COMPTROL DH151 Series User manual

SERIES DH151/DK151
SINGLE RANGE MONOCELLS
INSTRUCTION MANUAL D-131
1
Copyright 2023 - Revised, Comptrol All Rights Reserved
PART I - DESCRIPTION
I-A GENERAL INFORMATION
Comptrol Loadcells are force transducers especially
designed to measure and control web tension on
continuous strip processing lines. Loadcells are normally
installed in matched pairs under the pillow block bearing
at each end of a measuring roll. (See Figure 1)
A loadcell consists of a unique combination of two
integral systems (one mechanical, the other electrical)
for converting the mechanical force of strip tension into
an electrical signal which is directly proportional to the
strip tension.
The Series 151 Monocell was developed for paper
industry applications where the roll's tare weight is
usually in excess of the force created by the strip
tension. These units are applied only in a horizontal
base mounting configuration.
The pendulum affect created by the tare weight is
minimized by placing the patented Comptrol "C" Flexure
adjacent to the Monocell centerline of operation.
The Model DH151 is designed for application where the
resultant strip tension force components cause the
Monocell Load Table to deflect toward the Base Plate.
The deflection of the Load Table toward the Base Plate
caused by the tare and strip tension forces is defined as
the "Compression Mode". The small tare force
component can be zeroed out by following the Electrical
Zero Adjustment procedure outlined later in this bulletin.
When the Monocell is required to operate in the
Compression Mode, the centerline of the roll bearing is
to the left of the center of the flexure, as illustrated on
Page 4.
The Model DK151 is designed for applications where
the resultant strip tension forces cause the Load Plate
to deflect away from the Base Plate. The deflection of
the Load Table away from the Base Plate is defined as
the "Tension Mode". In these cases, the centerline of
the roll is to the right of the pivot point of the Comptrol
"C" Flexure. The small force created by the tare weight
of the roll is then in the tension mode.
The choice of tension or compression modes of
operation ensure that the forces created by the
resultant of the roll weight and strip tension are always
in the same direction. The Comptrol patented "C"
Flexure is ground to different thickness for each inch-
pound rating.
Except for the difference in ratings and mode of
operation (compression or tension), the DH151 and
DK151 are exactly alike, including the Bearing Mounting
Plate, which is reversible to create the change of
centerline of the Monocell "C" Flexure.
Roll unbalance, vibration and other factors which can
distort the Monocell output signal are minimized
because of the low tare force components.
Table of Contents
General Information………………………....1
Installation andOperation-……………........…3
Dimension Drawings.…………….…....4-6
Adjustments......…………………......……7
Troubleshooting.....................................10
Recalibration..........................................11
How to Order............. ..................................12
Application Review.................................13

SERIES DH151/DK151
SINGLE RANGE MONOCELLS
INSTRUCTION MANUAL D-131
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Copyright 2023 - Revised, Comptrol All Rights Reserved
Applications which create a resultant force within nine
degrees of vertical (171 to 189° or 351 to 9°), should be
discussed with Comptrol's application engineers.
I-B THE MECHANICAL SYSTEM
The mechanical system consists of a patented "C-
Flexure Pivot Assembly" which includes a Load Table, a
frictionless elastic pivot or "hinge" and a rugged Base
Plate. (See Figure 2). This assembly allows the
deflection of the Load Table to move toward or away
from the Base Plate. Deflection toward the Base Plate is
defined as the "Compression Mode", while deflection
opposite is defined as the "Tension Mode". An integral
adjustable Mechanical Stop is provided to limit the
amount of deflection in either mode.
An adjustable Viscous Damper is incorporated in the
mechanical system to allow control of the loadcell's
response to rapid changes in apparent signal
fluctuations resulting from such conditions as slight roll
imbalance, variations in the strip material, or the
operation of the machine. The damper is designed to
provide a wide range of stepless, infinitely small
adjustments.
I-C THE ELECTRICAL SYSTEM
The electrical system consists of a Linear Variable
Differential Transformer (LVDT) which converts the
mechanical deflection of the load table into a useful
electrical output signal. (Figure 3) The movable core of
the LVDT is mechanically coupled to the load table by
means of a core wire and crossbar assembly, and a
spring loaded zero adjusting assembly.
I-D TYPE “C” DC LVDT
As illustrated in Figure 4, a DC LVDT consists of the
following components:
• A temperature compensated oscillator network,
which converts the DC input voltage into a high
frequency alternating current for exciting the
Primary Coil (P1).
•A Primary Coil (P1)
•A movable, permeable metallic core.
•Two Secondary Coils (S1and S2).
•A demodulator and summing network to rectify and
integrate the currents from the secondary coils.
Depending on the position of the movable core within
the body of the LVDT, the integrated DC output signal
will be positive (+) or negative (-) with respect to
common. (i.e., The Blue lead will be negative with
respect to the Green with the loadcell in the
Compression Mode, and positive with respect to the
Green with the loadcell in the Tension Mode.)
Regardless of the polarity of the output signal, it will be
directly proportional to the amount of deflection of the
load table. When the core is positioned at the
electrical center of the LVDT (i.e., with no deflection)
the output signal will be zero.
With Comptrol LVDT's the input and output
circuits are electrically isolated from each other
and from the mechanical structure of the loadcell. Thus,
they may be used in "floating ground" or "ground return"
systems.
In operation, the output signal from both loadcells (one
at each end of the measuring roll) are summed to
provide a single output. This output maybe used to drive

