Hi

can anyone give me the information about the relating standard for calibration of conductivity meter.

Muhammad Asif

It's been quite a while since I've calibrated conductivity meters, but the method I seem to recall is using buffer solutions. I believe there is a company in Houston TX that is accredited to produce those buffer solutions. Since this is not a commercial site, I'll also say that I am not recommending them, that is the only accredited vendor I know about. You could probably check the accreditation search engines such as at A2LA, etc. to see if there are others.

Also, I believe (per my recollection) that the buffer solutions are temperature dependent, so monitoring solution and air temperature may be a part of the procedure.

Please consider the above as general information to help steer you in the right direction.

Dear Jerry Eldred,

well infact i am looking to quote the standard in the Reference of the Calibration procedure for ISO-17025 . if u also know about the standard that covers standards like astm, bs,din etc.

With Best Regards

Muhammad Asif

There are different standards, depending on whether the conductivitiy is the solid resistive kind or a solution.....

For ASTM, the best source is the ASTM website http://www.astm.org

Hershal

Dear Jerry,

Got this small issue on the frequency of calibration. I am currently working in a small company with vernier calipers, digimatic calipers, digital weighing scale, digital hanging scale, tri-axial accelerometer, steel rules and measuring tapes.

In order to save costs, a lot of the abovementioned equipments are scheduled for calibration every 48 months. Others 12 months.

My question is: What is the standard for frequency of calibration and where can I find a copy of this standard without paying?

Pls advise.

I don't know of a single source for this information (although there could be, as my specialty is not dimensional instruments); although I've calibrated calipers, micrometers, and many basic dimensional instruments. Could be that ASTM or ANSI has some recommended intervals.

There are a few possible answers:
1. GIDEP or MIDAS (both Government based calibration information resources) may have something. MIDAS, I recall has a document listing their calibration intervals. However, to have access you need to have a government contract.

2. Manufacturer's intervals. If you use one manufacturer as your primary source for a high percentage of these instruments (or even two or three mfrs), contact them and ask their recommended intervals (if they are not already published in their manuals.

3. Interval analysis. Look at your out of tolerance history. You can pretty simply calculate in-tolerance/out-of-tolerance proportions. Take the total number of calibrations, and calculate the percentage of out of tolerance occurrences. There is a free software package call A3 Interval Tester (search on Google or other search engine for it - or email me separately at jerry.eldred@freescale.com and I can help you locate it - I'm a bit of a web search wiz). With this software (based on NCSLI - National Conference of Standards Laboratories International's) Recommended Practice RP1 for the establishment and adjustment of calibration intervals, you can determine what your intervals should be based on past history.

On that topic ('Rabbit Trail'), there are a number of methods and criteria for setting and adjusting your calibration intervals. There is the "fixed" method (which I believe you are using), wherein you set a given interval based on some criteria (mfr recommendation, borrowed from other source, etc.), and there are a number of adjustable intervals. You can really set your intervals where ever you want (based on what ever criteria you have to meet). The object is that you have something acceptable to meet your criteria (this could be ISO17025, FDA, FAA, DOD, internal quality requirements, etc.).

Initial intervals may be set based on the above. To adjust them, you can use a number of methods. Perhaps the most popular is the method I described above. There are some other more complex methods where (for example) you evaluate actual measured values and statistically predict when the instrument should go out of tolerance. Even with our large inventory, this is more than I am personally interested in doing. There are other methods and criteria as well.

My recommendation would be to contact the manufacturers to find out their recommended intervals (if they make the recommendation), get the A3 interval test software, and review your calibration history.

As I am currently working on interval evaluation (86,000 calibrations) this topic is fresh in my mind. Please feel free to send me any questions you may have.