Watlow 942 User Manual
Series 942
TOTAL
CUSTOMER
SATISFACTION
User's Manual
CUSTOMER
SATISFACTION
1241 Bundy Blvd., P.O. Box 5580, Winona, MN 55987-5580, Phone: 507/454-5300, Fax: 507/452-4507
W942-XUMN Rev. R00
June, 1995
Supersedes:
W942-MA40-9305
1/4 DIN
Microprocessor-Based
Ramping Control
Watlow Controls Watlow Controls
Watlow Controls
Watlow Controls Watlow Controls
Made in the U.S.A.
$10.00
Printed on Recycled Paper
2
WATLOW Series 985 User's Manual Appendix
Page Item
Chapter 1
4 Starting Out With The Watlow Series 942-
4 General Description
5 Opening the 942
5 Set the DIP Switches
Chapter 2
6 How To Install And Wire The Series 942-
6 System Planning
6 Installation Information
7 Dimensional Information
8 Wiring The Series 942
8 Sensor Installation Guidelines
9 Input Wiring
11 Output 1 Wiring
15 Output 2 Wiring
17 Auxiliary Wiring
20 System Wiring Example
Chapter 3
21 How To Use the Keys And Displays
Chapter 4
22 How To Setup The Series 942
22 Entering The Setup Menu
23 Setup Parameters
28 Operation Menu and Parameters
Chapter 5
31 Programming the Seres 942
31 Program Menu
32 Program Parameters
34 Running the Series 942
35 Resume a Profile
36 Event Outputs
37 Multiple Profiles
37 Jumploops
38 Programming a Ramping Profile
38 Running Your Profile
39 Editing Your Profile
Chapter 6
How To Tune and Operate
40 Tuning - Automatic and Manual
42 Changing the Auxiliary Jumper Position
42 Using Alarms
44 Error Code Messages & Actions
Appendix 1
46 Specification
48 Model Number Information
Appendix 2
49 Installation Guidelines For Preventing Noise
51 Eliminating Noise
52 Checking For Ground Loops
52 Noise Suppression Devices Available…
53 Line Filtering Configurations For Controls
Appendix 3
54 Entering the Calibration Menu
56 Calibration Procedures
64 Glossary
66 Index
67 Warranty/Returns
Contents
Figures, Tables, Charts
Page Item Figure
4 Series 942 Input & Output Overview 1
5 How to Open the Series 942 2
5 DIP Switch Location and Orientation 3
6 Overview of the Series 942 4
8 Series 942 Faceplate Dimensions 5
8 Series 942 Panel Cutout Dimensions 6
8 Series 942 Sideview Dimensions 7
9 120 VAC Power Wiring 8
9 240 VAC Power Wiring 9
10 Thermocouple Wiring Diagram 10
10 RTD Wiring Diagram 11
11 0 - 5 Process Input Wiring Diagram 12
11 4 - 20 Process Input Wiring Diagram 13
12 Solid State Relay, Output 1 Wiring 14
12 DC (Open Collector) Output 1 Wiring 15
13 6 Amp Mechanical Relay, Output 1 Wiring 16
13 4 - 20mA Process, Output 1 Wiring 17
14 0 - 5VDC Process, Output 1 Wiring 18
14 S.S. Relay, w/o contact supp., Output 1 19
15 S.S. Relay, Output 2 Wiring Diagram 20
15 DC (open Collector), Output 2 Wiring 21
16 6A Mechanical Relay, Output 2 Wiring 22
16 S.S. Relay, w/o contact supp., Output 2 23
17 Auxiliary Option 1, 1 - 6 Amp Relay 24
17 Auxiliary Option 2, 2 - 6 Amp Relays 25
18 Auxiliary Option 3, 6 Amp Relay/0-5ret. 26
18 Auxiliary Option 4, 6 Amp Relay/4-20ret. 27
19 Auxiliary Option 5, None/0-5Retransmit 28
19 Auxiliary Option 6, None/4-20mA Retransmit 29
20 System Wiring Example 30
21 Series 942 Keys and Displays 31
22 Entering the Setup Menu 32
22 The Setup Menu 33
28 The Operation Menu 34
31 The Program Menu 35
34 The Run Menu 36
37 Guaranteed Soak Deviation Example 37
42 Auxiliary Jumper Location 38
43 Deviation Alarm Example 39
43 Alarm Display Examples 40
44 Error Code Display Example 41
53 Differential Mode Filter Wiring 42
53 Common Mode Filter Wiring 43
53 Combination Filter Wiring 44
54 The Calibration Menu 45
55 Calibration Parameters 46
Tables
26 Input Ranges 1
27 Setup MenuParameters/Description 2
30 Operation Menu Parameters/Description 3
38 Series 942 Ramp and Soak Profile 4
39 Editing Your Profile, steps 4 - 7 5
52 Noise Suppression Device Ratings 6
57 RTD Settings 7
Charts
35 Master Step Chart 1
Appendix WATLOW Series 985 User's Manual
3
Starting Out
Starting Out
Chapter 1
The Watlow Series 942,
A Microprocessor-Based Control
Figure 1 Series 942 Input and
Output Overview.