SERIES DH151/DK151
SINGLE RANGE MONOCELLS
INSTRUCTION MANUAL D-131
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Copyright 2023 - Revised, Comptrol All Rights Reserved
a digital or analog indication meter, or as a "feedback"
signal for "close loop" tension controls
PART II - INSTALLATION AND OPERATION
II-A INSPECTION UPON DELIVERY
Comptrol Monocells are carefully packaged in sturdy
reinforced cartons or wooden boxes and are securely
blocked or bolted in place.
1. Upon receipt, examine the exterior of the container for
obvious damage or tampering.
2. Check the contents against the packing list.
3. Promptly report any damage or shortage to both the
carrier and Comptrol.
II-B HANDLING
Most Series DH150 Monocells can be handled manually.
II-C LONG TERM STORAGE
While Comptrol loadcells are plated, exposure to
weather, dirt, or moisture should be avoided when they
are stored.
II-D MECHANICAL INSTALLATION
NOTE: The following procedures assume that two
loadcells, one at each end of the measuring roll are
being installed. Refer to the Dimension Drawings on
Pages 4 and 5 of this manual for detailed identification of
all parts.
1. Check that the mounting surfaces to which the
loadcells are to be mounted are flat to within 0.002-
inch T.I.R.
2. Refer to the loadcell Dimension Drawings on Pages4
and 5 for the size, location and orientation of the
Base Plate mounting holes to be drilled and tapped in
the stands or base structures. (NOTE: When the
loadcells are mounted, the conduit box cover or
electrical connector must be accessible)
3. Drill and tap the holes in the stand or base mounting
structure to accept the loadcell mounting bolts. (See
Dimension Drawings on Pages 4 and 5)
4. Assemble the loadcells to the stands or base
mounting structures.
5. Assemble the adapter plates to the loadcells.
6. Assemble the pillow block bearings onto the
measuring roll.
7. Assemble the measuring roll and pillow block
bearings onto the loadcell adapter plates.

SERIES DH151/DK151
SINGLE RANGE MONOCELLS
INSTRUCTION MANUAL D-131
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Copyright 2023 - Revised, Comptrol All Rights Reserved

SERIES DH151/DK151
SINGLE RANGE MONOCELLS
INSTRUCTION MANUAL D-131
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Copyright 2023 - Revised, Comptrol All Rights Reserved

SERIES DH151/DK151
SINGLE RANGE MONOCELLS
INSTRUCTION MANUAL D-131
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Copyright 2023 - Revised, Comptrol All Rights Reserved

