468 CHAPTER 8. LABORATORY MEASUREMENT AND ANALYSIS
start to exhibit strong nonlinearities, at which time the derived sea surface
elevation “measurements” begin to deviate from true values.
Recording data can be as elementary as writing observed measurements
in a log book, or it can be as advanced as automatic (and extremely rapid)
collection of massive amounts of electronic data using the very latest in
computer technology. Analog and digital data recording are the primary
forms of recording in hydraulics laboratories. An example of an analog
recorder is the strip chart where continuous data are recorded on the chart
with ink pens. Analog recorders are rapidly being replaced by equivalent
digital recorders which convert analog data into electronic digital form for
storage on magnetic media (computer disks, tapes, etc.) These recorders
can provide a visual output similar to an analog recorder, and they have
the added advantage that the data are in a convenient form for additional
data analyses.
In electronic instrumentation, signal conditioners are used to relay the
measured signal to the recorder and/or to supply precise voltage levels to
the instrument sensor. Signal amplification and other signal manipulation
are sometimes part of the signal conditioner. Each particular sensor has its
own specialized signal conditioning requirements, and these components are
typically matched during instrument manufacture. The chief requirement
of the signal conditioning unit is that it manipulates the measured signal
with a minimum of distortion.
Instrument control units facilitate easier instrument configuration and
operation in the laboratory. They also can provide safeguards and alarms
to protect the instrument from incorrect inputs (such as high voltages) and
various fault detection techniques to help assure that only high-quality measurements are recorded. Although control units make it easier to operate
an instrument and obtain data, it is still the responsibility of the investigator to make certain that the equipment is being correctly operated by
knowledgeable persons.
Instrument Operation
Correct instrument operation is just as important cis selecting the right
instrument. The following suggested steps for setting up and operating an
instrument were given in Hydraulic Laboratory Techniques (1980):
1. Carefully check for potential grounding problems in electronic instruments, or any other electrical or mechanical
interactions that might not be detected in the instrument
calibration procedure. Line noise (50/60 Hz) is the bane
start to exhibit strong nonlinearities, at which time the derived sea surface
elevation “measurements” begin to deviate from true values.
Recording data can be as elementary as writing observed measurements
in a log book, or it can be as advanced as automatic (and extremely rapid)
collection of massive amounts of electronic data using the very latest in
computer technology. Analog and digital data recording are the primary
forms of recording in hydraulics laboratories. An example of an analog
recorder is the strip chart where continuous data are recorded on the chart
with ink pens. Analog recorders are rapidly being replaced by equivalent
digital recorders which convert analog data into electronic digital form for
storage on magnetic media (computer disks, tapes, etc.) These recorders
can provide a visual output similar to an analog recorder, and they have
the added advantage that the data are in a convenient form for additional
data analyses.
In electronic instrumentation, signal conditioners are used to relay the
measured signal to the recorder and/or to supply precise voltage levels to
the instrument sensor. Signal amplification and other signal manipulation
are sometimes part of the signal conditioner. Each particular sensor has its
own specialized signal conditioning requirements, and these components are
typically matched during instrument manufacture. The chief requirement
of the signal conditioning unit is that it manipulates the measured signal
with a minimum of distortion.
Instrument control units facilitate easier instrument configuration and
operation in the laboratory. They also can provide safeguards and alarms
to protect the instrument from incorrect inputs (such as high voltages) and
various fault detection techniques to help assure that only high-quality measurements are recorded. Although control units make it easier to operate
an instrument and obtain data, it is still the responsibility of the investigator to make certain that the equipment is being correctly operated by
knowledgeable persons.
Instrument Operation
Correct instrument operation is just as important cis selecting the right
instrument. The following suggested steps for setting up and operating an
instrument were given in Hydraulic Laboratory Techniques (1980):
1. Carefully check for potential grounding problems in electronic instruments, or any other electrical or mechanical
interactions that might not be detected in the instrument
calibration procedure. Line noise (50/60 Hz) is the bane