading Offset 53
Linear Scaling Menus 54
Display Format 55
High Process Value 56
Input Scaling High Reading 56
Input Scaling Low Process Value 56
Input Scaling Low Reading 57
Input Filter 57
Setup Channel Alarms 58
Failed Sensor Alarms 58
Global Alarms 58
Process Alarms 58
Alarm Delay 60
High Process Alarm Setpoint 60
High Process Alarm Type 60
High Process Alarm Output Number 61
Deviation Alarm Value 61
High Deviation Alarm Type 61
High Deviation Alarm Output Number 62
Low Deviation Alarm Type 62
Low Deviation Alarm Output Number 62
Watlow Anafaze iii
Contents CAS200 User’s Guide
Low Process Alarm Setpoint 63
Low Process Alarm Type 63
Low Process Alarm Output Number 63
Alarm Deadband 64
Alarm Delay 64
Manual I/O Test 65
Digital Input Testing 65
Digital Output Selection 65
Digital Output Test 66
Keypad Test 66
Troubleshooting and Reconfiguring 67
When There is a Problem 67
Returning Your Unit 68
Troubleshooting Scanners 68
Process and Deviation Alarms 68
Thermocouple Break Alarm 69
System Alarms 69
Other Behaviors 70
Corrective and Diagnostic Procedures 71
Additional Troubleshooting for Computer Supervised Systems 76
Computer Problems 76
Communications 77
Ground Channels 78
Software Problems 78
NO-Key Reset 78
Replacing the EPROM 79
Changing Communications 81
Installing Scaling Resistors 82
CAS200 Input Circuit 82
CAS200 Current Inputs 83
CAS200 Voltage Inputs 84
Scaling and Calibration 85
iv Watlow Anafaze
CAS200 User’s Guide Contents
Linear Scaling Examples 87
Example 1: 4-20mA Sensor 88
Situation 88
Setup 88
Example 2: 0-5Vdc Sensor 89
Situation 89
Setup 89
Example 3: Pulse Encoder 90
Situation 90
Setup 90
Specifications 91
CAS200 System Specifications 91
CAS200 Processor Physical Specifications 92
TB50 Physical Specifications 95
Inputs 98
Outputs 101
CAS200 Power Supply 103
Glossary 105
Watlow Anafaze v
Contents CAS200 User’s Guide
vi Watlow Anafaze
1 System Overview 1
Figure 1.1— System Components 4
2 Installation 7
Figure 2.1— System Components 8
Figure 2.2— Clearance Recommendations 10
Figure 2.3— Mounting with the Mini-Bracket 11
Figure 2.4— Mounting with the Collar Bracket 12
Figure 2.5— Mounting 13
Figure 2.6— Mounting Dimensions 14
Figure 2.7— CAS200 Series Scanner 19
Figure 2.8— Power Connections with the CAS200 Power Supply 20
Figure 2.9— Sensor Connections 22
Figure 2.10— Wiring Thermocouple Inputs 23
Figure 2.11— Wiring Voltage Input Connections 24
Figure 2.12— Wiring Current Input Connections 24
Figure 2.13— Connecting One CAS200 to a Computer Using EIA/TIA-232 26
Figure 2.14— EIA/TIA-485 Wiring 27
Figure 2.15— Recommended System Connections 28
Figure 2.16— Wiring Digital Outputs 31
Figure 2.17— Wiring Alarm Output Connections 31
Figure 2.18— Wiring Watchdog Timer Output 32
Figure 2.19— Wiring Digital Inputs 33
List of Figures
3 Using the CAS200 35
Figure 3.1— Navigating with a Single Channel Display 35
Figure 3.2— Front Panel Display 36
5 Troubleshooting and Reconfiguring 67
Figure 5.1— Removal of Electronics Assembly from Case 80
Figure 5.2— Screws Locations on PC Board 80
Figure 5.3— EPROM Location 81
Figure 5.4— Remove EPROM 81
Figure 5.5— Jumper Configurations 81
Figure 5.6— CAS200 Input Circuit 83
Watlow Anafaze vii
List of Figures CAS200 User’s Guide
7 Specifications 91
Figure 7.1— CAS200 Processor Module Dimensions 92