SERIES DH151/DK151
SINGLE RANGE MONOCELLS
INSTRUCTION MANUAL D-131
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Copyright 2023 - Revised, Comptrol All Rights Reserved
II-E MECHANICAL ALIGNMENT
1. Align measuring roll and pillow block bearings to
avoid any mechanical binding or friction. The
measuring roll must be level and perpendicular to
the path of the strip material for accurate tension
measurement.
2. Using an open-end wrench and a dial indicator or
feeler gauge, adjust the Mechanical Stop for the
required clearance between the Load Table and the
Mechanical assembly. (Refer to Figure 5 & 6 on
Page 3) This is accomplished by having the Tare
applied and the Load Table not in contact with the
Mechanical Stop.
3. Thread the strip material on the measuring roll
andchecktomake surethe wrapangle is the same
as the wrap angle specified on the calibration
sheet. If the wrap angle is not the same, contact
Comptrol.
II-F ELECTRICAL INSTALLATION
(Read the entire electrical wiring procedure before
proceeding.)
1. Turn off all electrical power to the loadcell.
2. Remove the conduit box cover and hole plugs to gain
access to the LVDT terminal boards.
3. Use twisted four conductor signal cable, Belden 9402,
or equivalent in grounded steel conduit, from the LVDT
to the control panel.
4. Observing correct polarity, connect the input power
leads to bottom Terminal 1 and 2 on the Terminal
Board. (For correct polarity refer to Figure 7)
5. Connect the output signal leads to the bottom
Terminals 3 and 4 on the Terminal Board.
6. Make certain all wires and leads are dressed away
from the core wire and crossbar assembly. The LVDT
may be inoperative if movement of the crossbar is
restricted in any way.
7. Repeat Steps 1 through 6 of the electrical wiring
procedure for the loadcell mounted on the opposite
end of the measuring roll.
II-G ELECTRICAL ZERO ADJUSTMENT
(Read the complete Electrical Zero Adjustment
procedure before proceeding with the adjustment.)
1. Disengage strip from the measuring roll so that no
tension force is applied to the loadcell.
2. Connect a voltmeter to Terminals 3 and 4. (See
Figure 7)
3. Apply 24-volt DC electrical power to the loadcell
observing the correct polarity. [Plus (+) to Terminal 1
and minus (-) to Terminal 2]. Do not exceed the
maximum rated input voltage.
NOTE: Allow 20 minutes for the loadcell to warmup
before taking first readings to insure accurate readings.
4. Measure the output voltage of the LVDT between the
Green and Blue leads with a voltmeter with a sensitivity
of at least 100,000 ohms per volt. The output voltage
should be between zero.

SERIES DH151/DK151
SINGLE RANGE MONOCELLS
INSTRUCTION MANUAL D-131
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Copyright 2023 - Revised, Comptrol All Rights Reserved
5. If the output is not zero, remove the dust cap located
on the load table to gain access to the zero
adjustment screw. (See Figure 8)
6. Using a 7/64-inch hex key, turn the zero-
adjustment screw several turns counter clockwise
(CCW). Then, slowly turn the adjusting screw
clockwise (CW) until a zero reading is obtained on
the voltmeter. If the zero position is passed, turn
the adjusting screw counter clockwise (CCW) pass
the zero point. Then turn the adjusting screw back
in a clockwise (CW) direction until the meter reads
zero volt.
7. Deflect the Load Table of the loadcell by applying
pressure in the direction the tension force will be
applied. This may be done manually or with a
lever. A change in the output voltage signal should
be noticed.
NOTE: The polarity of the output signal will be
positive (+) for deflection in the Compression
Mode, and negative (-) for deflection in the Tension
Mode.
8. Release the force applied to the Load Table should
allow the output signal to return to zero.
If the output signal does not return to zero, make
sure the measuring roll rotates freely. Check for
improper alignment of the measuring roll and for
friction or binding with the pillow block bearing.
Also check that the LVDT crossbar assembly is
free of any interference. Repeat Steps 1 through 8.
If the output signal still does not return to zero,
contact Comptrol.
9. Repeat Steps 1 through 8 for the loadcell mounted
on the opposite end of the measuring roll.
II-H FULL LOAD ADJUSTMENT
After the loadcell has been zeroed, a pull test can be
made to check the output voltage of the loadcell at full
load. (See calibration sheet for voltage output)
1. Run a non-stretchable rope over the center of the
tension roll simulating the web path. (NOTE: the rolls
should be free to turn)
2. With one end of the rope secured, hang a known
weight, equally over the roll so that the total tension is
equal to the maximum strip tension specified on the
calibration sheet, at the other end. (See Figure 9A)
For larger tension where dead weights would be too
large, a crane scale can be used to simulate maximum
strip tension. (See Figure 9B)
3. With a voltmeter connected to the bottom Terminals 3
and 4 of the Terminal Board, maximum output voltage
will be observed.
4. Repeat Step3 for the loadcell mounted on the opposite
end of the measuring roll.
5. Recheck to make certain that all leads are dressed
away from the LVDT crossbar assembly on both
loadcells and replace both conduit box covers.
Comptrol loadcells instrumentation provides the required
signal conditioning and a reliable high level output signal
for use as feedback control of a tension drive system.
The feedback signal is directly proportional to the strip
tension applied. If a Comptrol control is used, refer to the
control manual for further calibration.
Although the electrical output of Comptrol Monocells are
sufficient to drive most electrical indicators, substantial
signal conditioning is normally required for effective
tension instrumentation system control. Refer to the
documentation available from the instrumentation
supplier for more information.

