Meridian Manual 8/02 ENG - Field Environmental Instruments, Inc.

Meridian Manual 8/02 ENG - Field Environmental Instruments, Inc.
L6-20 Level (Model 44-8824)
L6-20 / LT6-900 Owner's Guide
L6-20 Level and
LT6-900 Level-Transit
Made in U.S.A.
LT6-900 Level-Transit (Model 44-8834)
For customer service, call (781) 848-7702
With David White
your sights are set
on precision and accuracy.
Congratulations! You’ve purchased a David White builder/contractor
instrument, American-made and known throughout the world for
precision and accuracy.
The purpose of this booklet is to acquaint you with the instrument,
its components, proper care and handling.
Our levels and level-transits are constructed to withstand
extremely rugged field use. Like all precision instruments,
however, they should be treated with reasonable care to
prolong life and accuracy.
Quality and innovation since 1900.
All instruments are adjusted when they are shipped from the
factory. It is the customer’s responsibility to check and to ensure
instruments are adjusted prior to using.
David White is not responsible for errors caused by instruments
that are out of adjustment.
Contact your distributor, dealer or David White for
information on the nearest facility to check if your instrument
is properly adjusted. Some customers may choose to check
the instrument themselves. This can be done by following
the “Checking for Calibration” instructions at the back of this
manual. All actual adjustments must be done by a qualified
service facility.
All specifications are subject to change without notice.
Meridian L6-20 Level
Meridian LT6-900 Level-Transit
Optimum sighting range: Recommended job range up to 200 feet.
Accuracy range: Recommended for jobs requiring accuracy within
1/4" at 75 feet.
Minimum Focus
Field of View
No. of Lenses
10.5" (26.5cm)
4 ft. (1.2m)
.75" (19mm)
2' @ 100' (.6m @ 30m)
Graduation Diameter
3.62" (92mm)
Each 1°
Each 10°, 0-90-0°
Double direct to 15 min.
VERTICAL ARC (LT6-900 only)
Each 1°
Each 10°, 45-0-45°
Planar bearing
10 min. per 2mm
Instrument only
Instrument, case,
3 oz. plumb bob
3.25 lbs. (1.5kg) 4.5 lbs. (2.0kg)
Double-walled polyethylene
5/8 x 11 JIS
6 lbs. 6 oz. (3kg) 7 lbs. 10 oz. (4kg)
General Description
Meridian L6-20 Level
Meridian LT6-900 Level-Transit
1. Telescope objective lens
2. Eyepiece
3. Focusing knobs
4. Instrument level vial
5. Horizontal graduated circle
6. Horizontal vernier
7. Horizontal clamp
8. Horizontal tangent
9. Telescope lock lever
10. Vertical arc
11. Vertical arc pointer
12. Vertical clamp
13. Vertical tangent
14. Four leveling screws
15. 5/8 x 11 JIS threaded base
The telescope provides a sharp image magnified 20 times. This means the
object sighted appears 20 times closer than it would with the naked eye.
The telescope features a built-in sunshade which protects the objective
lens (1) and reduces glare.
To focus on an object, sight through the eyepiece (2) and turn the focusing knobs (3) with either right or left hand. Cross hairs are in constant
focus. All focusing is internal. The telescope does not move outward or
inward as objects are focused. David White Meridian instruments use the
smooth precision of a rack and pinion mechanism for focusing. Focus
range is from four feet to infinity. For closer focus, turn the knob clockwise.
For farther focusing, turn counterclockwise.
The instrument leveling vial (4) is protected by a strong, die-cast casing,
and is graduated to facilitate centering the bubble.
The horizontal circle (5) can be rotated for easy angle setting and reading and is divided in quadrants (0-90°). The circle is marked by degrees
and numbered every 10 degrees.
The horizontal vernier (6) permits dividing whole degrees into fractions of
1/4° (15 minutes). See page 9 for circle and vernier reading instructions.
Approximate horizontal sightings are held firmly in place by means of a
clamp (7). Then, precise horizontal settings can be made with the tangent
(8). The clamp must be hand tightened in order for the tangent to function.
The Meridian Level-Transit is a combination instrument. Its telescope moves up and down 45 degrees, and rotates 360 degrees, to
measure vertical and horizontal angles.