Figure 7.2— CAS200 Clearances with Straight SCSI Cable 93
Figure 7.3— CAS200 Clearances with Right-Angle SCSI Cable 93
Figure 7.4— TB50 Dimensions 95
Figure 7.5— TB50 Dimensions with Straight SCSI Cable 96
Figure 7.6— TB50 Dimensions with Right-Angle SCSI Cable 97
Figure 7.7— Power Supply Dimensions (Bottom View) 104
viii Watlow Anafaze
2 Installation
Table 2.1— Cable Recommendations 16
Table 2.2— Power Connections 20
Table 2.3— EIA/TIA-232 Connections 25
Table 2.4— RTS/CTS and DSR/DTR Pins in DB-9 and DB-25 Connectors 26
Table 2.5— TB50 Connections for CAS200 33
Table 2.6— TB18 Connections 34
List of Tables
5 Troubleshooting and Reconfiguring
Table 5.1— Hardware Error Messages 69
Table 5.2— Other Symptoms 70
Table 5.3— Resistor Values for CAS200 Current Inputs 83
Table 5.4— Resistor Locations for CAS200 Current Inputs 84
Table 5.5— Resistor Values for CAS200 Voltage Inputs 84
Table 5.6— Resistor Locations for CAS200 Voltage Inputs 85
6 Linear Scaling Examples
Table 6.1— Input Readings 88
Table 6.2— Scaling Values 88
Table 6.3— Input Readings and Calculations 89
Table 6.4— Scaling Values 89
Table 6.5— Scaling Values 90
7 Specifications
Table 7.1— Agency Approvals / Compliance 91
Table 7.2— Environmental Specifications 92
Table 7.3— Physical Dimensions 92
Table 7.4— Processor with Straight SCSI 93
Table 7.5— Processor with Right Angle SCSI 93
Table 7.6— Processor Connections 94
Table 7.7— TB50 Physical Dimensions 95
Table 7.8— TB50 Connections 95
Table 7.9— TB50 with Straight SCSI 96
Table 7.10— TB50 with Right Angle SCSI 97
Table 7.11— Analog Inputs 98
Table 7.12— Pulse Inputs 99
Table 7.13— Thermocouple Range and Resolution 99
Watlow Anafaze ix
List of Tables CAS200 User’s Guide
Table 7.14— Input Resistance for Voltage Inputs 100
Table 7.15— Digital Inputs 100
Table 7.16— Digital Outputs Control / Alarm 101
Table 7.17— CPU Watchdog Output 101
Table 7.18— 5Vdc Output (Power to Operate Solid State Relays) 102
Table 7.19— Reference Voltage Output (Power to Operate Bridge Circuit Sensors) 102
Table 7.20— Processor Serial Interface 102
Table 7.21— Processor Power Requirements 102
Table 7.22— Power Supply Environmental Specifications 103
Table 7.23— Power Supply Agency Approvals / Compliance 103
Table 7.24— Power Supply Physical Specifications 103
Table 7.25— Power Supply with Mounting Bracket 103
Table 7.26— Power Supply Inputs 104
Table 7.27— Power Supply Outputs 104
x Watlow Anafaze
1
System Overview
Manual Contents
This manual describes how to install, setup, and operate a
CAS200. Included are six chapters and a glossary of terms.
Each chapter covers a different aspect of the alarm scanner
and may apply to different users. The following describes
the chapters and their purpose.
• Chapter 1: System Overview provides a component
• Chapter 2: Installation provides detailed
• Chapter 3: Using the CAS200 provides an overview
• Chapter 4: Setup provides detailed descriptions of all
• Chapter 5: Troubleshooting and
• Chapter 6: Linear Scaling Examples provides
• Chapter 7: Specifications lists detailed
list and summary of features for the CAS200 series
alarm scanners.
instructions on installing the CAS200 and its
peripherals.
of operator displays used for system monitoring and
job selection.
menus and parameters for scanner setup.
