COMPTROL DST226C User manual

MODEL DST226C
SINGLE RANGE SUPERLOADCELLS
INSTRUCTION MANUAL F-102
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.
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.
The mechanical system also includes an adjustable
Cantilever Spring Assembly mounted between the Load
Table and the Base Plate in such a manner as to oppose
deflection in either mode. A Metering Clamp allows the
adjustment of the effective length of the Cantilever
Springs.
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. (See 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.
Table of Contents
General Information………………………....1
Installation andOperation.……………........…2
Adjustments…………………………........5
Troubleshooting…………………......……6
Recalibration.......................................... 8
Application Review................................11

MODEL DST226C
SINGLE RANGE SUPERLOADCELLS
INSTRUCTION MANUAL F-102
2
Copyright 2023 - Revised, Comptrol All Rights Reserved
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
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 loadcells 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 Incorporated.
II-B HANDLING
Most loadcells can be handled manually. Those that
cannot (Models 600, 601, 602) should be lifted by a hoist
or other means using ropes placed around the Base
Plate.
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 Drawing on Page
3 of this manual for detailed identification of all parts.
1. Remove the adapter plates from the loadcells.
2. Drill and tap the adapter plates to accept the selected
pillow block bearings.
NOTE: THE CENTERLINE OF THE PILLOW BLOCK
BEARING MUST COINCIDE WITH THE CENTERLINE
OF LOADING (℄) OF THE LOADCELL. Refer to the
appropriate Dimension Drawing on Pages 3.
3. Check that the mounting surfaces to which the
loadcells are to be mounted are flat to within 0.002-inch
T.I.R.
4. Refer to the loadcell Dimension Drawing on Page 3 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.)

MODEL DST226C
SINGLE RANGE SUPERLOADCELLS
INSTRUCTION MANUAL F-102
3
Copyright 2023 - Revised, Comptrol All Rights Reserved
5. Drill and tap the holes in the stand or base
mounting structure to accept the loadcell mounting
bolts. (See the appropriate Dimension Drawing on
page 3)
6. Assemble the loadcells to the stands or base
mounting structure.
7. Assemble the adapter plates to the loadcell.
8. Assemble the pillow block bearings onto the
measuring roll.
9. Assemble the measuring roll and pillow block
bearings onto the loadcell adapter plates.

MODEL DST226C
SINGLE RANGE SUPERLOADCELLS
INSTRUCTION MANUAL F-102
4
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). 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 rolland
check to make sure the wrap angle 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.

MODEL DST226C
SINGLE RANGE SUPERLOADCELLS
INSTRUCTION MANUAL F-102
5
Copyright 2023 - Revised, Comptrol All Rights Reserved
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 Terminal 3 and 4 at the top of
the Terminal Board. (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.
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 adjusting
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.

MODEL DST226C
SINGLE RANGE SUPERLOADCELLS
INSTRUCTION MANUAL F-102
6
Copyright 2023 - Revised, Comptrol All Rights Reserved
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 Step3for 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 loadcells 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.
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 bestperformancetheViscousDamper 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 ofthe
topplate.
3. Using a 3/16-inch hex key, rotate
the adjustment dial clockwiseor counterclockwise
alongthecalibrated scale,until thevariation of the
fluctuation of the output signals 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 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 web 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 8)

MODEL DST226C
SINGLE RANGE SUPERLOADCELLS
INSTRUCTION MANUAL F-102
7
Copyright 2023 - Revised, Comptrol All Rights Reserved

