A. Whenever a change in material presentation that
is sufficiently different from the original material or for
maintenance purposes around every 12 months to
ensure reliable readings.
A. The Moistscan has proven itself on conductive
materials, however it is best to check with one of our
engineers to ensure you are going to have the
best product that suits your requirements. We may be able to
assist with one of our NFA enabled Moistscan
analysers if the material is highly conductive.
A. Moistscan measures TOTAL moisture. Free moisture
is moisture that can theoretically be dried off the material
by a drying process. Inherent moisture is
moisture that is bound within the material being measured.
TOTAL is the combination of both.
A. The precision is based on the type of material to
be analysed and how amenable it is to using a microwave
technique. Some materials can result in 0.1
precision.
A. The reliability of original lab samples, the
presentation of the material (if inconsistent) and some
environmental factors. All these factors can be
overcome by providing as much information as possible so our
engineers can find a suitable installation point
where theses factors can be reduced or eliminated.
A. Magnetite concentrate and magnetite ore have
proved to be difficult applications for the standard
MoistScan® transmission technology. This is
chiefly due to the magnetic nature or magnetic permeability
of the product. The magnetic permeability is the
degree of magnetization of a material in response to a
magnetic field.
Put simply, the microwave transmission signal is
largely affected by the water within the Ore/Concentrate
BUT unfortunately also affected by the magnetic
permeability of the product. This is a problem because we
cannot distinguish the moisture changes from the
magnetic permeability changes.
Recently Callidan has developed an analyser which
will overcome these difficulties. We call it NFA
(Near Field Analysis) but it is simply a direct
measure of the magnetic susceptibility and microwave
response (via reflection) of the material. It is
called “Near Field Analysis” because the analysis zone
will only penetrate the lower portion of the
product upon the conveyor and NOT all the product like our
previous transmission technique.
A. Consistency and better accuracy over other
types of methods. eg: NIR (near infra red), microwave
technology is safe and reliable,
unaffected by material presentation & colour variations, etc.
For full details
click here
A. Precision is a gauge
of the deviation within a set of measurements. In this case, it
is the repeatability
of moisture content measurement. It is
expressed as the standard deviation of a number of measurements
of the same sample.
A. Accuracy is a gauge
of the deviation between a measurement and the value of the
property being
measured. In this case, it is the deviation
between the MoistScan® results and the laboratory results for
a set of samples. It is expressed as the
standard deviation of the differences between analyser and
laboratory results.
A. The more samples
taken, the more confidence placed in the calibration. Many
statistical measures have
little confidence below sets of less than
30 samples. If taking 30 samples is not feasible, then as many
samples as can be taken. To increase the
level of confidence from a set of samples, they should be
analysed more than once.
A. Under normal
circumstances the answer would be no. However, products with
high temperatures
(above 60º C/140º F) can be compensated
with the use of the optional temperature sensor unit.
A. The microwave
technique penetrates through all the product material on the
conveyor, so there is no
adverse effects of product segregation.
This segregation may have an affect how representative samples
taken from the conveyor are.
A. No, steam has a very
low dielectric constant compared to liquid water. As the
MoistScan® uses a
patented process for dielectric
discrimination, the moisture readings will not be affected.
A. Using a compressed
air stream to remove condensation is one option or alternatively
install the analyser
at another location away from the steam
source.
A. No, the microwave
antenna of the MoistScan® are usually unaffected by surface
dust. They are also
robust enough to withstand normal wash down
procedures that are common on many processes.
A. Under normal
operating conditions, the MoistScan® should not require
re-calibration unless product
presentation is significantly altered.
However Callidan do suggest some check samples be taken every
three months to confirm accuracy.
A. No, The microwave
power emitted from the lower antenna is approximately 10 mW (10
dBm), which is
significantly less power than most mobile
(cellular) phones.
A. The MoistScan®
MA-500 On-Belt Moisture Analyser is designed to use low level
non-ionizing microwave
radiation. The microwave power emitted from
the MOISTSCAN MA-500 is less than 10 mW (10 dBm).
This complies with AS/NZS 4268 which
specifies the maximum Equivalent Isotropically Radiated Power
(EIRP) for short range radio equipment.
Furthermore, this radiation level exists directly between the
two
antennas, which in almost all cases is
inaccessible due to the conveyor belt. Microwave radiation
further
than 1 m from the analyser is virtually
undetectable.
A. Using the
ultrasonic depth sensor on the MoistScan® the analyser can
be programmed to ignore
bed depths that exceed the maximum
bed depth for the product. The unit will automatically
re-commence
analysing once the bed depth is back
within the normal operating range. This answer also applies to
bed depths that fall below a
pre-programmed minimum depth.
A. The MoistScan®
measures free moisture. Inherent or crystallised moisture is not
measured. Callidan are
currently investigating techniques in
measuring inherent moisture. ASK US!
A. The MoistScan®
is provided as standard with these outputs:
2 x 4-20mA
2 x discrete digital inputs.
Modbus over RS-232 (ASCII)
Modbus over RS-485/Ethernet
(optional)
A. The MoistScan®
has proven itself to be reliable, repeatable and much more cost
effective than any
similar Nucleonic based moisture
analysers. Other advantages are: No radioactive sources in the
MoistScan®, which means no red tape
associated with getting radioactive sources government approved
and ultimately it is a safer more
environmentally friendly gauge.
A. The ultrasonic
depth sensor is satisfactory for most applications that involve
moderate variations in
bulk density. It is, however, limited
in applications that have very dense material combined with
large
variations in bulk density. In these
applications we take an input from a weightometer or similar
mass
throughput sensor to compensate for
the density effects.
A. The MoistScan®
employs a patented technique that differentiates it from its
competitors. Using a
combination of attenuation/phase
shift of the microwave signal and dielectric discrimination
techniques, the MoistScan® will
provide the end user with consistently reliable results.
EXAMPLE:
Fine coal typically has a dielectric
constant of between 2 to 4 compared to the dielectric constant
of water of 80.4. The variation of
water within the coal results in a large variation in the
combined
dielectric constant which may then be
measured by monitoring the change in the microwave signal. Both
the change in velocity (phase shift)
and the change in power (attenuation) of the received microwave
signal are affected by the change in
the dielectric constant of the analysed material. The microwave
measurement is affected mainly by the
excitation of free moisture molecules rather than many other
types
of materials, due to the extremely
high dielectric constant of water.
A. Ideally the
presentation of the material should be uniform; however slight
changes in presentation should
not pose any problems with
maintaining reliable results. If material upon a conveyor is not
centred
correctly, or is badly profiled, then
a leveler bar could be installed to improve the material
profile.
A. Factors that
influence highly accurate results are: Minimal spread of
moisture range. (The tighter the range
the more accurate the instrument will
be), even material presentation on the transport medium,
representative sampling, careful
handling of samples and prompt analysis. The analysis procedure
should
consume all of the sample.
A. The microwave
principle employed by the MoistScan® is a full penetration
technique which means the
product is fully scanned for moisture
content as opposed to NIR, which is basically a surface
technique
using an infra red light beam. The
results of a NIR gauge is adversely affected by colour
variations, ambient
lighting, and presence of dust and
temperature variations. The MoistScan® is unaffected by any of
these anomalies, thus the MoistScan®
will give a more accurate indication of the free moisture within
the
product.
A. Yes, by using
multiple calibrations in the MoistScan® (up to 4 separate
calibrations can be utilised by
default with the option of 50
calibrations in total) it is as easy as switching a remote
calibration switch
either from the control room or on
the MoistScan’s control panel for different products.