Reconfiguration provides some basic guidelines for
solving operational problems and provides procedures
for changing some of the hardware options (e.g.
installing special input resistors and changing EIA/
TIA-232 to EIA/TIA-485).
three examples where linear scaling is used.
specifications of the scanner and optional components.
Watlow Anafaze 1
Chapter 1: System Overview CAS200 User’s Guide
Getting Started
The following sections provide information regarding
product features, technical descriptions, safety
requirements, and preparation for operation.
Safety symbols
These symbols are used throughout this manual:
∫
WARNING!
Indicates a potentially hazardous situation which,
if not avoided, could result in death or serious
injury.
ç
CAUTION!
NOTE!
Contacting Watlow Anafaze
Indicates a potentially hazardous situation which,
if not avoided, could result in minor or moderate
injury or property damage.
Indicates pertinent information or an item that
may be useful to document or label for later reference.
To contact Watlow Anafaze, send correspondence to:
Watlow Anafaze, Inc.
314 Westridge Drive
Watsonville, CA 95076
Our technical support and customer service departments
may be reached Monday-Friday, 8 a.m. to 5 p.m. Pacific
time:
Telephone: +1 (831) 724-3800
Email: anafazetechsupport@watlow.com
Be sure to specify CAS200 when asking for technical
support.
2 Watlow Anafaze
CAS200 User’s Guide Chapter 1: System Overview
Product Features
The CAS200 is a modular monitoring system with 16
analog inputs. It can function as a stand-alone system; the
CAS200 1/8 DIN front panel has a Vacuum Fluorescent
Display (VFD) and touch keypad for local display and local
parameter entry. You can also use it as the key element in
a computer supervised data acquisition system; the
CAS200 can be locally or remotely controlled via an EIA/
TIA-232 or EIA/TIA-485 serial communications interface.
Features include:
Direct Connection of Mixed Thermocouple Sensors:
Connect most thermocouples to the scanner with no
hardware modifications. Thermocouple inputs feature
reference junction compensation, linearization, process
variable offset calibration to correct for sensor
inaccuracies, detection of broken, shorted or reversed
thermocouples, and a choice of Fahrenheit or Celsius
display.
Automatic Scaling for Linear Analog Inputs: The
CAS200 series automatically scales linear inputs used with
industrial process sensors. Enter two points and all input
values are automatically scaled in your units. Scaling
resistors must be installed.
Flexible Alarm Outputs: Independently set high/low
process alarms and a high/low deviation band alarm for
each channel. Alarms can activate a digital output by
themselves, or they can be grouped with other alarms to
activate an output.
Alarm Outputs: You can set high/low deviation and high/
low process alarm setpoints to operate digital outputs as
latched or unlatched functions.
Global Alarm Output: When any alarm is triggered, the
global alarm output is also triggered, and it stays on until
you acknowledge it.
CPU Watchdog: The CAS200 series CPU watchdog timer
output notifies you of system failure. Use it to hold a relay
closed while the system is running, so you are notified if the
microprocessor shuts down.
Front Panel or Computer Operation: Set up and run
the scanner from the front panel or from a local or remote
computer. Watlow Anafaze offers WatView, a Windows®
compatible Human Machine Interface (HMI) software
package that includes data logging and graphing features
in addition to process monitoring and parameter setup
screens.
Multiple Job Storage: Store up to eight jobs in protected
memory, and access them locally by entering a single job
number or remotely via digital inputs. Each job is a set of
alarm conditions.
Watlow Anafaze 3
Chapter 1: System Overview CAS200 User’s Guide
Pulse Counter Input: Use the pulse counter input for
precise monitoring of motor or belt speed.
System Diagram
The illustration below shows how the parts of the CAS200
are connected. When unpacking your system, use the
diagram and parts list below to ensure all parts have been
shipped. Please don't hesitate to call Watlow Anafaze if you
have problems with your shipment, or if any CAS200
components are missing or damaged.
