MEMS Digital Inclinometer System with Android
Instruction Manual
ICM0099A
35
same elevation in an earlier survey conducted at a previous date, it may mean that one of
the two readings in the + or - direction was not done properly, and the user will then be able
to repeat that same reading in order to restore the checksum to a similar lower value as in
previous surveys.
Checksum in A+/A- plane = A+ plus A-
Checksum in B+/B- plane = B+ plus B-
The checksum should be reasonably constant and of small magnitude, typically less than +/-
2 mm (0.08 in) and preferably less than +/- 1 mm (0.04 in). Large and inconsistent
checksums may indicate that a problem exists. However, the consistency of checksums from
survey to survey is more important than the actual value of the checksums. Checksum data
should be monitored during the survey as a check on data integrity. Note that high
checksums can be expected if a settlement coupling has been encountered, a checksum of
the order of +/- 4 mm or (+/- 0.16 in) would be reasonable at consecutive depths/couplings.
M
EAN
D
EVIATION
A+/A- mean deviation in the A+/A- plane = (A+ minus A-)/2.
B+/B- mean deviation in the B+/B- plane = (B+ minus B-)/2.
This represents the mean deviation at each depth, corrected for any systematic bias that can
be present in the inclinometer probe as the average of the two measurements opposed at
180 degrees cancel that bias.
A
BSOLUTE
P
OSITION
An absolute position value at a particular depth is the summation of mean deviations starting
from the bottom up to that particular depth. Absolute position is the profile of the access
tube with respect to the vertical axis in a given plane. Absolute position can also be
calculated
from the top down if required using Inclinalysis™ software.
I
NCREMENTAL
D
ISPLACEMENT
The incremental displacement is the difference in values of mean deviation between the
base file (first set of readings taken) and a compatible file (usually the latest set of readings)
at each depth.
This plot can be generated using Inclinalysis™ software.
C
UMULATIVE
D
ISPLACEMENT
The cumulative displacement is the result of comparing two sets of mean deviations, usually
the base file and the latest or comparison file. The profile represents the actual movement
(or displacement) which has occurred at all depths between the times that the two sets of
readings were obtained.
7
S
YSTEM
C
OMPATIBILITY
Regardless of the inclinometer system being used, it is imperative that the
probe wheels
be
placed at the same locations during each profiling of the borehole (this is not necessarily the
same depth marked on the inclinometer cable). Always use a consistent top reference, such
as the aluminum cable grip which is provided with all RST Inclinometer systems.
The zero-depth reference on the new RST Digital Inclinometer System refers to the midpoint
of the probe (between the wheel assemblies). This is the industry standard. The old RST
analog system is referenced to the uppermost set of wheels. Therefore, this
must
be taken
into account if the customer wishes to directly compare the two sets of readings. It is very
important that the data be within 4mm (0.25”). Otherwise, the data will not match, and the
comparison will not be valid.
