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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