Figure 1.1 System Components
SCSI Cable
TB50
Digital inputs
and outputs
and pulse input
Parts List
CAS200
Signal Inputs
Power Supply
• CAS200 Scanner
• Mounting Kit
• TB50 Terminal Board
• 50-Pin SCSI Cable
• DC Power Supply
4 Watlow Anafaze
CAS200 User’s Guide Chapter 1: System Overview
Mounting Scanner Components
Install the scanner in a location free from excessive heat
(>50°C), dust, and unauthorized handling.
Electromagnetic and radio frequency interference can
induce noise on sensor wiring. Select locations for the CAS
200 and TB50 such that wiring can be routed clear of
sources of interference such as high voltage wires, power
switching devices and motors.
∫
Safety
WARNING!
To reduce the risk of fire or electric shock, install
CAS200 in a controlled environment, relatively
free of contaminants.
Watlow Anafaze has made efforts to ensure the reliability
and safety of the CAS200 and to recommend safe uses in
systems applications. Note that in any application failures
can occur.
Good engineering practices, electrical codes, and insurance
regulations require that you use independent external
safety devices to prevent potentially dangerous or unsafe
conditions. Assume that the CAS200 can fail or that other
unexpected conditions can occur.
Install high or low temperature protection in systems
where an overtemperature or undertemperature fault
condition could present a fire hazard or other hazard.
Failure to install temperature control protection where a
potential hazard exists could result in damage to
equipment and property, and injury to personnel.
For additional process safety, program a computer or other
host device to automatically reload your desired operating
parameters after a power failure. However, this safety
feature does not eliminate the need for other external,
independent safety devices in dangerous conditions.
∫
WARNING!
Watlow Anafaze 5
The CAS200 should never be used as a safety
shutdown device. It should only be used with
other approved independent safety shutdown
devices.
Contact Watlow Anafaze immediately if you have any
questions about system safety or system operation.
Chapter 1: System Overview CAS200 User’s Guide
6 Watlow Anafaze
2
Installation
This chapter describes how to install the CAS200 series
scanner and its peripherals. Installation of the scanner
involves the following procedures:
• Determining the best location for the scanner
• Mounting the scanner and TB50
• Power Connection
• Input Wiring
• Communications Wiring (EIA/TIA-232 or EIA/TIA-
485)
• Output Wiring
Watlow Anafaze 7
Chapter 2: Installation CAS200 User’s Guide
Typical Installation
The illustrations below show typical installations of the
scanner with the TB50 terminal block. Observe the
illustration below to determine potential space
requirements.
We recommend that you read this entire chapter first
before beginning the installation procedure. This will help
you to carefully plan and assess the installation.
Figure 2.1 System Components
SCSI Cable
CAS200
Signal Inputs
TB50
Digital inputs
and outputs
and pulse input
Power Supply
8 Watlow Anafaze
CAS200 User’s Guide Chapter 2: Installation
Safety
∫
WARNING!
Ensure that power has been shut off to your entire
process before you begin installation of the
scanner
Watlow Anafaze has made every effort to ensure the
reliability and safety of this product. In addition, we have
provided recommendations that will allow you to safely
install and maintain this scanner.
∫
WARNING!
External Safety Devices
In any application, failures can occur. These
failures can result in full control output (100%
power), or the occurrence of other output failures
which can cause damage to the scanner, or to the
equipment or process connected to the scanner.
Therefore, always follow good engineering
practices, electrical codes, and insurance
regulations when installing and operating this
equipment.
∫
WARNING!
External safety devices should be used to prevent
potentially dangerous and unsafe conditions upon
equipment failure. Always assume that this device can fail
with outputs full-On, or full-Off, by the occurrence of an
unexpected external condition.
Always install high or low temperature protection
in installations where an overtemperature or
undertemperature fault will present a potential
hazard. Failure to install external protection
devices where hazards exist can result in damage
to equipment, property, or human life.
Watlow Anafaze 9
Chapter 2: Installation CAS200 User’s Guide
Mounting
We recommend you mount the scanner in a panel not more
than 0.2 inches thick.
∫
Location
WARNING!
1.00 in.
(25 mm)
To reduce the risk of fire or electric shock, install
the CAS200 in a controlled environment,
relatively free of contaminants.
Install the scanner in a location free from excessive (>50°C)
heat, dust, and unauthorized handling.