The telescope lock lever (9) must be in a closed position when
the instrument is to be used as a level; open when used as a
transit for vertical sightings. It is shown in the open position.
The vertical arc (10) is divided in degrees and numbered every 10
degrees up to 45 degrees, for both upward and downward angles,
and has an adjustable index pointer (11).
The vertical clamp (12) holds the telescope at a vertical angle.
Fine vertical settings can be made with the vertical tangent (13).
The vertical clamp must be hand tightened before the tangent will
Both the L6-20 and LT6-900 have four leveling screws (14) for leveling
the instrument. The instrument is mounted to the tripod by screwing the
tripod stud into the 5/8 x 11 JIS threaded base (15).
Setting up your instrument
Each of the following steps is
important in preparing to use your
1. These instruments must be
used with a 5/8 x 11 JIS thread
tripod. For easiest setup and best
operating results, it is recommended that the David White tripod is
used. It is important that the tripod
is set up firmly. Make sure that the
tripod points are well into the
lever to
When setting up on a smooth floor
or paved surface, secure the points
of the legs by chipping the concrete, attaching chains between the
legs, or putting a brick in front of
each leg. If setting up in dirt, apply
your full weight to each leg to prevent settlement.
3 feet
Check the tripod legs. They should
have about a 3 foot spread, positioned so the top of the tripod
head appears level.
If using a tripod with
adjustable legs, be
sure the leg levers are
securely tightened.
1. Loosen clamp
2.Close lock
3. Turn up
1A. Loosen
4. Hand tighten
tripod mounting
2. Before setting up your instrument, loosen the clamps. If using
the level-transit, be sure the telescope lock lever is in the closed
position. Attach the instrument to the tripod securely, hand tightening the tripod mounting stud to the instrument base. If setting
up over an exact point, read step 3; otherwise, continue to step 4.
3. If setting up over a point, use a plumb bob to center on the
exact point. To hang the plumb bob, attach cord to the plumb bob
hook on the screwdriver-style handle of the tripod. Knot the cord
as illustrated.
Move the tripod and instrument over the approximate point. (Be
sure the tripod is set up firmly again, as described in step 1.) Shift
the instrument on the tripod head until the plumb bob is directly
over the point. Then set the instrument leveling screws as
described in step 4.
1. Move tripod and
instrument over the
approximate point.
2. Shift the instrument
to line up plumb bob
4. Turn down the instrument
leveling screws until firm contact is made with the tripod
head. A word of caution: it is
possible to over-tighten the
leveling screws. You want only
a firm contact between the
screws and the tripod head. If
the instrument shifts on the tripod, turn down the screws
more firmly by hand. If no
shifting occurs, the instrument
is ready for Step 5.
Hanging the
plumb bob.
To hang the plumb
bob, attach cord to
the plumb bob
hook on the tripod
and knot the cord
as illustrated.
5. Leveling the instrument so the vial bubble remains centered
through a 360° rotation of the telescope is the most important
operation in preparing to use your instrument. When leveling your
instrument, be sure not to touch the tripod. Follow these instructions carefully.
A. Line up the telescope so
that it is directly over one
pair of leveling screws.
Grasp these two leveling
screws with the thumb and
forefinger of each hand.
Turn both screws at the
same time by moving your
thumbs toward each other
or away from each other,
until the bubble is centered.
B. When the bubble is centered, rotate the telescope 90 degrees over
the second pair of leveling screws and repeat
the thumbs in, thumbs
out leveling procedure
until the bubble is again
C. Shift back to the original
position and check the
level. Make minor adjustments with leveling screws
if necessary.
FOR A FINAL LEVEL CHECK, rotate the telescope over each of
four leveling points to be sure the bubble remains centered.
The Golden Rule for quick and simple leveling is
THUMBS IN, THUMBS OUT. Turn BOTH screws equally
and simultaneously. Practice will help you get the feel of
the screws and the movement of the bubble. It will also
help to remember that the direction your left thumb moves
is the direction the bubble will move.