Single Input Type J, K, T, N, R, S, B, C or Pt2
Thermocouple, RTD or Process
RS-422A, RS423A
(RS-232C compatible), or EIA-485
Optional Computer
Interface
Dual Outputs-
PID or ON/OFF, User Selectable
Output 1
Heat or Cool
Output 1
Auto-tuning
(Heat only)
Output 2
Heat, Cool or None
Dual Alarms/Events
Retransmit Output
(Up to 10 Slaves)
Process Set Point
General Description
Welcome to the Watlow Series 942, a 1/4 DIN microprocessor-based ramping
temperature control. It is a single input, dual output, auto-tuning control with 24
step program capability and easy fixed set point operation. The 942 accepts a
Type J, K, T, N, R, S, B, C or Platinel 2 thermocouple, RTD, or process input. The
primary output is heating or cooling, while the secondary output can be heating,
cooling or none.
With the Series 942 you can select either PID or ON/OFF for Output 1 or 2. You
can input a complete set of PID parameters for both outputs, including proportional
band, reset/integral and rate/derivative. You can also select automatic tuning for
Output 1 while in the heating mode. By setting either output's proportional band to
zero, the Series 942 becomes a simple ON/OFF control with the switching differential selectable under the HYS Setup parameter.
Two optional auxiliary outputs may be alarms or events. An event is an ON/OFF
mechanical relay output. Events are based on time, and can trigger peripheral
equipment or processes. An optional retransmit output is offered in lieu of one of
the auxiliary outputs. Select either retransmit of process variable or set point.
Operator-friendly features include automatic LED indicators to aid in monitoring and
setup, as well as a calibration offset at the front panel. The Watlow Series 942
automatically stores all information in a non-volatile memory.
4
WATLOW Series 942 User's Manual
Getting Started, Chapter 1
How to Open the 942
Before going further, open the Series 942 and pull the control chassis from its case.
Here's how:
The control chassis fastens to the case with a single standard screw located on the
!
LOCK
Three strip connector plugs, in the rear of the control chassis, feed power and
signals through the back of the case to the terminal strips. These plugs will let go
as you pull.
Starting Out
Starting Out
Figure 2 How to Open the
Series 942.
!
WARNING:
The front panel
screw turns 90
only. Do not apply
excessive force or
turn the screw more
than 90°.
°
When removing the Series 942 control from its case, pull firmly but gently. When
returning the control to the case, be sure you have the top up to match the plugs
with the case. The 942 will not fit in the case upside down, but check to be sure it
is oriented correctly. Press the unit in firmly, then turn the front panel screw
clockwise to secure it. This insures proper electrical contact.
How to Set the DIP Switches
The Watlow Series 942 has a Dual In-line Package (DIP) switch inside the control
on the A007-1954 circuit board (middle board). The location of the board and
switch appear below. The switches are clearly numbered. When Switch #1 is ON,
the Setup parameters can be viewed but not changed. When Switch #2 is ON, it
provides battery backup of the Run parameters. When the control leaves the
factory, both switches are OFF.
