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<p>Strangely we had a similar situation when we submitted a device
for Electical checks.</p>
<p>They wanted to apply a voltage far in excess of the design, to
see if the capcitors failed as they should.</p>
<p>We said no as the supply was already tested, it was enclosed so
any capacitor rupture was contained and the test was for a
component rather than the device.</p>
<p>You should have seen the issues they had with SWA cable. :)</p>
<p><br>
</p>
<p>Designing devices for very high shock loads is an art and
requires consideration during design stage along with component
selection<br>
</p>
<p>I would suggest using an accelerometer to determine what sort of
shock loads are being experienced along with the tumble dryer
test.</p>
<p><br>
</p>
<p>Mark<br>
</p>
<br>
<div class="moz-cite-prefix">On 19/10/20 13:18, Stephen Irons wrote:<br>
</div>
<blockquote type="cite" cite="mid:I6AFIQ.BRR64XVP7JVX1@irons.nz">
<div id="geary-body" dir="auto">
<div>We have just had a discussion about whether the test
'finds' or 'causes' the failure, and have concluded that the
statement was meaningless, because there was no specification
about expected behaviour.</div>
<div><br>
</div>
<div>For example, we want to test that a device input works
correctly at its maximum specified operating voltage. <font
color="#ff0000"><b>The test is to apply 220 V to the device
input. After the test, the input no longer works. Is this
a failure?</b></font></div>
<div>
<ul>
<li>if the input was rated for 12 V, no it is not a failure
- the test exceeded the design specification, and we
should change the test.</li>
<li>if the input was rated for 500 V, yes it is a failure -
the test was within the specification, and we conclude
that something is wrong with the unit under test; it might
be a design issue or a manufacturing issue</li>
</ul>
<div>Our response to the client was essentially that: we have
found a test that makes devices fail in the same way that
they are failing in the field. However</div>
<div>
<ul>
<li>there was no design specification for that parameter</li>
<li>we don't know whether the failing devices are being
used within the design specification for that parameter</li>
<li>we don't know whether our test is within the design
specification for that parameter</li>
<li>as a result, we don't know whether the problem is a
test issue, a design issue or a manufacturing issue</li>
</ul>
</div>
<div>For interest, the parameter is 'shock and vibration'. The
test is to load a number of known-good units into a
vibration chamber (essentially, a tumble-drier with the
heater turned off), run it for a few hours, and see how many
still work after that.</div>
</div>
<div><br>
</div>
<div>The result: 70% failed after 4 hours, and the devices are
in a similar failed state to failures in the field.</div>
<div><br>
</div>
<div>But we have no idea what level of shock and vibration the
units are experiencing in the field, or whether our test is in
the same ballpark as that, or whether either of these are
close to the (unknown) design limits, or whether the
manufacturer is using a part that does not meet the design
criteria.</div>
<div><br>
</div>
<div>Stephen Irons</div>
</div>
<div id="geary-quote" dir="auto"><br>
On Sun, Oct 18, 2020 at 22:39, Marshland Engineering
<a class="moz-txt-link-rfc2396E" href="mailto:marshland@marshland.co.nz"><marshland@marshland.co.nz></a> wrote:<br>
<blockquote type="cite">
<div class="plaintext" style="white-space: pre-wrap;"><blockquote><blockquote>But we now have a repeatable test that causes the failure.
</blockquote></blockquote>
I'd find a new test!!!
I'm sure you mean 'But we now have a repeatable test that finds the failure.'
Cheers Wallace
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