Output Holder for MOD 30ML™ Application Guide
Description and Application of
1726F Output Holder
MicroMod Automation, Inc.
The Company
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MOD 30 and MOD 30ML are trademarks of MicroMod Automation, Inc.
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Using The Output Holder With MOD 30ML
Contents
CONTENTS
INTRODUCTION ...........................................................................................................................................1
SCOPE ..........................................................................................................................................................1
FIRMWARE VERSIONS................................................................................................................................1
RELATED INFORMATION............................................................................................................................1
TECHNICAL SPECIFICATIONS....................................................................................................................2
Output Holder Panel 1725F........................................................................................................................2
Output Holder Card 1726F.........................................................................................................................2
OUTPUT HOLDER PURPOSE .....................................................................................................................3
GENERAL......................................................................................................................................................3
1726F THEORY OF OPERATION ................................................................................................................3
WIRING & CONNECTIONS...........................................................................................................................5
MOD 30ML APPLICATION...........................................................................................................................7
GENERAL......................................................................................................................................................7
LOADING THE COMPOUND........................................................................................................................8
OUTPUT HOLDER COMPOUND THEORY OF OPERATION ...................................................................10
1. B
ASIC FUNCTIONAL BLOCK DIAGRAM
2. G
ENERIC OUTPUT HOLDER CONNECTION DIAGRAM
3. O
UTPUT HOLDER COMPOUND
1. O
UTPUT HOLDER CABLE WIRE DEFINITIONS
2. B
LOCK EXECUTION ORDER
..........................................................................................................................9
...........................................................................................................4
.....................................................................................................................7
FIGURES
......................................................................................5
TABLES
................................................................................................6
i
Using The Output Holder With MOD 30ML
Contents
ii
SCOPE
This book is one of a series that discusses the application of MOD 30ML™ to commonly
encountered process control loops. This book discusses use of the 1726F Output Holder
with the MOD 30ML controller.
The primary purpose of this document is to identify the function of the output holder, how
to connect an output holder card to the MOD 30ML Controller and how the output holder
compound strategy interfaces with the hardware. Connection diagrams and list are
supplied to show how the 1726F Output Holder is connected to the MOD 30ML.
FIRMWARE VERSIONS
The process examples in this book are applicable to all firmware versions of the
instruments.
Using The Output Holder With MOD 30ML
Introduction
INTRODUCTION
RELATED INFORMATION
Before actually configuring an instrument, you should be familiar with the information
contained in the following publications:
• IB-1800R-OPR - MOD 30ML Multiloop Controller Operation Guide
• IB-1800R-APP - MOD 30ML Functions Data Base Reference Guide
• IB-1800-INS - MOD 30ML Multiloop Controller Installation Guide
• IB-1800-M30 - MOD 30ML Multiloop Controller Replacement for MOD 30 Instruments
Installation Guide
1
Using The Output Holder With MOD 30ML
Introduction
TECHNICAL SPECIFICATIONS
Output Holder Panel 1725F
Width - 19-inches (483-mm) Weight - 4 lbs. 9-1/2 oz. (2.08 kg) max.
Depth - 6-inches (153-mm) Panel Capacity - 6 Output Holders
Height - 3-1/2-inches (89-mm)
Output Holder Card 1726F
Analog Input
Span (0 to 100%) 4 to 20mA
Lower Limit 2.72mA
Upper Limit 21.28mA
Analog Output (I OUT)
Span (0 to 100%) 4 to 20mA
Lower Limit (-8%) 2.72mA
Upper Limit (+ 108%) 21.2BmA
Current Return (I RETURN)
Span (0 to 100%) 1 to 5mA
Lower Limit (- 8%) 0.68mA
Upper Limit (+ 108%) 5.32mA
Calibrated Accuracy (% of span)
I OUT, Run Mode (with respect to analog input) ± 0.5% max.
I OUT, Hold Mode (with respect to run mode analog input) ± 1.0% max.
I RETURN, Run Mode (with respect to analog input span) ± 0.7% max.
I RETURN, Hold Mode (with respect to run mode analog input span) ± 1.2% max.
Input/Output Characteristics
Analog Input Resistance 250 ohms typical
Analog Output (I OUT) Resistance 50k ohms min.
Open Circuit Output Voltage 24V dc max.
Output Ripple (100kHz) 1 % peak
Analog Output Load Capability
Resistance 800 ohms max.
Capacitance 10 uF max.
Inductance 10 H max.