Reading the circle and vernier
The 360° horizontal circle is divided in quadrants (0-90°). The
circle is marked by degrees and numbered every 10 degrees. To
obtain degree readings, it is only necessary to read the exact
degree at the intersection of the zero index mark on the vernier
and the degree mark on the circle (or on the vertical arc of the
75 degrees
For more precise readings, the vernier scale is used. The vernier
lets you subdivide each whole degree on the circle into fractions,
or minutes. There are 60 minutes in a degree. If the vernier zero
does not coincide exactly with a degree mark on the circle, note
the last degree mark passed and, reading up the vernier scale,
locate a vernier mark that coincides with a circle mark. This will
indicate your reading in degrees and minutes.
75 degrees,
45 minutes
Sighting and focusing
the telescope
Aim the telescope at the object and sight first along the top of the
telescope tube. Then look through the telescope and adjust the
When cross hairs are positioned on or near the target, tighten the
horizontal clamp and make final settings with the tangent to bring
the cross hair exactly on point.
When sighting through the telescope, keep both eyes open. You
will find that this eliminates squinting and will not tire your eyes.
Remember to avoid touching the tripod while sighting.
Removing the instrument from
the tripod
Loosen two adjacent leveling screws and unscrew the tripod
mounting stud while holding onto the instrument. Remove the
instrument from the tripod and secure it in its protective carrying
case. Loosen the vertical clamp and close the lock lever on the
level-transit. Center the telescope in the case.
Care and handling
1. Keep the instrument clean and free of dust and dirt. Clean the
objective and eyepiece lenses using a soft brush or lens tissue.
Rubbing with a cloth may scratch the lens coating and impair the
view. Clean the instrument with a soft, non-abrasive cloth and mild
detergent. Never use solvents or submerge the instrument in
water. Do not attempt disassembly.
2. If the instrument is wet, dry it before you return it to its case.
3. When the instrument is not being used, keep it in its carrying
4. When moving the instrument over a long distance, by foot or by
vehicle, remove it from the tripod and place it in its protective
5. When moving a tripod-mounted instrument, handle with care.
Carry only in an upright position. Do not carry over your shoulder
or in a horizontal position. Improper handling may result in instrument damage.
6. Handle the instrument by its base when removing from the case
or attaching to a tripod.
7. Never use force on any parts of the instrument. All moving parts
will turn freely and easily by hand.
8. All precision instruments should be cleaned, lubricated, checked
and adjusted ONLY at a qualified instrument repair station or by
the manufacturer, at least once a year.
Using your instrument
Levels and level-transits, as do all sighting instruments, operate on
the principle that any point along a level line of sight is exactly
level with any point along that line.
Levels and level-transits
The following jobs can be accurately performed with a level or
level-transit used in the level position (with closed lock lever):
grading for swimming pools, driveways, sidewalks, lawns, gardens; plotting contour plowing lines; laying out drainage ditches;
setting fence lines; estimating cut and fill requirements; setting
forms and footings; leveling walls and foundations; establishing
drainage for landscaping; aligning trees and shrubs and building
terraces and stone walls.
Determining differences in elevation
One of the main uses of levels is for measuring the differences in
elevation for grading.
With the instrument leveled, we know that since the line of sight is
perfectly straight, any point on that line of sight will be exactly level
with any other point.
The above illustration shows how exactly we can check the difference in height (or elevation) between two points. If the rod reading
at B is 5 feet and the reading at C is 6 feet, we know that point B
is 1 foot higher than point C. Using the same principle, you can
easily check if a row of windows is straight, or a wall is level, or
how much a driveway slopes.
Running straight lines with a level
Set up the instrument over Point A. A plumb bob should be held
over Point B. Sight approximately on the plumb bob cord and turn
the telescope so that the vertical cross hair coincides with it. To
align the intermediate points, direct the person with the leveling
rod to the right or left until the rod coincides with the vertical cross
hair. It is important not to move the instrument during operation.
After all points have been set, check back on point B to be sure
that the instrument did not move.
Determining contour lines
Contour lines, such as used for contour plowing, are lines connecting points of equal level. To determine contour lines, first level
the instrument carefully. A sighting rod should be held at the beginning contour line about 100 feet from the instrument. Sight the rod
and set a target on the rod at the point where the horizontal cross
hair intersects the rod. Then move the rod to approximately the
next place where a contour line stake is to be set and move the
rod up or down the slope until the line of sight through the telescope again intersects the target. This determines a second point
on the contour line. This step is repeated as many times as necessary.
