Temp/RH one to one Calibration

[OperaDiva1]

Hi Guys,
I'd like to know if anyone can provide a good explanation as to why it is legal to do a one to one comparison in order to calibrate an OMEGA ithx-M.  I have to explain to a bunch of scientists why this is considered a legal calibration.  I have a tech.  here performing calibration on the units that can be removed from their mountings, but some cannot.  Most of them he is doing in a chamber with standard salts and a veriteq.  The units that cannot be removed from their wall mountings, he's going to do a one to one with the veriteq.  So, the question is:Is this considered a legal calibration because he's using a standard that has been calibrated to a higher accuracy standard, has traceable history, and has uncertainties that have been accounted for and documented.  The veriteq 2000 would be used as a transfer standard would it not? Thanks for the answers.
OperaDiva1  :-)

[MRD]

You might want to contact Gregory Strouse, [email protected], he's on the Thermometry Group Staff at NIST, he's a great guy, very personable.

[WestCoastCal]

I'd think that provided you have an approved calibration procedure, traceable standards, uncertainties and/or test ratio's stated it's a legal cal.  The only problem is determining an in or out of tolerance as received condition, with a 1:1 cal, guardbanding is not on option (A weak argument can be made if the UUT measured dead nuts nominal with the error correction of the cal standard applied with uncertainties added to form an acceptance criteria).  Hopefully your calibration management system as received condition has an option such as "reference calibration, client to determine adequacy of calibration".  If this is ok with your customer I recommend you document it for the future.  Years ago, I've heard use of state of the art calibration.  Does anyone still use the statement "state of the art calibration"?  After re-reading what I wrote, I have no easy answer, thus going back to the customers acceptance of the calibration.

[metrologygeek]

We have over a hundred of these in our inventory, including 20 here in our lab.  We have applied a group derating to them of 3°C and 5%RH for the very reasons you cite, as well as their history.

[Wilk]

The veriteq 2000 would be used as a transfer standard would it not?

To be used as a "transfer standard" something must have the resoultion, and short term stability required to transfer the UC of one unit to another.   The vertec you mention doesn't fill either one of those requirements.   Thats just a 1:1 cal from the way I see it.   The uncertainty of the standards used to calibrate it may be irrelevent if it doesn't have the resolution or to resolve the true value of the reference standard used.

As far a legal goes, that could be anything.   You could tell the client that the probe is 6 inches long, if you measure it with a tracable ruler, write a procedure, and the client buys off on it.   

Whats more important is that if the clients use of those instruments actually needs a better uncertainty than you can provide at a certain confindance level. 

[OperaDiva1]

Hi Everyone,
I wanted to thank you all for your "very" valuable input.  I also wanted to let everyone know that I cannot begin to tell you how much I value your help and this web site.  I'm still learning my way around it.  I wanted to give everyone a little back ground about myself, even though we're supposed to be in cognito',  because I probably will be coming back to the site often in search of help.  I have no peers here where I am working, but have more knowledge, as limited as it is, about Metrology than anyone else on the entire campus.  So, I'm asked to set policy and be the subject matter expert in the Space Quality Dept.  here. 
I went in the Army for Satellite Communications and became a ground terminal technician and instructor.  When I got out of the Army, I stayed in electronics, raised a couple of beautiful kids, help put my husband through engineering school and kept working in electronics in one form or another.  I've worked at Navy depot level overhaul facilities on transceivers, worked a bench troubleshooting etc, and then was lucky enough to get on the job training in Metrology.  I then worked in some cal labs afterwards and loved it! I am one of those who always wished I could have gone to the PMEL schools.  There's a lot in between, but it's too much detail for here.  Well, now it's later in life, and I'm still involved in electronics, but I don't get to work a bench much.  Now, it's all head knowledge my employers are after.  But, I'm terribly rusty with Metrology and as I've said, I have no other peers.  I also am having trouble finding reference books/material that I can use.  I'm seriously thinking on going back to school to roll my associates into a mechanical eng.  degree and try to pick up the Metrology certification at one of the college's that offers it, but that will take time.  So, I'm hoping that you guys would basically be my mentors, would be patient when I come back with questions about what is patently obvious to you guys and would help refer me to books and/or resources where I can continue to develop my skills.  It's been hard to find books that deal with Metrology terminology, etc.  I'm working hard to come up to speed and hope to continue grow in this field. 
Well, I just wanted to be up front and honest with you guys so you won't become impatient if I ask too many questions.  Again, I want to thank you so much for your input and this web site.  :-) Susan a. k. a.  OperaDiva~yes I do like to sing!

[beadwork]

At my company we use a Vaisala HM70 with a HMP77 probe whch is accredited calibrated by Vaisala to ±1 %RH.

Mike Boothe
ASQ Sr.  Member, CCT
Quality Manager
Cal Lab Co, Inc.
17035 Westview Avenue
South Holland, IL 60473
800-373-1759 - 708-596-5802 FAX
quality@callabco. com - www. callabco. com
ISO 17025:2005 Accredited by A2LA for calibration 1336. 01, 1336. 02
31 Years in Business

[OperaDiva1]

Hi Mike,
Thanks for your input! I'll write this down as a reference piece of gear to compare to.
Pretty Cool that you're in Illinois.  That's my home state!
Have a great weekend!
Opera Diva!  :-)

[MFrisz]

There are also rental companies that you can go through and rent the Visala or similar so you can perform this calibration.  They will usually come with an accredited calibration.   Masy systems is one of these companies.  John Massielo is the Owner and is a good resource for humidity measurements.   www.masy.com

Mike