1 Hardware lockout of
Hardware Lockout of
1
Setup parameters
SETUP Parameters
2
2 Battery backup of the
Battery Discharge for
Storage
Run parameters
(Factory default is OFF)
Control Chassis - Top View
Figure 3 DIP Switch Location
and Orientation.
NOTE:
The lithium battery
has a life of approximately ten years.
When the battery
expires, Pout and
Run are affected
(see Chapters 4 & 5).
Return the unit to
the factory for a
replacement.
Getting Started, Chapter 1
WATLOW Series 942 User's Manual
5
Installation
Chapter 2
How to Install and Wire the Series 942
System Planning
This chapter tells you how to install the Series 942. All mounting and wiring
information is right here. Because Watlow controls are thoroughly tested and
"burned in" before leaving the factory, the Series 942 is ready to install when you
receive it.
But before you begin working, read through this chapter to gain an understanding
of the entire installation. Consider sensor installation carefully. For detailed
information you'll need to look at the noise reduction guidelines in the Appendix of
this manual before making your panel cutout.
Installation Information
NOTE:
Removing the Series
942 chassis from its
case may make
mounting easier.
!
WARNING:
The front panel
screw turns 90°
only. Do not apply
excessive force or
turn the screw more
than 90°.
The Series 942 mounts in a panel cutout with two brackets, shipped with your
control. These brackets hold the case against the front panel. The Series 942
behind-panel dimensions are 3.6" (90 mm) high by 3.6" (90 mm) wide by 6" (152
mm) deep. Figure 5 on the next page shows the dimensions of the front panel
bezel. The 942 weighs 2.75 lbs. (1.25 kg) max.
For dimensional and mounting information, including the location of mounting
brackets and size of the front panel cutout, see Figures 5 through 7 on the next
page. Your panel's thickness can be from 0.06" (1.5 mm) to 0.25" (6.3 mm).
Installation Procedure
Follow this procedure to mount the Watlow Series 942 Temperature Control:
1. Make a panel cutout per the dimensions in Figure 6.
2. Remove the 942 from its case by turning the front panel screw 90° counterclockwise (CCW). Grip the bezel firmly and pull the control chassis out of the
case.
!
3. Place the case in the cutout you just made.
4. Attach the mounting brackets either to the top and bottom, or to both sides of
the unit.
5. Tighten the mounting brackets securely against your panel.
6
WATLOW Series 942 User's Manual
6. Insert the control chassis into its case and press the bezel to seat it. Turn the
front panel screw 90° clockwise (CW) to lock the control in place. The hardware installation is complete. Proceed to the wiring section from here.
Install and Wire, Chapter 2
3.81" sq.
m
(97 mm)
Dimensions
3.81" sq.
(97 mm)
Figure 4 Series 942
Dimensions.
0.92"
(23 mm)
Your Panel
Your Panel
Thickness
Thickness:
0.06" to 0.25"
0.06 to 0.25
(1.52 to 6.35mm)
(1.524 to 6.35mm)
6.0"
(152 mm)
Bezel
Mounting Bracket
3.622 to 3.653
3.62" to 3.65"
(92.00 to 92.79mm)
(92 to 93 mm)
Panel
Cutout
3.63" X 3.63"
3.625 x 3.625
(92.08 X 92.08 mm)
(92.08 x 92.08mm)
Nominal
(90 mm ± 0.381)
3.62" to 3.65"
(92 to 93 mm)
(97 mm)
3.6" ± 0.015"
3.622 to 3.653
(92.00 to 92.79m
3.8"
Figure 5 Series 942
Panel Cutout
Dimensions.
Install and Wire, Chapter 2
NOTE:
k
All dimensions in inches.
WATLOW Series 942 User's Manual
7
Power Wiring
NOTE:
For 50 or 60Hz
operation, no
adjustment or
jumper placement
is necessary.