Ensure there is enough clearance for mounting brackets,
terminal blocks, and cable and wire connections; the
scanner extends 7.0 in. behind the panel face and the screw
brackets extend 0.5 in. above and below it. Allow an
additional 1 to 3 inches for the SCSI cable.
Figure 2.2 Clearance Recommendations
0.50 in.
(13 mm)
7.00 in.
(178 mm)
Terminals
2.00 in.*
(51 mm)
Bezel
0.50 in.
(13 mm)
Steel Case
Recommended Tools
Use these tools to install the CAS200 series scanner and
TB50:
Panel Hole Cutters:
Use any of the following tools to cut a hole of the
appropriate size in the panel.
• Jigsaw and metal file, for stainless steel and
heavyweight panel doors.
• Greenlee 1/8 DIN rectangular punch (Greenlee part
#600-68), for most panel materials and thicknesses.
• Nibbler and metal file, for aluminum and lightweight
panel doors.
10 Watlow Anafaze
SCSI Cable
*1.00 in. with right-angle SCI cable.
CAS200 User’s Guide Chapter 2: Installation
Other Tools:
You will also need these tools:
• Phillips head screwdriver
• Flathead screwdriver for wiring
• Multimeter
Mounting the Scanner
Mount the scanner before you mount the TB50 or do any
wiring. The scanner's placement affects placement and
wiring considerations for the other components of your
system.
You receive one of two types of mounting brackets with
your scanner, the mini-bracket or the collar bracket. Refer
to the corresponding sections below for instructions.
Steps Using the Mini-Bracket
1. Cut a hole in the panel to the dimensions shown in the
illustration below. To do this, use a punch, nibbler, or
jigsaw, and file the edges of the hole.
2. Insert the scanner into the hole through the front of
the panel.
3. Screw the top and bottom clips in place: insert the
clip’s lip into the cutout in the scanner’s metal housing
just behind the front panel. Tighten the screws.
4. If you expect much panel vibration, use a rear support
for the scanner and its interconnecting cables.
Figure 2.3 Mounting with the Mini-Bracket
Maximum Panel
Thickness
1.80 in. ±0.02 in.
(45.7mm ±0.5mm)
3.63 in. ±0.02 in.
(92.2mm ±0.5mm)
Watlow Anafaze 11
0.2 in. (5mm)
Chapter 2: Installation CAS200 User’s Guide
Steps Using the Collar Bracket
Installing and mounting requires access to the back of the
panel.
NOTE! Removing the scanner chassis from its case
makes mounting easier.
1. Make a panel cutout. Refer to Figure 2.3 on page 11 for
dimensions of the cutout.
2. Slide the scanner into the panel cutout.
3. Slide the mounting collar over the back of the scanner,
making sure the mounting screw indentations face
toward the back of the scanner.
4. Loosen the mounting bracket screws enough to allow
for the mounting collar and panel thickness. Place
each mounting bracket into the mounting slots (head
of the screw facing the back of the scanner). Push each
bracket backward then to the side to secure it to the
scanner case.
5. Make sure the case is seated properly. Tighten the
installation screws firmly against the mounting collar
to secure the unit. Ensure that the end of the mounting screws fit into the indentations on the mounting
collar.
Figure 2.4 Mounting with the Collar Bracket
Panel
Bezel
Adjustable
Mounting
Brackets
(top and bottom
of scanner)
Mounting Collar
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
+
12 Watlow Anafaze
CAS200 User’s Guide Chapter 2: Installation
Mounting the TB50
There are two ways you can mount the TB50, by using the
pre-installed DIN rail mounting brackets provided or by
using the plastic standoffs. Follow the procedures for each
to mount the board.
Figure 2.5 Mounting
TB50
Mounted to
DIN Rail
TB50 Mounted
with Standoffs
NOTE! If you choose to use the standoffs, you will need
to remove the DIN rail brackets before you can
mount the board.