Power Supply Requirements
Normal Operating Range 23V dc to 28V dc
Allowable Operating Range 16V dc to 28V dc
Allowable Ripple 1.0V P-P
Maximum Current 85mA dc
Environmental Requirements
Operating Temperature + 41°F (+ 5°C) to 122°F(50°C)
Physical Characteristics
Width 5-1/2-in. (140-mm)
Depth 4-3/8-in. (111-mm)
Height 13/16-in. (21-mm)
Weight 0.2 lbs. (85.5g)
2
GENERAL
Using The Output Holder With MOD 30ML
Output Holder Purpose
OUTPUT HOLDER PURPOSE
For safe operation some processes require that valve position be maintained above a
closed position even when a controller might be removed for service or replacement. The
Output Holders task is to identify a controller output fault and to maintain the last good
value to the field control device for safe operation. When the controllers output signal to
the output holder is restored and again valid the output holder must return control of the
field device to the controller. Under normal operation i.e.; the controllers output is good,
the controllers output is passed through the output holder to the field control device
unaffected.
From the example above, it can be understood that if an output holder has taken control
of a field device signal due to a controller being removed, when the controller is replaced
there could be a “bump” to the control valve if the controllers output is not first brought
equal to or “synchronized” to that of the output holder. To prevent this bump from
happening the controller must first be aware of the output holders output value and make
its output equal to it before the controller can turn its output on.
The MOD 30ML Output Holder Compound strategy demonstrated in this document is
designed to identify that an output holder exists in the controllers output circuit and how to
synchronize its output value to that of the output holders output prior to turning the
controllers output on.
The 1726F Output Holder card can be used on as many as three MOD 30ML control
loops.
1726F THEORY OF OPERATION
Figure 1 shows a block diagram of the 1726F Output Holder operation.
The controllers output is fed into the output holder as a 4-20 milliamp signal where it is
converted to a 1-5 Vdc value by the I/V Converter circuit. This signal is then fed to the
Analog MUX, Input Monitor and Input Conditioner circuits.
The Input Monitor circuit compares the input signal to a low limit of -8%. The result of this
block is a “Run/Hold” selection signal which is used by the Analog MUX circuit to select
the controllers output or hold value as the value to be sent to the field.
The Up/Down circuit compares the controllers output as conditioned by the Input
Conditioner circuit to that of the hold value. Its resultant signal causes the Up/Down
Counter to either increment or decrement its count based on whether the controllers input
is higher or lower than that of the hold value. The goal is maintain the hold value equal to
that of the controller output during normal operation.
The Clock Control circuit gates the Clock signal through to the clock input of the Up/Down
Counter. When the Analog MUX selects the hold value as the value to be sent to the field
then the Clock Control circuit blocks the clock pulses from reaching the Up/Down
Counter, thereby causing the hold value to become steady. While the controllers output
3
Using The Output Holder With MOD 30ML
Output Holder Purpose
value is being sent to the field the Clock Control permits the clock pulses to reach the D/A
Converter causing it to float with the controllers output value.
The Up/Down Counter counts clock pulses and either increments or decrements the
count value at its parallel output.
The D/A Converter receives the counters value and converts it to a 1-5 Vdc signal. This
value is in turn sent to the Analog MUX circuit through the Output Conditioning circuit.
The V/I Converter circuit converts the 1-5 Vdc signal to 4-20 milliamp output and 1-5
milliamp Return signals to be used by the field and controller respectively.
The Return line is sent back to the controller and is used to synchronize its output to that
of the output holder in order to cause bumpless transfer when a controller is first brought
on line.
The Sense line is generated on the output holder card and is nothing more than a dc
common. This signal is sent back to the controller and is used to determine if an output
holder card is present.
4-20 mA
I/V
Converter
Input
Monitor
-8%
Input
Conditioner
75 MHz
Clock
Analog
MUX
Run/Hold
V out
Up/Down
Control
Clock
Control
Enabl e/Disable
Hold Value
V/I
Converter
Up/Down
Counter
Clk
Bit 10
Bit 0
Figure 1. Basic Functional Block Diagram
Return
Output
Sense
1-5mA
4-20mA
D/A
Converter
Output
Conditioning
Gnd
4
WIRING & CONNECTIONS
Figure 2 provides a generic reference as to the signal paths between the controller and
the 1726F Output Holder card. Table 1 provides a complete output holder wire color and
signal listing as viewed from the 1751FZ output holder cable. This is required to provide
detailed wire connection for multiple output holder applications to a single controller.