Figure 6 120 VAC Power
Wiring.
How to Wire the Series 942
The Series 942 wiring is illustrated by model number option. Check the terminal
designation sticker on the control and compare your model number to those
shown here and to the model number breakdown in the Appendix of this manual.
Series 942 internal circuits appear "inside" the line drawing of the 942, while
connections and terminal designations appear "outside" the line drawing. All
outputs are referenced to a de-energized state. The final wiring figure is a typical
system example.
When you apply power without sensor inputs on the terminal strip, the Series 942
displays "- - - -" in the Upper display, and Er7 in the Lower display. This error
indicates an open sensor or A/D error. Remove power to the control and connect
the sensor properly, see Page 10. All wiring and fusing must conform to the
National Electric Code and to any locally applicable codes as well.
Fuse
11
12
13
120 VAC
L1
L2
Earth Ground
CAUTION:
To avoid potential
electric shock, use
National Electric
Code (NEC) safety
practices when
wiring and connecting this unit to a
power source and to
electrical sensors or
peripheral devices.
Figure 7 240 VAC Power
Wiring.
Fuse
10
Fuse
12
13
240 VAC
L1
L2
Earth Ground
Sensor Installation Guidelines
We suggest you mount the sensor at a location in your process or system where it
reads an average temperature. Put the sensor as near as possible to the material
or space you want to control. The sensor should be thermally insulated from the
sensor mounting.
WATLOW Series 942 User's Manual
8
Install and Wire, Chapter 2
Thermocouple Input
Input Wiring
Model # 942A -
942A -
You must use an isolated or ungrounded thermocouple, if an external device with a nonisolated circuit common is connected to the 4-20mA or 0 - 5VDC output.
Extension wire for thermocouples must be of the same alloy as the thermocouple itself to
limit errors.
1 _ _ _ - _ 000 942A - 3 _ _ _ - _ 000
2 _ _ _ - _ 000 942A - 4 _ _ _ - _ 000
+
7
9
-
Figure 8 Thermocouple
Input Wiring.
RTD, 2 or 3 Wire
Model # 942A -
Long lead lengths create electrical resistance. There will be approximately +2°C input error
for every 1Ω of lead length resistance, when using a two wire RTD. The resistance, when
added to the resistance of the RTD element, will result in erroneous input to the instrument.
To overcome this problem, use a three wire RTD sensor, which compensates for lead length
resistance. When extension wire is used for a three wire RTD, all three extension wires
must have the same electrical resistance. (i.e. same gauge, copper stranded).
2 _ _ _ - _ 000 942A - 3 _ _ _ - _ 000
Jumper #5 to #6
for 2-Wire RTD
4
5
6
4
5
6
Figure 9 2 or 3 wire RTD
Input Wiring.
Install and Wire, Chapter 2 WATLOW Series 942 User's Manual
9
Input Wiring
Figure 10 0 - 5VDC Process
Input Wiring.
When using a process input such as 0 - 5VDC or 4 - 20mA, the rL and rH settings scale the
display to match the measured range of the process signal.
An example of this is: A pressure transducer operates over a range of 0 - 300 PSI, delivering
a 4 - 20mA output signal for this range. By setting rL = 0 and rH = 300, the Series 942 now
displays a direct reading of pressure.
0 - 5VDC Process Input
Model # 942A - 2 _ _ _ - _ 000 942A - 3 _ _ _ - _ 000
+
1
V
2
3
-
DC
NOTE:
When using a
0 - 5VDC process
input, the input
impedance is
100KΩ.
Figure 11 4 - 20mA Process
Input Wiring.
4 - 20mA Process Input
Model # 942A - 2 _ _ _ - _ 000 942A - 3 _ _ _ - _ 000
A jumper must be
installed between
Terminals #2 and 3.
1
2
3
+
DC
I
-
NOTE:
When using a
4 - 20mA process
input, the input
impedance is 249Ω.