DIN Rail Mounting
1. Attach the SCSI connector to the TB50.
2. Snap the TB50 to the DIN rail.
3. To remove the TB50 from the rail, use a screw driver
Mounting with Standoffs
1. Remove the DIN rail mounting brackets from the
2. Select a location with enough clearance to safely
3. Place the TB50 where you will mount it and use a pen-
4. Drill and tap #6-32 holes in the locations you marked.
5. Place the TB50 where you will mount it. Insert the #6
6. There are also four smaller holes on the terminal
to unsnap the bracket from the rail with a flat-head
screw driver.
TB50.
remove the TB50, its SCSI cable and the scanner itself.
cil to trace around the standoffs.
screws in the standoffs and tighten them.
board for mounting with tie wraps. Use these holes to
secure wiring to the terminal block.
Watlow Anafaze 13
Chapter 2: Installation CAS200 User’s Guide
Figure 2.6 Mounting Dimensions
3.60 in.
2.60 in.
0.50 in.
3.40 in.
Standoffs, 4 places
for use with #6-32 screws
System Wiring
∫
WARNING! To reduce the risk of electrical shock, fire, and
Successful installation and operation of the alarm scanner
can depend on placement of the components and on
selection of the proper cables, sensors, and peripheral
components.
Routing and shielding of sensor wires and proper
grounding of components can insure a robust system. This
section includes wiring recommendations, instructions for
proper grounding and noise suppression, and
considerations for avoiding ground loops.
equipment damage, follow all local and national
electrical codes. Correct wire sizes, fuses and
thermal breakers are essential for safe operation
of this equipment.
14 Watlow Anafaze
CAS200 User’s Guide Chapter 2: Installation
ç
CAUTION! Do not wire bundles of low-voltage signal and
control circuits next to bundles of high-voltage ac
wiring. High voltage may be inductively coupled
onto the low-voltage circuits, which may damage
the scanner or induce noise and cause poor
control.
Physically separate high-voltage circuits from
low-voltage circuits and from CAS200 hardware.
If possible, install high-voltage ac power circuits
in a separate panel.
Wiring Recommendations
Follow these guidelines for selecting wires and cables:
• Use stranded wire. (Solid wire can be used for fixed
service; it makes intermittent connections when you
move it for maintenance.)
2
• Use 20 AWG (0.5 mm
Larger or smaller sizes may be difficult to install, may
break easily, or may cause intermittent connections.
• Use shielded wire. The electrical shield protects the
signals and the CAS200 from electrical noise. Connect
one end of the input and output wiring shield to earth
ground.
• Use copper wire for all connections other than
thermocouple sensor inputs.
) thermocouple extension wire.
Watlow Anafaze 15
Chapter 2: Installation CAS200 User’s Guide
Table 2.1 Cable Recommendations
Function Mfr. P/N
Analog Inputs
RTD Inputs
Thermocouple Inputs T/C Ext. Wire 2 20 0.5
Control Outputs and Digital I/O
Analog Outputs
Computer Communication: EIA/TIA-232, 422 or
485, or 20 mA
Belden 9154
Belden 8451
Belden 8772
Belden 9770
Belden 9539
Belden 9542
Ribbon Cable
Belden 9154
Belden 8451
Belden 9729
Belden 9730
Belden 9842
Belden 9843
Belden 9184
No. of
Wires
2
2
3
3
9
20
50
2
2
4
6
4
6
4
AWG
20
22
20
22
24
24
22-14
20
22
24
24
24
24
22
mm
0.5-2.5
Noise Suppression
0.5
0.5
0.5
0.5
0.2
0.2
0.5
0.5
0.2
0.2
0.2
0.2
0.5
2
4000 ft. (1219 m)
4000 ft. (1219 m)
6000 ft. (1829 m)
Maximum
Length
Symptoms of RFI/EMI
The CAS200’s outputs are typically used to drive solid state
relays. These relays may in turn operate more inductive
types of loads such as electromechanical relays, alarm
horns and motor starters. Such devices may generate
electromagnetic interference (EMI or noise). If the scanner
is placed close to sources of EMI, it may not function
correctly. Below are some tips on how to recognize and
avoid problems with EMI.
For earth ground wire, use a large gauge and keep the
length as short as possible. Additional shielding may be
achieved by connecting a chassis ground strap from the
panel to CAS200 case.