Using The Output Holder With MOD 30ML
Output Holder Purpose
Process Input
4-20 mA
To Process
MOD 30M L
Contro ller
Controllers
Output
I Return
O. H. Sense
4-20 mA
1726F
Output Ho lder
Figure 2. Generic Output Holder Connection Diagram
For the Sense and Return signals to be received by the MOD 30ML Controller two inputs
are required. The input types are:
• non 2-wire current input
• digital input (2006AZ)
The current input is used for the Return signal and is configured for 1-5 milliamps. The
2006AZ digital input module is used to bring in the Sense signal.
The exact wire connections for a particular MOD 30ML Controller output holder
application depend on how many outputs are being held and where the Sense and Return
I/O points for each loop are located on the controller. If Built In Analog Input #2 is not
being used for control it may be set up for 1-5 milliamps non 2-wire and used to bring in
the Return signal. In all cases the Sense signal will require the installation of a 2006AZ
digital input module.
5
Using The Output Holder With MOD 30ML
Output Holder Purpose
Table 1. Output Holder Cable Wire Definitions
Twisted Pair # Colors P1 Conn. Pin # Connection Note
1 wht 1 O.H.#3 sense
blu 19 O.H.#3 return
2 wht 2 O.H.#3 input
org 20 O.H.#3 output
3 wht 3 O.H.#3 24Vdc
grn 21 O.H.#3 ckt. common 1
4 wht 4 O.H.#2 sense
brn 22 O.H.#2 return
5 wht 5 O.H.#2 input
slate 23 O.H.#2 output
6 red 6 O.H.#2 24Vdc
blu 24 O.H.#2 ckt. common 1
7 red 7 O.H.#1 sense
org 25 O.H.#1 return
8 red 8 O.H.#1 input
grn 26 O.H.#1 output
9 red 9 O.H.#1 24Vdc
brn 27 O.H.#1 ckt. common 1
10 red 10 O.H.#6 sense
slate 28 O.H.#6 return
11 blk 11 O.H.#6 input
blu 29 O.H.#6 output
12 blk 12 O.H.#6 24Vdc
org 30 O.H.#6 ckt. common 1
13 blk 13 O.H.#5 sense
grn 31 O.H.#5 return
14 blk 14 O.H.#5 input
brn 32 O.H.#5 output
15 blk 15 O.H.#5 24Vdc
slate 33 O.H.#5 ckt. common 1
16 yel 16 O.H.#4 sense
blu 34 O.H.#4 return
17 yel 17 O.H.#4 input
org 35 O.H.#4 output
18 yel 18 O.H.#4 24Vdc
grn 36 O.H.#4 ckt. common 1
Note:
1. Be sure this is common with the controllers DC common.
6
GENERAL
Using The Output Holder With MOD 30ML
MOD 30ML Application
MOD 30ML APPLICATION
Figure 3 shows a block diagram of the output holder compound strategy. This strategy
contains the PID, display and I/O for one loop. When using this compound you will be
required to complete a few strategy changes to make it fit your application. These
changes are outlined in Loading the Compound.
The purpose of the output holder compound is to cause the control loop output to
synchronize its output to that of the output holder before turning its field output on. This
will in turn cause a bumpless transfer. This happens only when the controller first
initializes at power up.
Figure 3. Output Holder Compound
7
Using The Output Holder With MOD 30ML
MOD 30ML Application
LOADING THE COMPOUND
The following procedure assumes that the Application Builder is open, you are in a Loop
Block and the output holder compound is located in the compounds directory of the
Application Builder.
To load the output holder compound (PID_OPH.CSM):
1. Select the Compounds icon
mouse key (see Figure 1).
2. Select Load
output holder compound has been saved in the compounds directory of the
Application Builder you should select that directory now. Otherwise select the drive or
directory that the output holder compound is located in.
3. Double click on the output holder compound (PID_OPH.CSM) to load it in your
strategy.
4. Answer NO
should now have a block on your screen that is labeled “CPD”.
5. Select the CPD block once to high-light the block. Select the Query icon
then select the block again. Enter a loop name in the “Block Tag” field. Click “enter”
to save it.
6. Double click on the block to open it. Figure 3 shows what the output holder with PID
loop strategy looks like.
7. Double click on the DISP block and enter your tag in the “Display Tag” field and then
select “enter” from the DISP block to save it. This same tag name must be entered in
the DIF block.
to the question “Do you wish to retain block occurrence numbers”. You
from the Compounds menu. A directory menu will appear. If the
located at the top of the screen using the right
and
8. Click the blue diamond
up two levels.