WATLOW Series 942 User's Manual
10
Install and Wire, Chapter 2
Solid State Relay With Contact Suppression, Output 1
Model # 942A - _ B _ _ - _ 000
Solid State Relay, Form A, 0.5 Amp
External
N.O.
17
COM.
18
Solid State Relay With Contact Suppression
Watlow's solid state relay changes state at zero volts, which is "zero-cross switching." They
are also optically isolated, which means the output circuitry is energized by infrared light
striking a photosensitive device. This results in a virtual absence of electrically generated
noise, and provides electrical isolation between the input and output. For use in switching
mercury relays or small AC loads. Off state impedance is 20KΩ minimum.
Load
Fuse
L2
L1
Output 1 Wiring
Figure 12 Solid State Relay
With Contact
Suppression,
Output 1 Wiring.
NOTE:
This output is supplied with an arc
suppression snubber across the output terminals. High
impedance loads
may remain energized even though
the output device is
turned OFF.
Switched DC Output (Open Collector), Output 1
Model # 942A - _ C _ _ - _ 000
Switched DC, Open Collector, Non-Isolated
16
17
External
+
Load
Logic
Switch
Switched DC
Watlow's solid state switch is a low current DC output (open collector) used to switch an
external power switching device such as an SSR or an electromechanical relay. The input
specifications of the power switching device must match those listed for the SS switch
output. The power switching device must provide isolation between the SS switch output
and load power since the SS switch output is a non-isolated output. Minimum load resistance is 500Ω. Available current is 22mA maximum. Typical voltage drop across a 1KΩ
load is 12 to 19 volts.
-
+
Figure 13 Switched DC
(Open Collector),
Output 1 Wiring.
Install and Wire, Chapter 2 WATLOW Series 942 User's Manual
11
Output 1 Wiring
Figure 14 6 Amp Mechanical
Relay, Output 1
Wiring.
NOTE:
This output is supplied with an arc
suppression snubber across the output terminals. High
impedance loads
may remain energized even though
the output device is
turned OFF.
Mechanical Relay, 6 Amp, Form C, Output 1
Model # 942A - _ D _ _ - _ 000
Mechanical Relay, Form C, 6 Amp
COM.
16
N.O.
17
18
N.C.
Mechanical Relay
The electromechanical relay is an electrical and mechanical device with moving parts.
When power is applied to the relay solenoid, contact closure is created through movement
of the "common" contact of the relay.
Off state impedance is 20KΩ minimum.
Fuse
External
Load
L1
L2
Figure 15 Process, 0 - 10VDC,
Output 1 Wiring.
Process, 0 - 10VDC, Output 1
Model # 942A - _ E _ _ - _ 000
Process, 0-10VDC, Non-Isolated
16
17
-
+
External
Load
-
+
Process Output
Proportional value determined by the control to balance the sensor input and set point. This
value will fall between 0 - 10VDC depending on the thermal characteristics of the system.
Load impedance is 10KΩ minimum.
WATLOW Series 942 User's Manual
12
Install and Wire, Chapter 2
Process, 4 - 20mA, Output 1
Output 1 Wiring
Model # 942A - _
Process, 4-20 mA, Non-Isolated
Process Output
Proportional value determined by the control to balance the sensor input and set point. This
value will fall between 4 - 20mA depending on the thermal characteristics of the system.
Load impedance is 600
F _ _ - _ 000
Ω maximum.
+
I
DC
-
17
18
+
External
-
Load
Figure 16 Process, 4 - 20mA,
Output 1 Wiring.
Process, 0 - 20mA, Output 1
Model # 942A - _
Process, 0-20 mA, Non-Isolated
Process Output
Proportional value determined by the control to balance the sensor input and set point. This
value will fall between 0 - 20mA depending on the thermal characteristics of the system.
Load impedance is 600
G _ _ - _ 000
Ω maximum.
-
I
DC
+
16
17
External
+
Load
Figure 17 Process, 0 - 20mA,
Output 1 Wiring.
Install and Wire, Chapter 2 WATLOW Series 942 User's Manual
13
Output 1 Wiring
Figure 18 Process, 0 - 5VDC,
Output 1 Wiring.
