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Hello again.

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Welcome to installment five
in our video series

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providing best practice advice

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on geochemistry applications
with portable XRF.

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I’m Todd Houlahan.

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I’m joined by my colleague
Marcus Lake.

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Hows'it Marcus?

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Hows'it Todd?

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Today we’re going to be
talking about test times.

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Just how long do you need to test

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a sample to get the right result?

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Marcus, how do you
answer this question?

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Todd, as you know, during this series

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we’ve been repeating ourselves a lot

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in advising on your best practice

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for field portable XRF fluorescence.

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Testing times is a very
important part of that.

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In general I’d say minimum should
be ten seconds per beam

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and a maximum of about a hundred
and twenty seconds per beam.

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OK. Two things jump out at me there.

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There’s a big range between
ten seconds per beam

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and a hundred and twenty
seconds per beam,

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especially if we’re talking
about multiple beams.

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And two, what’s a beam?

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So how about I discuss the
question about testing times Todd,

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and you discuss the beams.

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Genius Marcus, as always.

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So Todd I’d like to start
the discussion

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about what is actually
impacted by test times

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when using your field portable XRF,

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mainly in relation to precision
and lower limits of detection.

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It’s all about statistics.

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The x-ray is gathering
hundreds of thousands

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of points of information per second
thus, for some users,

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a shorter testing time
might be applicable

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and for others a longer testing
time might be needed.

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Light elements, magnesium,
aluminum and silica

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are harder to measure aren’t they

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because they fluoresce more weakly
than the heavier elements?

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That’s right Dr. Todd.

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The elements, particularly
magnesium, aluminum and silica,

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in my experience,
with a low atomic number,

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will need a longer testing
time to test at or near

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the limit of detection
for our analyzer.

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Can you please explain how the beams

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are optimized on our analyzer?

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Sure. What’s a beam,
or a beam setting?

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Using different beams allows
us to optimize the instrument

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for different parts
of the periodic table.

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A beam is comprised simply
of the voltage of the x-ray tube,

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the current across the
anode of the x-ray tube,

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and some filtration that we
position in front of the x-ray.

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With these three things we
can optimize the analyzer

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for different elements and
our systems utilize options

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of one beam modes, two beam modes,
or three beam modes.

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And that’s all going on in the
front nose of the analyzer.

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So Todd how about
we show the users now

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exactly how it works
in geochem mode

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which uses two beams.

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Let’s do it.

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OK. To see which elements are
measured by which beam,

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from the main screen we can
swipe down from the right

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and tap on Element Suite.

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And here’s where
we have the information

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for this geochem two beam
setup that we have.

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Beam one is measuring
at forty kilovolts.

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It’s optimized for those elements.

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Beam two is running at ten kV

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and is optimized for these elements

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so it’s important you know which
elements are optimized for which beam

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so that if we need to make
changes to the test time

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we simply can do that by
changing the test times in here.

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And then back to the main screen

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and we’re ready to take a test,
it’s that easy.

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So another way I like to show
customers very simply

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how to achieve the optimum testing
time is by a simple XY graph.

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With X axis testing time
and Y being precision of XRF.

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Obviously, as you can see here,

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precision improves
over a longer testing time

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but the customer actually needs
to find their sweet spot.

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It could be a hundred and
twenty seconds down here

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or as little as ten seconds
sort of down here.

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Now let us show you an
example, within Excel®,

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of a customer achieving their optimum
testing time for their project.

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OK. Here’s an example of a customer

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who’s done an orientation survey
to optimize their test times

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under different scenarios,
ninety seconds,

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forty-five seconds
and fifteen second tests.

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Marcus, you know more
about this project than me,

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tell me more.

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Well Todd, interestingly enough,

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if we look at the comparison graphs

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we have a heavy element
and a light element.

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As we stated before, sometimes you
need a longer testing time

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for particularly light elements,
magnesium, aluminum and silica.

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If we look at the correlation
coefficients

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for both of those elements,
along with testing times,

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if we go from ninety seconds
to forty-five seconds

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to fifteen seconds we see
the correlation coefficients

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don’t actually change that much.

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Hence the customer is getting
higher throughput

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and achieving the data
results that they are after.

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I see there is a little
bit more scatter

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on the forty-five and
fifteen second tests

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over the ninety seconds but they
were willing to sacrifice that

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for the benefit of shorter test times.

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They were Todd. All they wanted
was faster throughput

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to get more tests in the day

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and faster quicker results
back to the laboratory

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for quicker turnaround times.

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And better productivity.

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Indeed.

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Good. That’s really
the key message right?

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Yes, not every methodology like this
is going to work for every customer,

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but the customer has to go away and
do this geochem orientation survey

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to work out their optimum testing
times that work for them.

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Yeah, yeah.

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OK Marcus, how should
we wrap this one up?

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What’s the message?

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So Todd, as you’ve just
seen from that example

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the customer should always
start with a long testing time

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and then bring that testing
time back to a point

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where they are comfortable with the
data quality that they are achieving.

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It’s not rocket science is it?

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No it’s not Todd but a customer
does need to take the time

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to work out what’s optimum
for their project.

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Just a little bit of work
at the beginning, right?

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Indeed Todd.

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OK. Next time we’re going
to talk about sample containers

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and the effect on the accuracy
and precision of the XRF

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when you’re using
different sample containers

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so hopefully you can join us then.

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And we’ll be seeing you mate?

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See you again Todd.