If your scanner displays the following symptoms, suspect
EMI:
• The scanner’s display blanks out and then reenergizes
as if power had been turned off for a moment.
• The process variable does not display correctly.
EMI may also damage the digital output circuit—so digital
outputs will not turn on. If the digital output circuit is
damaged, return the scanner to Watlow Anafaze for repair.
16 Watlow Anafaze
CAS200 User’s Guide Chapter 2: Installation
Avoiding RFI/EMI
To avoid or eliminate most RFI/EMI noise problems:
• Connect the CAS200 case to earth ground. The
CAS200 system includes noise suppression circuitry.
This circuitry requires proper grounding.
• Separate the 120 or 240 Vac power leads from the lowlevel input and output leads connected to the CAS200
series scanner. Do not run the digital I/O or alarm
output leads in bundles with ac wires.
• Where possible, use solid state relays (SSRs) instead of
electromechanical (EM) relays. If you must use EM
relays, try to avoid mounting them in the same panel
as the CAS200 series equipment.
• If you must use EM relays and you must place them in
a panel with CAS200 series equipment, use a 0.01
microfarad capacitor rated at 1000 Vac (or higher) in
series with a 47Ω, 0.5 watt resistor across the N.O.
contacts of the relay load. This is known as a snubber
network and can reduce the amount of electrical noise.
• You can use other voltage suppression devices, but
they are not usually required. For instance, you can
place a metal oxide varistor (MOV) rated at 130 Vac
for 120 Vac control circuits across the load, which
limits the peak ac voltage to about 180 Vac (Watlow
Anafaze part number 26-130210-00). You can also
place a transorb (back-to-back zener diodes) across the
digital output, which limits the digital output voltage.
Additional Recommendations for a Noise Immune System
It is strongly recommended that you:
• Isolate outputs through solid state relays, where
possible.
• Isolate RTDs or “bridge” type inputs from ground.
• Isolate digital inputs from ground through solid state
relays. If this is not possible, then make sure the
digital input is the only connection to earth ground
other than the chassis ground.
• If you are using EIA/TIA-232 from a non-isolated host,
either (1) do not connect any other power common
point to earth ground, or (2) use an optical isolator in
the communications line.
Watlow Anafaze 17
Chapter 2: Installation CAS200 User’s Guide
Ground Loops
Ground loops occur when current passes from the process
through the scanner to ground. This can cause instrument
errors or malfunctions.
A ground loop may follow one of these paths, among others:
• From one sensor to another.
• From a sensor to the communications port.
• From a sensor to the dc power supply.
The best way to avoid ground loops is to minimize
unnecessary connections to ground. Do not connect any of
the following terminals to each other or to earth ground:
• Power supply dc common
• TB1, terminals 5, 6, 11, 12 (analog common)
• TB1, terminal 17 (reference voltage common)
• TB1, terminals 23, 24 (communications common)
• TB2, terminal 2 (dc power common)
The CAS200 has single-ended inputs. All the negative
sensor leads are tied to the analog common. That means
there is no sensor-to-sensor isolation. Proper grounding is
critical for this unit. Take these precautions:
• Use all ungrounded or all well-grounded
thermocouples, not a mix.
• If using a mixture of thermocouples or low-voltage
inputs (<500 mV) and current inputs, connect the
negative leads of the current transmitters to terminal
17 (Ref Com) on TB1.
• If using voltage transmitters, use only sourcing
models or configuration. Sinking configurations will
not work.
• Isolate the scanner’s communication port (if used) by
using an optically isolated 232-to-485 converter.
Personal Computers and Ground Loops
Many PC communications ports connect the
communications common to chassis ground. When such a
PC is connected to the scanner, this can provide a path to
ground for current from the process that can enter the
scanner through a sensor (such as a thermocouple). This
creates a ground loop that can affect communications and
other scanner functions. To eliminate a ground loop, either
use an optically isolated communications adapter or take
measures to ensure that sensors and all other connections
to the scanner are isolated and not conducting current into
the unit.
18 Watlow Anafaze
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