Process, 0 - 5VDC, Output 1
Model # 942A - _ H _ _ - _ 000
Process, 0-5VDC, Non-Isolated
17
++
-
Process Output
Proportional value determined by the control to balance the sensor input and set point. This
value will fall between 0 - 5VDC depending on the thermal characteristics of the system.
Load impedance is 10KΩ minimum.
18
External
-
Load
Figure 19 Solid State Relay
Without Contact
Suppression, Output
1 Wiring.
Solid State Relay Without Contact Suppression, Output 1
Model # 942A - _ K _ _ - _ 000
Solid State Relay, Form A, 0.5 Amp
External
N.O.
17
COM.
18
Solid State Relay Without Contact Suppression
Watlow's solid state relay changes state at zero volts, which is "zero-cross switching." They
are also optically isolated, which means the output circuitry is energized by infrared light
striking a photosensitive device. This results in a virtual absence of electrically generated
noise, plus output to input electrical isolation. Off state impedance is nearly infinite and
should be used to switch high impedance non-inductive loads.
Load
Fuse
L2
L1
WATLOW Series 942 User's Manual
14
Install and Wire, Chapter 2
Solid State Relay With Contact Suppression, Output 2
Model # 942A - _ _ B _ - _ 000
Solid State Relay, Form A, 0.5 Amp
N.O.
14
15
COM.
Solid State Relay With Contact Suppression
Watlow's solid state relay changes state at zero volts, which is "zero-cross switching." They
are also optically isolated, which means the output circuitry is energized by infrared light
striking a photosensitive device. This results in a virtual absence of electrically generated
noise, and provides electrical isolation between the input and output. For use in switching
mercury relays or small AC loads. Off state impedance is 20K
Ω minimum.
Fuse
External
Load
L1
L2
L2
L1
Output 2 Wiring
Figure 20 Solid State Relay
With Contact
Suppression,
Output 2 Wiring.
NOTE:
This output is supplied with an arc
suppression snubber across the output terminals. High
impedance loads
may remain energized even though
the output device is
turned OFF.
Switched DC Output (Open Collector), Output 2
Model # 942A - _ _ C _ - _ 000
Switched DC, Open Collector, Non-Isolated
+
Logic
Switch
Switched DC
Watlow's solid state switch is a low current DC output (open collector) used to switch an
external power switching device such as a SSR or an electromechanical relay. The input
specifications of the power switching device must match those listed for the S.S. switch
output. The power switching device must provide isolation between the S.S. switch output
and load power since the S.S. switch output is a non-isolated output. Minimum load
resistance is 500Ω. Available current is 9mA minimum and 22mA maximum.
-
14
15
+
External
-
Load
Figure 21 Switched DC Output
(Open Collector),
Output 2 Wiring.
Install and Wire, Chapter 2 WATLOW Series 942 User's Manual
15
Output 2 Wiring
Figure 22 6 Amp Mechanical
Relay, Output 2
Wiring.
Mechanical Relay, 6 Amp, Form A, Output 2
Model # 942A - _ _ D _ - _ 000
Mechanical Relay, Form A, 6 Amp
14
15
N.O.
COM.
External
Load
Fuse
L2
L1
L1
L2
NOTE:
This output is supplied with an arc
suppression snubber across the output terminals. High
impedance loads
may remain energized even though
the output device is
turned OFF.
Figure 23 Solid State Relay
Without Contact
Suppression,
Output 2 Wiring.
Mechanical Relay
The electromechanical relay is an electrical and mechanical device with moving parts.
When power is applied to the relay solenoid, contact closure is created through movement
of the "common" contact of the relay. Off state impedance is 20K
Ω minimum.
Solid State Relay Without Contact Suppression, Output 2
Model # 942A - _ _ K _ - _ 000
Solid State Relay, Form A, 0.5 Amp
14
15
N.O.
COM.