9. Double click on the DIF block to open it.
10. Click once on the “Edit Display List” arrow. The program will open to a text editor.
Type in the tag name that you placed in the DISP block display tag field (Step 7). It
must be in quotation marks and be typed exactly like it appears in the DISP block. An
example is as follows; “TIC-100”;. Be sure to include the semi-colon at the end of the
tag name. Select “Exit” from the “File“ menu and save the text file. Exit the DIF block
by selecting “Enter”.
11. Make the “RUNINIT” connection between the IF block and the output holder
compound block before returning to the loop compound. To do this select the
connection tool
connection block. Complete the connection by selecting the oval loop compound. A
8
in the upper left hand corner of the screen twice to move
at the top of the screen and select “RUNINIT” from the IF
Using The Output Holder With MOD 30ML
MOD 30ML Application
menu will appear with the tag name you gave the output holder compound. Select
that tag and hit “OK”. A new menu will appear with the attribute “RUNINIT” in it.
Select “RUNINIT”. The connection is now complete. Release the connection tool by
clicking the right mouse key.
12. Double click on the oval loop block to return to the compound block. Enter all of the
necessary engineering values in the Input Conditioning and PID blocks.
NOTE: Caution must be exercised if reassigning I/O in the output holder strategy. The
execution order for the blocks of this strategy are specific for the configuration to
work properly. Table 2 shows an example of block execution order.
Table 2. Block Execution Order
Tag Name Type Exec Occur
PV AIN 0 1
pv_i VCI 1 1
RETURN AIN 2 2
SENSE DIM 3 1
RETURNF1 VCI 4 2
SENSF DI 5 1
#001 CIB 6 0
OP_T_LGC EX 7 1
pid PID 8 1
op_ao AOUT 9 1
disp DISP 10 1
TL_ctrl LT 11 1
Notes DESC 12 0
Note that the process variable input, Return input, Sense input, and OP_T_LGC
expression block must run prior to the PID block. The Return and Sense inputs must run
prior to the OP_T_LGC expression block. The PID block must run prior to the analog
output. If using the PID and Output Holder compound and making new I/O assignments,
be sure the block execution order is as shown in Table 2.
Block execution order can be altered using the Execution/Occurrence tool
the top menu, left side.
1. Click once on the
execution order and occurrence numbers.
2. Change the block execution order by selecting the execution order field next to the
block you wish to change and entering the appropriate execution values. Remember
that no two blocks can have the same execution order number. If you change one
block to read an execution order number that is currently assigned to that of another
block you must also change the original block with that number.
tool and select “manual”. A table will appear that shows the
located on
9
Using The Output Holder With MOD 30ML
MOD 30ML Application
OUTPUT HOLDER COMPOUND THEORY OF OPERATION
When the instrument powers up the process value is read first followed by the Return and
Sense inputs. The expression block “OP_T_LGC” is executed next with a result that
becomes true when both the sense and run initialization inputs are true. The sense input
will always be true when an output holder card is present. The run initialization input is
true for only a moment when the instrument first powers up. The output of the expression
block is connected to the track command input of the PID block. For this brief moment
that the expression block output is true the PID block output will track the Return input
connected to its track source. The PID block uses this output value until told to change
based on automatic or manual manipulation. This PID output value is sent to the output
block causing the output blocks output current to be equal to that of the Output Holder
output.
The Return input block is set up to receive 1 to 5 milliamps. Its input conditioning block
converts this to 0 to 100 as engineering units that correspond to the PID block output.
The initial value of the Sense input block and its corresponding input conditioning block
are set to false. As well the output blocks initial value is also set to zero. This permits the
output holder card to maintain control of the field device until the controllers output is
synchronized to the output holders output.
The TL_ctrl” tune list permits front face changes of the P,I&D values.
10
The Company’s policy is one of continuous product improvement and the right
is reserved to modify the information contained herein without notice, or to
make engineering refinements that may not be reflected in this bulletin.
Micromod Automation assumes no responsibility for errors that may appear in
this manual.
© 2004 MicroMod Automation, Inc. Printed in USA
IB-MLAPP-OH, Issue 2 04/2005
MicroMod Automation, Inc.
75 Town Centre Drive
Rochester, NY USA 14623
Tel. 585-321 9200
Fax 585-321 9291
www.micromodautomation.com
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