Electronics > Metrology

The search for PPM and PPBs has to stop.

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TimFox:
As I posted before in another thread, I was once confused during an installation in UK where the local engineer asked me about a wire size, using "mils", which I knew was not 0.001 inch.  Unfortunately, he did not mean "mm", he meant "mm2".

Conrad Hoffman:
IMO, the demise of ppm is old news. I also lament the loss of micron, though it's still in so much common use that I don't think anybody's going to change anytime soon. In the US, a micrometer is a thing you use in the shop to measure with. I think angstrom is fading away but is still acceptable in the "outside SI" list at NISt.

mendip_discovery:

--- Quote from: DH7DN on December 07, 2021, 10:46:17 pm ---Such revision don't happen "out of the blue". Either there have been some inconsistencies or contradictions in context of ISO/IEC 17025:2018 (Section 7.8 ) or there have been inconsistencies in reportings of measurement results or applications of CMCs.

--- End quote ---

I think it may be because it doesn't state what that ppm is referring to. For example, we may have a 10 mV to 100 mV range with an uncertainty of 23ppm + 12μV the ppm can be seen as unclear if it relates to mV or μV. Plus ppm is an English acronym and possibly they would like to reduce them.

Lab 45 (6.10) has this to say about the use of %

--- Quote ---Particular care should be taken when the unit itself is normally expressed in percentage terms;
examples are relative humidity (%rh) and amplitude modulation (% AM). For example,
50 %rh ± 10 %rh means the boundaries are 40 %rh and 60 %rh, whereas
50 %rh ± 10 % means the boundaries are 45 %rh and 55 %rh.
 
Under circumstances of this nature the presentation of the CMCs must be such that there is no
ambiguity in interpretation.
--- End quote ---

The last bit being the interesting one. Its interesting that electrical is used as the example so it clearly is some sort of comment on them. Though as a mech lab that is going for some 17025 stuff I think the below quote may give a reason for the mud slinging that might be going on. ;-)

Lab 45 6.17

--- Quote ---In dimensional calibration, the schedules of accreditation for the calibration of basic dimensional
measuring tools and equipment have historically reported a CMC for parameters most relevant
to  end  users.  This  method  however  does  not  provide  transparency  with  regards  to  auxiliary
measurements  such  as  flatness  and  parallelism  of  micrometer  measuring  faces  etc.  These
additional measurement techniques shall be listed on the schedule of accreditation along with
the corresponding measurement uncertainty.
--- End quote ---

For years labs only needed to say the error of length and not mention the capability for flatness or squareness. It is a bit like having a multimeter calibrated and the only Uncertainty quoted is for the Voltage.




--- Quote from: TiN on December 08, 2021, 03:41:45 am ---PPMs must live on. Not until inch and other nonsense units go away  :-DD

--- End quote ---

Its interesting as officially you splitters have been using the metric system for a while, but for some reason subconsciously you still want to be back under British Rule  >:D


--- Quote from: TimFox on December 08, 2021, 02:42:50 pm ---As I posted before in another thread, I was once confused during an installation in UK where the local engineer asked me about a wire size, using "mils", which I knew was not 0.001 inch.  Unfortunately, he did not mean "mm", he meant "mm2".

--- End quote ---

Yeah, we use mil as an abbrev for mm. So "shave a few mils off that" and "I have some 2 mil wire" are common. I do get confuddled when you get places selling wire in Amperage, "yeah that is 12 amp wire". AWG, mm2 and CSA at times do give me fun afternoons exp when a customer makes up some crimp samples for me but assumes I know the size of wire just by looking at it.



--- Quote from: Conrad Hoffman on December 08, 2021, 05:23:29 pm ---IMO, the demise of ppm is old news. I also lament the loss of micron, though it's still in so much common use that I don't think anybody's going to change anytime soon. In the US, a micrometer is a thing you use in the shop to measure with. I think angstrom is fading away but is still acceptable in the "outside SI" list at NISt.

--- End quote ---

So if PPM and PPB are old news then why are we getting people hear singing and dancing about how their meter is good to 1ppm.

Vtile:
What is so sacret in ppm and ppb and ppt and what all there is. I will not cry after those. Why not to use proper units, they are rather usable.

TiN:
Same goes to percents, it is just convinience when you only want a ratio between similar measurands, instead of dealing with 9 digits after decimal centipedes.

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