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TROPARI - Checking
for Accuracy and Working Conditions
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The
tests outlined below will allow a user to efficiently determine the
working condition of a Tropari Borehole Surveying Instrument. If
the instrument passes all of the sensitivity tests, then the accuracy of
readings will be within one degree of azimuth and inclination. |
| Sensitivity
Tests |
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- Figure #1
- View of instrument required for
sensitivity test #2.
- (Click on Fig #1 to enlarge)
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1.
Place the instrument on end (vertically) on a table and rotate the inner
frame. As most tables are not perfectly horizontal,
note whether the inner frame turns freely to seek the slope of the
table. If the inner frame stops
turning without seeking the slope, or
stops turning with obvious frictional retardation, then the lowermost end
pivot/jeweled bearing is injured. Turn
the instrument 180 degrees and repeat test on the end
pivot/jeweled bearing.
2.
Place the instrument on a horizontal surface near (and facing) the edge so
that the inclination markings and the protractor pin can be viewed
simultaneously with a magnifying glass (see
Figure 1).
If the instrument is placed on a table, it will be necessary to kneel on the
floor to observe this test. |
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CAUTION:
Hold onto the end of the outer frame so that the instrument does not roll
off the edge.
With
a finger, set the unlocked gimbal oscillating and note the readings when
the gimbal comes to rest. Repeat and note reading. If the two readings are
with ½ degree of each other, the sensitivity and accuracy of the
inclination readings are within factory specifications and the side
pivot/jeweled bearings are perfect. If the two readings are 1 degree
different, the inclination will still be more accurate than acid tests.
Greater differences indicate a need for servicing.
3.
Place the instrument on a horizontal surface and view the compass plate
from the top. Attract the compass with a piece of iron (paper clip, pen
knife etc.) so that the compass oscillates freely seeking magnetic north,
and if it repeatedly (2 or ore tests) comes to rest within 1 degree of
azimuth, the compass pivot/jeweled bearings are perfect.
These
tests can be accomplished in 5-10 minutes. Since accuracy in the Pajari
instrument is only dependent on its sensitivity, these tests effectively
determine accuracy |
Timing
Accuracy
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Figure
#2
Terminology
for Timing Tests.
(Click
on Fig #2 to enlarge)
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- Figure #3
- Correct procedure for starting instrument.
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1.
When the instrument is fully locked turn the timing ring gently toward the
timing readings (to the left). There must be a small amount of free
(effortless) rotation of the timing ring before it engages the internal
levers. Note where the setting mark on the timing ring (see
Figure 2)
comes to rest when resistance is encountered. If the setting mark is
coincident (+ or - 1½ minutes) with the first or zero timing mark, then
normal operating procedures are valid.
2.
Turn the timing ring so that exactly 10 minutes of timing has been
activated. At this time setting the
compass plate and gimbal should be free.
3.
Set exactly one hour of time on the instrument and note the time on a
watch. Start the instrument by oscillating it (see
Figure 3)
and make sure the timing ring has been returned to the extreme right-hand
position. After 50 minutes by the watch, gently rotate the timing ring to
the left until resistance is encountered. If the mechanism is running
time-true, the setting mark will indicate 10 minutes of time remaining, If
the mechanism is running slow there will be more than 10 minutes of time
remaining. If fast, less than 10 minutes.
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The
results of these tests will indicate whether the instrument is running
time-true. Timing errors do not affect the accuracy of the instrument other
than the possibility that the instrument may begin to lock on lowering or
not be securely locked during retrieval from the test depth. Corrections can
be applied to the setting time if the instrument does not run time-true as
follows:
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If
the setting mark is not at zero when the instrument is locked with + or
minus 1½ minutes (Test 1), add or subtract time required for a specific
time setting (add time if setting mark is past zero). If there is not
free movement of the timing ring before resistance is encountered when
the instrument is locked, the locked instrument may not be secure and
jarring may cause the readings to move. This problem has to be
rectified.
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If
the gimbal and compass do not rotate freely when 10 minutes of running
time is set, determine at what time setting these are free. This would
not be more than 1 or 2 minutes past 10 minutes (11 or 12 minute time
setting) if the instrument is otherwise functional. To correct, simply
allow 11 or 12 minutes for the instrument at its survey position.
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If
the instrument runs fast, say 3 minutes, then when one hour of lowering
time is required, set the instrument at l hour, 15 minutes (1 hour
lowering plus 10 minutes at rest plus 5 minutes error in running time).
A 30-minute lowering requirement would require one-half of 5 minutes or
a 2-½ minute in running time correction.
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correction if tests indicate instrument runs slow.
Although
the details of these timing tests may appear complex, the corrections
conveyed to the user would consist of a statement such as, for example:
Allow an additional ----- minutes for lowering and locking time.
This
simple statement would include all corrections and would seldom amount to
more than 5 or 6 minutes, but still necessary so that the instrument will
have definitely locked at rest during a test. For those surveyors that reach
the test depth well in advance of the last 10 minutes and wait for 5-10
minutes after time is up, these corrections are not necessary. |
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