ICS Triplex ICS Regent Analogue Output Modules Reference Manual

ICS Regent
®
PD-6025
Analog Output Modules
4 to 20 mA
(T3470A)
Issue 1, March, 06
Analog output modules provide 4 to 20 mA current outputs for
a maximum of eight user loads per module. The module's
triplicated I/O Safetybus interface ensures that no Regent
system failure will inadvertently affect the output signal, and
that no failure in the module can affect the operation of the
Regent system or other I/O modules in the system.
Features
·
Eight 4 to 20 mA output circuits.
·
High resolution 12-bit D/A converter per output.
·
Hot-replaceable.
·
Automatic testing of triplicate I/O Safetybus circuits and many
simplex logic circuits.
·
Front panel indicators on each module show active/fault and
shutdown status.
·
2500 volt minimum electrical isolation between field and logic
circuits.
·
TÜV certified, Risk Class 5, non-interfering.
Module Operation
A block diagram of the analog output module is shown in
Figure 1.
The processor modules send triplicated write data commands
to the output module over the I/O Safetybus. The processors’
addressing data and data write commands are voted by the
module (preventing I/O Safetybus failures upstream from the
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module from affecting module operation). The voted result is
then passed to the I/O bus interface logic.
The voted output data from the I/O bus interface logic is then
used to drive individual digital-to-analog (D/A) converters per
output channel. The field-side D/A output circuits are
optically isolated from the I/O bus interface logic circuits and
receive power from the external power supply.
Each D/A output circuit provides a 4 to 20 mA output current
corresponding to analog output values ranging from 0 to
4095. The analog output circuits are capable of driving
external load devices up to 500 Ohms.
Figure 1. Block Diagram of Analog Output Module.
Testing and Diagnostics
Each module’s voter circuits are periodically tested by the
processor modules. Discrepant data are sent through one of
three legs of the I/O Safetybus to determine whether the
module’s voter is able to outvote the incorrect data. A failure
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to return the correct majority-voted result to the processors
produces an I/O module error indication at the processor
modules and a module fault indication at the I/O module.
Each type of module has a unique identification code that is
read by the controller. This code lets the controller know
which type of module is installed in each I/O chassis slot and
how to address that module and its points specifically. If a
module is removed, or is replaced with a module of a different
type, the processor modules will indicate an I/O module error.
Loopback logic tests periodically write data to the module and
then read it back to determine whether the module’s I/O bus
interface logic is functioning correctly.
Whenever a module fault is detected, there will be an I/O
module fault indication at the controller, the controller's fault
relay contacts are actuated, and fault indication will appear
on the module.
Front Panel Indicators
The analog output module is shown in Figure 2. The front
panel contains active, fault, and shutdown indicators.
Active and Fault Status Indicators
These green and red LEDs indicate the overall health of the
module. During normal operation the green ACTIVE
indicator flashes at the controller's scan rate. If a module
fault occurs the red FAULT indicator turns on and the green
ACTIVE indicator turns off.
Note: The module will indicate a FAULT if the field power is not
applied.
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Figure 2. Analog Output Module.
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Shutdown Indicator
Upon loss of communications with the controller, output
modules enter either a shutdown or hold fault mode. If the I/O
unit is set to shutdown, the red SHUTDOWN indicator will
turn on when communications with the controller are lost. If
the I/O unit is set to hold, the SHUTDOWN indicator will
always be off (see page 8, Fault Mode Jumper).
Note: When the module is installed in the I/O chassis or when logic
power (from the I/O power supply modules) is first applied to
the module, it will be in the shutdown mode until the first
output scan, regardless of the fault mode jumper settings.
Also, removing two I/O transceiver modules, two I/O power
supply modules, or two power legs will cause the module to be
in the shutdown mode.
Application
Simplex Configuration
Analog output modules provide a suitable interface to noncritical load devices. These non-critical devices typically
include analog display meters, valve positioners and analog
signal repeats to other electronic equipment. Although much
of the circuitry of the analog output module is automatically
tested, some of the logic circuits and the field-side D/A circuits
are simplex and non-tested. This simplex configuration is
shown in Figure 3.
Figure 3. Simplex Analog Output Configuration.
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For high integrity applications requiring fail-safe or fault
tolerant analog outputs, guarded analog outputs should be
used.
Field Wiring
Field wiring terminal blocks on the I/O chassis are used to
connect an external 24 VDC power source and analog loads to
the module. The terminal blocks are located directly above
and below the slot where the module is installed. Each
terminal block consists of ten #6 wire clamp screw terminals
capable of holding two 12 AWG wires. Figure 4 shows the
proper field wiring connections for the analog output module.
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Figure 4. Module Wiring.
