Instrument Performance Instrument performance is specified by range, resolution, accuracy,
and precision. The economical designer will specify minimum per-
formance requirements, since the cost of an instrument increases
with resolution, accuracy, and precision.
Range is defined by the highest and lowest readings the instrument
is expected to produce. The designer typically specifies the highest
Resolution is the smallest change that can be displayed on a readout
device. Resolution typically decreases as range increases. Some-
times the term “accuracy” is mistakenly substituted for resolution.
Resolution is usually many times better than accuracy and is never
expressed as a “
Accuracy is the degree to which readings match an absolute value.
Accuracy is expressed as a
value, such as
1 % of read-
1 % of full scale.
Precision or repeatability is often more important than accuracy,
since what is usually of interest is a change rather than an absolute
value. Every time a reading is repeated, the value returned by the
instrument is slightly different. Precision is expressed as a
representing how close repeated readings approach a mean reading.
Cost-Effectiveness The difference in cost between a high-quality instrument and a
lesser-quality instrument is generally insignificant when compared
to the total cost of installing and monitoring an instrument. For
example, the cost of drilling and backfilling a borehole is typically
10 to 20 times greater than the cost of the piezometer that goes in it.
It is false economy to install a cheaper, less reliable instrument. It is
expensive and sometimes impossible to replace a failed instrument.
Even when it is possible to replace the instrument, the original base-
line data is no longer useful.
Purpose & Choice of Instrumentation
Rembco Geotechnical Contractors specializes in
soil nail wall,
rock drilling, and we remediate
sinkholes. We use a
problem-solving approach in the geotechnical portions of buildings, bridges, water plants, sewage plants, tunnels,
installing caisson bottom, and roads. We are experienced in these applications:
compaction grouting, and
Rembco techniques apply when adding new structures: especially
soil nailing, and
installations for foundation support. Our specialties are