SERIES DH151/DK151
SINGLE RANGE MONOCELLS
INSTRUCTION MANUAL D-131
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Copyright 2023 - Revised, Comptrol All Rights Reserved

SERIES DH151/DK151
SINGLE RANGE MONOCELLS
INSTRUCTION MANUAL D-131
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Copyright 2023 - Revised, Comptrol All Rights Reserved
II-J VISCOUS DAMPER ADJUSTMENT
The Viscous Damper allows for adjustment of the
loadcell output signal for signal fluctuations resulting
from such conditions as slight roll imbalance,
variations in the strip material, or the operation of the
machine.
The calibrated dial is graduated from "0" to "10". The
damping effect is minimum at "0" and maximum at"10".
Adjustment between these two points is stepless.
Because the need for damping becomes apparent
only
under dynamic conditions, damper adjustment must
be made while the strip is moving through the process
at normal speed.
NOTE: For best performance the Viscous Damper
should be set as close to zero as possible without the
mechanical stop contacting the load plate.
To Adjust the Viscous Damper:
1. Connect a chart recorder to the Terminal 3 and 4 on
the bottom of the Terminal Board.
2. Record the loadcell output signal
while the line is running. The chart
will show the frequency and
amplitude oftheoscillation of theTop
Plate.
3. Using a 3/16-inch hex key, rotate the adjustment
dial clockwise or counterclockwise along the
calibrated scale until the variation of the fluctuation of
the output signal is minimal.
NOTE: Rotating the dial beyond the "0" or "10"
markings on the scale has no effect on the damper
adjustment.
PART Ill - TROUBLE SHOOTING
When properly installed in accordance with the original
design specifications, Comptrol Monocells should
require little or no regular maintenance or service.
Certain conditions, however, can impair their inherently
accurate and reliable performance. Therefore, if trouble
should arise, the following conditions should be checked.
III-A MECHANICAL
1. Has the tension measuring system been changed?
a. An increase or decrease in strip tension (Refer to A
on the calibration sheet for specified web tension)
b. An increase or decrease in the wrap angle. (Refer
to B on the calibration sheet for the specified wrap
angle)
If any of the above parameters have been
changed, recalibration may be required. (Refer to
Recalibration Procedure, Page 11)
2. Aretheloadcells mounted securely?
a. Base Plate to Mounting Stand?
b. Adapter Plate to Load Table?
c. Pillow Block bearing to Adapter Plate?
3. Istensionmeasuringrollinproper alignment and
does it turn freely?
4. Are Pillow Block bearingsand sealsfreeof all
bindingand stickiness? Are they worn?
5. Are the Metering Clamps on the loadcell
securely tightened?
6. Are the Mechanical Limit Stops correctly
adjusted? (Refer to Mechanical Alignment on
Page 7)
7. Are the Viscous Dampers correctly adjusted?
(Refer to Viscous Damper Adjustment, Page 10)
III-B ELECTRICAL
1. Are LVDT's receiving correct input volage?
Check line voltage, fuses or circuit breakers,
and power switches.Check power supply output
and voltage to LVDT's.
2. Are all connections secure?
Check for continuity. Retighten all connections.
Recheck operation.
3. Are LVDT's mechanically secure in their
mounting and clamps?
If loose, recenter, tighten, and readjust electrical
zero.