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Fault Mode Jumper
The fault mode jumper is located behind the ID switch cover
in the lower left-hand corner of each I/O chassis. The position
of the fault mode jumper determines the module's response to
system level faults. The fault mode jumper’s position will
cause all output modules in the I/O chassis to either shutdown
(turn off all outputs) or to hold (hold the last state) after a
system level failure occurs. An example of a system level
failure is the failure of two processor modules.
Important! When the analog output module is in the shutdown mode,
analog output signals are at 0 mA (not 4 mA).
Keying
The I/O chassis can be physically keyed to prevent accidental
damage caused by inserting a module into a slot wired for a
different module type. Figure 5 illustrates how the slot keys
are installed on the I/O chassis slot field wiring connectors.
The slot key positions for the analog output module are listed
in Table 1.
Table 1. Slot Key Positions.
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Module
Upper
Connector
Lower
Connector
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Figure 5. Installing Slot Keys.
Configuration
Each output module is configured using the WINTERPRET I/O
Configuration Editor. In the editor you will perform the three
steps described below to configure the output module.
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1) Set the Module Type:
Position the cursor on the module slot you wish to define.
Choose Set Module Type from the Edit Menu and select
the appropriate analog output module from the list.
2) Edit the Module Definition:
Choose Edit Module Definition from the Edit Menu. A
dialog box will open where you can define the analog
output point definitions.
Figure 6. Analog Output Module Definition.
3) Edit each point:
Choose Edit from the Module Definition dialog box to
define a name and description for each output point. In
the Analog Output Point dialog, enter names and values
for the configuration fields as described below.
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Figure 7. Defining an Analog Output Point.
Name
Also called the tag name, this is the name used in the
application program to reference the output point. The name
can be up to 12 characters long.
Description
This 40-character field provides a place to describe the output
point definition. The description is used to help document
your system (it does not affect application program operation).
Comm Protect
Marking the Comm Protect check box protects the point from
changes by communications functions such as data write,
forcing, and load initial value when Comm Protect is enabled.
Initial Value
The initial value for the output is loaded to the Regent when
you load the I/O configuration and also when you load the
application program that controls the output.
Final Value
The final value for the output is loaded to the Regent when
the application program that controls the output is deleted.
Unless special circumstances exist, you should always enter
zero, so that the output is turned off when you delete the
application program that controls it.
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Programming
Outputs are controlled by writing application programs that
solve for output values. For example, placing an output tag
name in the result field of a math element in ladder logic will
set the analog output to the value calculated by the math
element. Note that the data range for analog outputs is 0 to
4095 corresponding to the output current rage of 4 to 20 mA.
Often you may choose to write analog control logic using an
engineering unit number range other than 0 to 4095 to
simplify the creation and interpretation of the control logic. If
you do so you should use the analog scaling function block to
“unscale” your calculated value to the 0 to 4095 range
required for the analog output. An example of an analog
scaling entry for analog outputs is shown in Figure 8.
Figure 8. Unscaling an Analog Output.
This example implies that some other control logic solves a
value for the shared register “AO1_ENG_VAL” which ranges
from 0 to 10,000 (the low and high values). The analog
scaling entry shown in the example then converts the
engineering unit value to the analog output range of 0 to
4095, storing the converted value in the analog output “AO1”.
By using an engineering unit range of 0 to 10,000 for your
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control logic, you maintain the full resolution of the analog
output (1 part in 4096) and have a convenient engineering
range that represents 0.00 to 100.00% (the two decimal places
are implied).
Maintenance
There are no user replaceable parts inside the analog output
module. Re-calibration is recommended once per year, in
order to maintain the rated accuracy of the analog output
signals over an extended period of time. The following
procedure describes the equipment and steps necessary to
calibrate the analog output module.
Calibration Procedure
Equipment Required
· A 5½-digit voltmeter.
·
Eight 250 ohm, 0.005%, 5 ppm/°C resistors to convert the
eight output signals from a current to a voltage.
·
Potentiometer adjustment tool.
·
Phillips screwdriver
·
I/O module extender, catalog number T3322.
·
PC running the WINTERPRET software, used to force the
analog output channels to the specific values for
calibration.
Calibration Preparation
The module must be calibrated while connected to an I/O
chassis of an operational Regent system.
Important! During calibration, the analog output module will be
disconnected from the actual controlled field devices.
Appropriate precautions should be taken to ensure that the
disconnection of the control signals does not pose a safety risk
to plant personnel or process equipment.
There are Offset and Gain potentiometers for each analog
output channel. These potentiometers are located on a circuit
board inside the module's protective clamshell housing (see
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Figure 9). During the calibration steps you will remove the
printed circuit board from the housing in order to access these
potentiometers for adjustment.