If the person holding the rod is moving too far from the instrument,
simply hold the rod in one of the positions determined from the
original instrument position and move the instrument to another
convenient location along the contour. Sight on the rod in this position and move the target up or down until it lines up with the cross
hair. The line may then be continued in the same manner as
Measuring and laying out angles
For measuring angles, attach a plumb bob cord to the hook on the
screwdriver-style handle of the tripod. The point of the plumb bob
will then indicate a point on the ground directly below the center of
the instrument and, therefore, will also indicate the center of all
angles to be measured. This point should be marked by a stake
about two inches square with a tack indicating its center.
Horizontal angles are always read at the vernier zero mark. (See
"Reading the circle and vernier," page 9.) The following example
simply explains how to measure angles:
Set the instrument up at station 1. Place it so the plumb bob is
directly over station 1. Now level the instrument as explained previously. Turn the telescope so that the vertical cross hair is directly
in the center of the rod at station 2. Set the horizontal circle at
zero to coincide with the vernier zero. Then turn the telescope to
sight on station 4 and read the angle. (In this case, it would be
120 degrees.)
Move the instrument and tripod to station 2 and level exactly as
before. When the instrument has been leveled, sight back to read
on station 1. Set the horizontal circle to zero, then sight the telescope to locate station 3 and read the angle (90 degrees). Move
the instrument and tripod to station 3 and level as before. Again,
sight back to the previous station (2) and set the circle at zero.
Turn the telescope to sight on station 4. Your angle should be 105
degrees. The same procedure is followed to measure the angle at
station 4.
You can prove the accuracy of your reading by adding the four
inside angles together because the total of the inside angles of a
quadrangle is always 360 degrees.
To lay out an angle, proceed in the same way as in measuring an
angle. Set the instrument at station 1, level it, and set the circle at
zero. Swing the telescope to the desired angle and move the rod
to intersect the vertical cross hairs. This establishes your angle.
NOTE: The L6-20 and LT6-900 have horizontal verniers which
read to 15 minutes (1/4 degree). For projects which need more
accurate angle measurement for layout, we recommend using a
more precise instrument with a 5 minute vernier.
Laying out a swimming pool
In the above figure, A-B is the lot line. The corner of the proposed
swimming pool is E. Point C is the point where the line forming the
side of the pool intersects this lot line. If E has not already been
determined, set up and level the instrument directly over point C
and line up the cross hairs on B. Set horizontal circle to zero. Turn
the telescope 90 degrees to the right.
The vertical cross hair of the instrument will now cut across point
E and point G. Measure the distance from the lot line to the corner
of the pool, which is C-E. Also, the distance E-G is measured
along this line. Place a stake at points C, E and G.
Next set up and level the instrument directly over point E and line
up the cross hairs on G. Set reading to zero. Turn the telescope
90 degrees to the left to establish the line E-F. Measure out the
distance and place a stake at point F. The distance, D-F, (from F
to the lot line) will exactly equal E-C if the work is correct.
Next set up and level the instrument over point F and set the vertical cross hair at point E. Set reading to zero. Turn the telescope
90 degrees to the left to establish the line F-H. Measure out the
distance and place a stake at point H.
Using your instrument
The following example illustrates how to use a level-transit for laying
out roads, building lines, ditches, orchards, fences, hedges, fields, etc.
Running straight lines with a level-transit
(Although it is possible to run straight lines with a level, it is faster
and more accurate to use a level-transit.)
To run a straight line between stakes A and E, position the instrument directly over A. After you level the instrument, release the
lock that holds the telescope in the level position and swing the
instrument until point E is aligned with the vertical cross hair.
Tighten the horizontal clamp so the telescope can move only in a
vertical plane. By pointing the telescope up or down, points B, C
and D can be located.
Establishing vertical lines and planes
It is necessary to use a level-transit instrument for taking vertical
sights, such as lining up a building wall, aligning piers or fencing,
flagpoles, T.V. antennas, plumbing windows or doorways, etc.
To establish vertical lines and planes, first level the instrument,
then release the locking levers which hold the telescope in the
level position. Swing the telescope vertically and horizontally until
the line to be established is directly on the vertical cross hair. If the
telescope is rotated up or down, each point cut by the vertical
cross hair should be in a vertical plane with the starting point.
