WNIP Mar Apr 19.2 Digital

4
Next generation hand-held oscilloscope
19.2
After 17 years of leading the
20MHz and 40MHz hand-held
industrial oscilloscope category,
Fluke models 123, 124 and 125
ScopeMeter Test Tools are being
replaced by new models 123B,
124B and 125B.
The compact ScopeMeter®
120B Series, is the rugged
oscilloscope solution for industrial
electrical and electro-mechanical
equipment troubleshooting
and maintenance applications.
It’s an integrated test tool, with
oscilloscope, multimeter and highspeed
recorder in one instrument.
The ScopeMeter 120BSeries also
integrates with Fluke Connect®
mobile app and FlukeView® for
ScopeMeter software to enable
further collaboration, data analysis
and archiving of critical test
information.
The 120B Series Industrial
ScopeMeter Test Tools include
innovative functions specifically
designed to aid technicians’
troubleshooting. Waveforms
can be displayed with Connect
and View. Fluke’s IntellaSet
technology triggers and setsup
technology and allows for
automatically view related
numerical measurements, all
without the need to make manual
measurement adjustments. With
Recorder Event Detect capabilities,
elusive intermittent events are
captured on repetitive waveforms
up to 4 kHz and logged for easy
viewing and analysis.
Other features of the Fluke
120B ScopeMeter:
• Dual-input digital
oscilloscope and multimeter
• 40 MHz or 20 MHz oscilloscope
bandwidth
• Two 5,000-count true-rms
digital multimeters
• Dual-input waveform
and meter reading recorder for
trending data over extended
periods
sales@comtest.co.za
Batching with load cells
The first task in preparing a
concrete mixture, is batching
raw materials. Batching means
collecting raw materials,
either by using methods of
weighing, checking volume or
by a combination of the two.
During batching, there are
certain permissible tolerances
that are typically part of project
specifications and/or noted in the
“NPCA Quality Control Manual for
Precast Concrete Plants”. A load
cell, together with a read-out,
is used to accurately weigh the
correct amounts, giving you a
desired mixing pattern (referred
to as the mix design), which
assists in mixing the concrete in
the desired consistency.
Cementitious materials are
usually stored in hoppers/silos,
with the material is loaded into
the hopper either by means of a
screw drive (or auger), a pneumatic
system, or a gravity feed chute,
loading from above. As an aside,
it is important to make sure that
should an auger be used, the item
is specifically designed for use
with cement. Retrofitting old
grain augers, is not advisable, as
this can lead to excessive wear and
less that optimum performance.
Lastly, physical inspections of
the silo should be done routinely.
By using load cells to weigh the
content of the hopper, an accurate
measurement can be done of
the contents of the hopper/silo,
and maintenance issues, such as
water leaks or holes, can easily
be detected (the weight of the
content will change).
Water is batched by either
volume or weight. Flow meters
are used as a measuring device to
quantify the volume of water that
passes through the valve. One
concern with this method is that
flow meters cannot distinguish
between air and water. Leaky
valves also allow water to dribble
through when closed. Considering
the importance of the watercementitious
ratio, it is advisable to
rather use load cells, as measuring
weight rather than flow, is a
much more accurate method of
quantifying the amount of water
used.
Admixtures are typically
batched by volume through a
dispenser. Usually an admixture
supplier, will provide the dispenser
at no cost to the producer. It
is recommended that you
investigate this option. Dispensers
reduce the likelihood of improper
dosing. Be sure to introduce
admixtures into the concrete mix in
accordance with the manufacturer’
recommendations.
Aggregates are batched most
commonly by weight. Whether
in a hopper, on weigh belts, in or
directly from storage bins, load
cells are used to measure the
weight of the material. The most
common method used is weigh
belts. However, “weigh belt” is
a misnomer. A true “weigh belt”
weighs while it is moving. In most
batch plants, Live Bottom-Weigh
Hoppers (LBWHs) are used. An
LBWH’s belt is stationery while
weighing aggregates. This type of
belt may be started under load to
move the weighed aggregates to
a transfer belt, hopper or skip hoist.
Overall, accuracy in all of the
above processes can be improved
by installing load cells. By weighing
each component, an accurate
measurement is done of the
batched material, and a desired
consistency can be achieved in a
continuous time-saving method.
glen@loadtech.co.za