Figure 9. Analog Output Module Calibration Potentiometer
Locations.
The I/O extender module has jumper posts that allow you to
connect or disconnect the I/O slot field wiring on the I/O
chassis to the printed circuit board plugged into the I/O
extender. During the calibration steps you will remove any
jumpers installed on these posts in order to connect the
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precision load resistors to the analog outputs. Figure 10
shows the jumper posts to which you should connect the
precision resistors for each analog output channel.
Figure 10. I/O Extender Connections for Analog Output Calibration.
Important! Within each pair of jumper posts, make sure that you connect
the resistors to the jumper posts nearest the front of the I/O
extender. Do not make any connections to the jumper posts
nearest the I/O chassis backplane — these connect to the
actual field wiring attached to the I/O slot terminals on the I/O
chassis.
Calibration Steps
1. Remove the module to be calibrated from the I/O chassis.
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2. Install the I/O extender module into the slot from which
the module was removed.
3. Remove the jumpers (if installed) labeled CH1 through
CH16 from the I/O extender module.
4. Connect the eight precision resistors to the I/O extender
jumper posts as shown in Figure 10. Use test clips as
required to make the connections.
5. Remove the four screws on one side of the module and
remove the printed circuit board from the module
clamshell housing.
6. Install the printed circuit board into the I/O extender
module. Allow the board to warm up for approximately one
minute.
7. Using the forcing functions of WINTERPRET, force all of the
eight analog outputs to zero. Refer to the Regent User’s
Guide for more details about the forcing functions. Wait
approximately one minute after forcing the outputs to
allow them to stabilize.
8. Adjust the eight Offset potentiometers to read +1.0000 V
(± 0.0002 V) across each of the precision resistors. Connect
the voltmeter across the resistor leads to measure the
voltage.
9. Force all eight of the outputs to 4095. Wait approximately
one minute after forcing the outputs to allow them to
stabilize.
10. Adjust the eight Gain potentiometers to read +4.9990 V
(± 0.0002 V) across each of the precision resistors.
11. Repeat steps 7 through 10 and readjust the Offset and
Gain potentiometers if necessary until the Offset and Gain
voltages are within the stated limits.
12. Force all eight of the outputs to 2048. Wait approximately
one minute after forcing the outputs to allow them to
stabilize.
13. Verify that the output voltages read +3.0000 V (± 0.0020
V) across each of the precision resistors. If the Offset and
Gain adjustments are within the limits stated in steps 8
and 10 above, but this midvalue point is not, return the
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analog output module to the factory for repair or
replacement.
14. Calibration is complete. Unplug the printed circuit board
from the I/O extender module and replace it in its
clamshell housing. Remove all forcing of the analog
outputs from the force table using WINTERPRET. Remove
the I/O extender module from the I/O chassis and reinstall
the calibrated module in the I/O chassis.
The module’s red Fault indicator will be on until you
perform a voted reset by pressing the Reset buttons on two
of the Regent processor modules. After the voted reset is
complete, the module’s green Active indicator should turn
on.
Safety Considerations
The analog output module is TÜV certified as non-interfering,
and can be used in a safety system for simplex non-safety
critical outputs.
Specifications
Safetybus Power
0.5 load units
Number of Outputs
Eight
External Power
Voltage:
Current:
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24 VDC ±5%
0.5 amps, maximum
Output Range
4 to 20 mA
Data Range
0 to 4095
Resolution
12-bit (1 in 4096)
Accuracy
0.1% of full scale @ 25° C
Drift
±50 ppm/°C
Load Resistance
0 to 500 ohms
Isolation
2500 volts minimum (field
wiring to control logic)
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Heat Dissipation
10 Watts, 33 BTUs/hour
Operating Temperature
0° to 60° C
(32° to 140° F)
Storage Temperature
-40° to 85° C
(-40° to 185° F)
Operating Humidity
0 to 95% relative humidity,
non-condensing
Vibration
10 to 55 Hz:
±0.15mm
Shock
Operating:
15 g, ½ sine wave, 11 msec
Electromagnetic
Interference
•
•
IEC 801 Part 2 - Electrostatic
Discharges
IEC 801 Part 3 - Radiated
Electromagnetic Fields
Safety
Level 3: Contact discharge of
6 kV
Level 3: 10 V/M, 27 MHz 500 MHz
Certified to DIN V VDE
0801 (non-interfering) and
designed to meet UL 508 and
CSA 22.2, No. 142-M1981
Dimensions
Height:
Width:
Depth:
Weight
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12.6" (320 mm)
1.27" (32 mm)
10.12" (257 mm)
3.5 lbs (1.6 kg)
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