All components not described on pages 3 and 4 including
adjustment screws and nuts, have been factory set and
should not require handling or readjustment. Tampering
with these factory-adjusted components may impair accuracy or damage the instrument. Only trained technicians
should service this instrument.
Instrument service and repair
Your David White instrument is a precision-made optical instrument and like all good precision tools requires reasonable care
and careful handling. It is recommended that all instruments be
serviced by a reliable instrument repair station at least once a year
to insure accuracy and reliable performance.
If the instrument has been dropped or severely jarred, the instrument's line of sight may be affected. The line of sight must be
exactly perpendicular to the vertical axis of the instrument. This is
checked by the two-peg adjustment system. This method is a specialized procedure and should be conducted only under ideal conditions and only by qualified instrument personnel.
For Customer Service, Parts, and Repair
Customer Service E-Mail:
Checking for calibration
Your David White instrument must be serviced and repaired
by an authorized David White service center. You may, however,
choose to check the instrument yourself to make sure it is properly
adjusted. A simple, inexpensive setup can be established to check
an instrument’s line of sight:
1. Locate an area to set up a tripod that is 10 feet away from a
wall, post, permanent shelving, etc. and approximately 75 feet
to 100 feet away (at a 90° angle) from another wall, post, etc.
2. Using an automatic level or other high-accuracy instrument
known to be in perfect adjustment, secure it to the tripod and
level it following instructions in the instrument’s owner’s manual.
3. Make sure the tripod is on a firm base and mark the location
of the tripod shoe points. These marks can be used for future
4. After the instrument has been completely leveled, sight on the
wall that is 10 feet away.
5. Place a two-foot section of rod ribbon on the wall so the
horizontal cross hair of the instrument intersects the middle of
the two-foot section.
6. Rotate the instrument 90° and sight on the wall that is about
75 feet to 100 feet away.
7. Place a two-foot section of rod ribbon on that far wall so the
horizontal cross hair of the instrument intersects the middle
of the two-foot section (as in Step 5). Adjust this rod ribbon so
that it reads the same exact point as the closer ribbon. Secure
ribbon with tape or glue.
8. Now put the instrument to be checked on the tripod and take
a reading on the ribbon 10 feet away. Record the reading.
9. Rotate the instrument 90° and take a reading on the distant
10. Compare the two readings. If there is a difference in the two
readings, your instrument needs adjusting by a David White
service facility.
If you have questions about checking for calibration, contact
David White or a repair facility. All actual adjusting of the
instrument must be done by a qualified service facility.
For your records
Date purchased
Model No. ❑ L6-20 ❑ LT6-900
Serial No.
For owner identification, please complete and mail the attached registration card.
Limited Lifetime Warranty
David White ("Seller") warrants this David White optical instrument to
be free from defects in material and/or workmanship. If, upon inspection, this instrument shall be proven to Seller's satisfaction to be defective, it shall be repaired or replaced, at Seller's option at no charge and
returned to the original purchaser ("Buyer"), transportation prepaid.
This warranty is not transferrable. Seller's sole obligation and Buyer's
remedy hereunder shall be limited to such repair or replacement with
these provisions:
1. The instrument is returned properly packaged, transportation prepaid
and insured by the Buyer to David White accompanied by proof of
ownership (copy of sale or receipt).
2. The instrument, upon inspection of Seller, is determined to be defective due to material and/or workmanship and is in original condition,
excepting only ordinary wear resulting from normal usage.
Limitations and Exclusions
1. The foregoing warranty does not apply to David White instruments
subjected to negligence, accident, improper operation or maintenance
or storage; instruments damaged by transit or circumstances beyond
Seller's control; instruments modified or damaged due to unauthorized
repairs made by other than David White or authorized David White service center personnel.
2. The foregoing warranty does not apply to instrument accessories or
include general maintenance and service such as cleaning, lubrication
or adjustment (i.e. calibration) of this instrument unless required as a
result of a material or workmanship defect.
If, upon examination of instrument, Seller determines that additional
repairs or services not covered under this warranty are required, Seller
shall notify Buyer of such charges and will proceed with said services
or repairs only after authorization is received from Buyer.
3. The foregoing warranty does not apply to David White instruments
damaged in transit to or from David White or a David White authorized
service center.
Corporate Office
David White
P.O. Box 359, Watseka, IL 60970 USA
Printed in U.S.A.
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