MODEL DST226C
SINGLE RANGE SUPERLOADCELLS
INSTRUCTION MANUAL F-102
8
Copyright 2023 - Revised, Comptrol All Rights Reserved
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 bearings and seals free of all binding
and 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 4)
7. Are the Viscous Dampers correctly adjusted?
(Refer to Viscous Damper Adjustment, Page 6)
III-B ELECTRICAL
1. Are LVDT's receiving correct input voltage?
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.
4. Are electrical zero adjustments, correct?
Readjust electrical zero. (See Electrical Zero
Adjustment on Page 5)
5. Are LVDT's open or shorted?
To check, turn off power and disconnect the input
and output leads. Check coil continuity and
resistance.
a. Red (Terminal 1) to Black (Terminal 2)
should be in excess of 2 megohms.
b. Red (Terminal 1) or Black (Terminal 2) of LVDT
should be in excess of 5 megohms.
c. Green (Terminal 3) to Blue (Terminal 4) should
be approximately 20,000 ohms.
d. Green (Terminal 3) or Blue (Terminal 4) to
LVDT should be in excess of 5 megohms.
If LVDT circuits are open or shorted, replace LVDT.
Replacement units are available from the factory.
Contact Comptrol with loadcell model number and serial
number.
PART IV- RECALIBRATION PROCEDURE
All Comptrol loadcells are factory calibrated before
shipment, as specified in the purchase order. However, if
any of the following parameters vary from the original
design specifications, recalibration will become
necessary.
1. Strip Tension (Refer to A on calibration sheet for
specified strip tension)
2. Wrap Angle (Refer to B on calibration sheet for
specified wrap angle)
3. Inclination of the Passline (Refer to C on calibration
sheet for specified Passline)
4. Mounting Angle (Refer to N on the calibration sheet
for specified mounting angle)
Should recalibration become necessary, it is strongly
recommended that the loadcell be returned to the factory
with complete specifications.
When this is impractical or impossible, recalibration can
be performed after installation in strict accordance with
the following procedure.

MODEL DST226C
SINGLE RANGE SUPERLOADCELLS
INSTRUCTION MANUAL F-102
9
Copyright 2023 - Revised, Comptrol All Rights Reserved
IV-A RECALIBRATION AFTER INSTALLATION
Loadcell recalibration involves changing the spring
length which in effect changes the calibrated operating
load capacity of the unit. This is accomplished by
increasing or decreasing the spacing between the
opposing faces of the front spring clamp and the
metering blocks. (Refer to Figure 11)
Increasing the spring length decreases the operating
load capacity of the unit. Decreasing the spring length
increases the operating load capacity.
NOTE: The operating load capacity must not exceed the
maximum load rating of the unit.
Before making any adjustments, calculate the new
spring length required to obtain the desired operating
load capacity using the following formula:
Where: J = old capacity
Jnew = desired new capacity
L = measured spring length
Lnew = new spring length
Note: The spring length should not be less than 3
inches.
Comptrol recommends removing the units from the
equipment to gain access to the unit and components
during recalibration.
If the units must be recalibrated while installed on the
equipment:
1. Turn off electrical power to the loadcell.
2. Remove the strip material from the measuring roll to
eliminate any tension load upon the loadcell.
3. Check that the load plate is parallel to the base plate
(+ .020"). This in effect removes the tare weight acting
on the load plate. Depending on the load capacity of
the units and the applied tare weight, the load table
may require the use of a prying or clamping device to
force the load table parallel to the base plate, and
blocking it to maintain the position. (Refer to Figure
11 before proceeding with Step 3a or 3b)
a. For units with the tare weight acting in
compression on the load plate, adjust the bottom
mechanical stop head toward the load plate until
the load plate and base plate are parallel.
b. For units with the tare weight acting in tension on
the load plate, loosen the bottom mechanical stop
head away from the load plate until the load plate
and base plate are parallel.
If the unit is recalibrated off the machine, remove the
pillow block bearing and secure the unit to a bench or
fixture to prevent the unit from moving.

MODEL DST226C
SINGLE RANGE SUPERLOADCELLS
INSTRUCTION MANUAL F-102
10
Copyright 2023 - Revised, Comptrol All Rights Reserved
To Adjust the Spring Length:
1. Measure the spring length.
2. Loosen the two-metering clamp outer hex head bolts
(closest to the outer edge of the unit.)
3. Loosen the two inner metering clamp hex head bolts.
4. Clean the spring assembly and metering clamp to
remove any debris or contaminates to insure proper
clamping.
5. Adjust the metering clamp along the spring assembly
to attain the new calculated spring length "Lnew".
6. With the metering clamp square to the spring, tighten
all the bolts until each bolt head contacts the metering
clamp and the metering clamp contacts all three
prongs of the spring assembly.
7. Tighten the two inner bolts on the metering clamp
extremely tight.
8. Tighten the two outer bolts on the metering clamp
extremely tight.
9. Remove any blocking and/or clamping devices, and
adjust the mechanical stop as specified in
Mechanical Alignment, (Section II-E, on Page 4).
10. a. If the units are recalibrated off the machine,
refer to the procedures in Section II-A
through II-J to re-install.
b. If the units are recalibrated on the machine,
re-adjust the electrical zero as specified in
Section II-G, Electrical Zero Adjustment.