Length and Mass standards 1

[mikeofBelAir]

As announced nearly a year ago, I am working at getting the lab here AASHTO certification. ( It was a long year with a LOT of field work--so not much progress in the lab....)
As I assemble the length and Mass standards to verify that our measurements, I need to know what precision I need.
The greatest precision on mass that we use is 0.01 grams---Would mass standards to 0.001 grams be acceptable? What "grade" would that be?
In length measurements, we sometimes measure to 0.001 inches, so the standards would need to be accurate and precise to 0.0001 inches? I( see that it possible to get gage blocks for anywhere from $100 set to thousands of $$. Even the cheapest sets claim to have a certificate trace4able to NIST. Have any of you tried those sets? What happened when the inspector came to view your lab? Were they OK?

 

[oldestguy]

Sorry to say in this room few if any test methods run soil tests to that precision. I suggest you post under mechanical engineer sites, such as machining metal. They may have more info than geotechnical engineers.

 

[Ron]

Mike...gage blocks are worthwhile if you take measurements with a micrometer or dial indicator. Stick with a brand name like Starrett, Mitutoyo or Brown and Sharpe.

10x on the precision is a good measure. Traceability to NIST is a must. Outside calibration of certain items (such as proving rings, load cells, etc.) is a necessity as well.

Documentation for these is key. Make sure all your equipment is labeled with a calibration sticker. Even if not required to have a specific calibration, put a sticker on there for at least annual inspection of the operation of the equipment. Keep a file on each piece of equipment, its source, any servicing, calibration or other info.

I've been through both AMRL and CCRL lab audits, in addition to state DOT audits. If they ask for something and you have it at your fingertips, it goes a long way!