Fuse
External
Load
L1
L2
L1
L2
WATLOW Series 942 User's Manual
16
Solid State Relay Without Contact Suppression
Watlow's solid state relays change state at zero volts, which is "zero-cross switching." They
are also optically isolated, which means the output circuitry is energized by infrared light
striking a photosensitive device. This results in virtual absence of electrically generated
noise, while providing output to input electrical isolation. Off state impedance is nearly
infinite and should be used to switch high impedance non-inductive loads.
Install and Wire, Chapter 2
For more information on alarms, alarm jumper selection and events,
see Chapter 6.
Mechanical Relay
The electromechanical relay is an electrical and mechanical device with moving parts.
When power is applied to the relay solenoid, contact closure is created through movement of
the "common" contact of the relay. Off state impedance is 20K
Ω minimum.
Mechanical Relay, 6 Amp, Single Form A or B, Auxiliary Output
Model # 942A- _ _ _ 1 - _ 000
Auxiliary Wiring
Figure 24 Auxiliary Option 1
Wiring.
Mechanical Relay, Form A or B, 6 Amp
Output #3
26
27
Load
L1
L2
Mechanical Relay, 6 Amp, Dual Form A or B, Auxiliary Output
Model # 942A- _ _ _ 2 - _ 000
Mechanical Relay, Form A or B, 6 Amp
Fuse
Output #4
Output #3
24
25
26
27
Load
Fuse
Load
L1
L2
L1
L2
NOTE:
This output is supplied with an arc
suppression snubber across the output terminals. High
impedance loads
may remain energized even though
the output device is
turned OFF.
Figure 25 Auxiliary Option 2
Wiring.
Install and Wire, Chapter 2 WATLOW Series 942 User's Manual
17
Auxiliary Wiring
Mechanical Relay
The electromechanical relay is an electrical and mechanical device with moving parts.
When power is applied to the relay solenoid, contact closure is created through movement of
the "common" contact of the relay.
Mechanical Relay, 6 Amp, Form A or B/0 - 5VDC Retransmit
Model # 942A- _ _ _ 3 - _ 000
Figure 26 Auxiliary Option 3
Wiring.
NOTE:
This output is supplied with an arc
suppression snubber across the output terminals. High
impedance loads
may remain energized even though
the output device is
turned OFF.
Process, 0-5VDC, Non-Isolated
24
25
26
27
+
Fuse
Load
External
Load
Mechanical Relay, Form A or B, 6 Amp
Output #4
Output #3
Load impedance 10K
Ω mimimum.
-
+
Mechanical Relay, 6 Amp, Form A or B/4 - 20mA Retransmit
Model # 942A- _ _ _ 4 - _ 000
L1
L2
Figure 27 Auxiliary Option 4
Wiring.
WATLOW Series 942 User's Manual
18
Process, 4-20 mA, Non-Isolated
Mechanical Relay, Form A or B, 6 Amp
Output #4
Output #3
Load impedance 600Ω maximum.
I
DC
+
External
-
-
+
24
25
26
27
Fuse
Load
Load
L1
L2
Install and Wire, Chapter 2
Retransmit Output
When using a retransmit output such as 0 - 5VDC or 4 - 20mA, the rL and rH settings scale
the range of the retransmit output.
An example of this is: By setting rL = 0, rH = 1000 and Ot4 = PrOC a process value of 500
will result in a retransmitted signal of 2.5VDC or 12mA.
0 - 5VDC Retransmit, Auxiliary Output
Model # 942A- _ _ _ 5 - _ 000
Process, 0-5VDC non-isolated
Auxiliary Wiring
Figure 28 Auxiliary Option 5
Wiring.
-
+
Load impedance 10KΩ mimimum.
4 - 20mA Retransmit, Auxiliary Output
Model # 942A- _ _ _ 6 - _ 000
Process, 4-20 mA, Non-Isolated
24
25
External
+
Load
Figure 29 Auxiliary Option 6
Wiring.
-
IDC
+
Load impedance 600
Install and Wire, Chapter 2 WATLOW Series 942 User's Manual
Ω maximum
24
25
+
-
External
Load
19
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