Alex,
It all depends on how the results are used. If we compare one stove to
another or two different labs are doing the testing then, to be fair to
the stove maker, we should use calibrated equipment and QC thats to our
standard. Measuring CO (for example) in air to see if it passes a
standard we should use calibrated equipment. But if in house and looking
at changes it matter less.
Its fairness in testing that I think important. How great a stove is may
be equal to how bad the equipment used in testing was. We can't put
together a catalog of stoves that includes results to be used in
picking the best one for an area until we get fair testing to compare.
Thats all down the road - I hope...
Regards
Frank
Alex English wrote:
Dear Frank and all,
As a old CO testing hack I wished for scientific calibration and
settled for functional repeatability. Aside from zero I had a kerosene
lamp that I move through a range of clean flame heights (2,3,4 cm) and
see how O2 and CO changed. Unfortunately all I am sure of is that they
had good correlation with each other, good for a hack. Aside from that
we had our oil fired Riello burners on our boilers which also behaved
with admirable consistency, similar to the kerosene lamp, only not
portable.
I suppose some might think this is useful advice and others are
thinking "stop! This is what we don't want"
Practically yours,
Alex
On 10/26/2010 5:23 PM, frank wrote:
Dear Crispin and all,
We have Zero for one calibration, we have range, linear response and
detection limit. Working in a lab one can get overly critical of
reported values that does not go through all the steps at the time of
testing. I realize not as important for much of the stuff we do but if
we are to place values on CO in the air, set limits and the such, we all
need to be using calibrated equipment.
Does Emerson provide the supply gas? or use electrical signal for the
calibration? I suggest it can only be done using real pure gas.
Regards
Frank
Crispin Pemberton-Pigott wrote:
Dear Frank
I think the calibration is needed now and then. Real calibration
against a calibrated source.
Daily, we look for how it treats air. I like Philip Lloyd's practise
of removing the probe from time to time to see if it has CO go to
zero. It is rare for cells other than CO to have problems. CO cells
can get saturated and report high for quite a long time (an hour).
In UB we use air as a start and finish calibration. The instruments
are so accurate it is amazing. The CO2 will happily report 17% and
after 5 hours of zipping up and down, settle on air being 0.039%
within a few seconds.
However, the issue of absolute calibration is important enough that
Emerson offers an attachment that will recalibrate each time the
instrument changes ranges!
Regards
Crispin
--
Frank Shields
Soil Control Lab
42 Hangar way
Watsonville, CA 95076
(831) 724-5422 tel
(831) 724-3188 fax
[email protected]
www.compostlab.com
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