|
We know that measurement professionals always try
to push the envelope of accuracy as far as practical and/or possible. It
also seems like everything works against this goal - things like vibration, air
movement, or inherent equipment limitations. We know that any time an
obstacle can be minimized, it can be a significant factor in making positive and
accurate measurements or alignments. That's why we used Invar as the
material for our scale extensions and length standards. Its low
coefficient of thermal expansion (see above) makes
it the perfect material for the job.
To make your job as easy as possible, we designed a flexible system which allows
you to use a variety of standard components to configure a number of different
measuring tools. For example, these tools can be used to construct scale
extensions of various lengths for optical alignment applications. Various
end tips are available to accommodate different types of nominal reference
positions. Or the system can be used to construct known and trusted
distances between targets for the calibration sequences required by laser
trackers, scanners, photogrammetry systems, theodolite systems, etc.
The Three "Cs"
The Brunson Invar System is a simple system of Invar tubing and accessories,
designed with three "Cs" in mind: Connection, Calibration, and Certification.
Connection: All of our Invar system components are designed to be connected together using
standard, removable threaded plugs. Bars of different lengths may be
connected together, yielding any desired length. Various terminators such
as tooling balls or concave tips, as well as scale holders and target holders may
be connected on one or both ends of the bar. The mating surfaces of all
components are machined to tight parallelism tolerances to assure you of a
precision fit.
Calibration: All dimensional components of our Invar system are serialized and
accurately measured - and you're provided with a document specifying the precise length
of each item by serial number.
Certification: All calibrated components are certified as NIST-traceable with included
documentation.
Flexibility
Because our Invar System is so flexible, it is well-suited for several
different applications:
- Precision scale offsets (extensions)
- Three dimensional measurement system scaling (trackers, photogrammetry,
theodolites, etc.)
- Hidden point rods
- Provide known reference lengths for calibration
- Construction of invariant artifacts
We'll customize it for you -
Because the field of precision metrology can be so "quirky", we are
always being asked to construct special items for our customers and clients. We
can create any number of variations on our invar products, including special bar
lengths, custom attachments, tips, fittings, and holders. Bring us any special
requests and we'll do our best to come up with a solution to your problem!
You can browse to our Invar products and accessories using the links below.
|
Everyone knows that almost all materials will expand when the temperature rises, and
shrink when the temperature falls. Often this is not a problem, but
in the measurement world, this effect can cause mischief. Nobody likes to
measure things with a ruler that is capable of expanding and contracting.
It's the same as the old story about the man with two watches - he never knows
what time it really is. So wouldn't it be great to have a measuring device
that was the same length regardless of the temperature?
So what are the numbers? Well, for example, a piece of aluminum which is 5
feet long would change about 0.024 inch in length over a 30 degree Fahrenheit
temperature change. A piece of steel the same length would change about
0.017 inch for the same temperature change. However, compare those numbers
with Invar, which would change in length only 0.001 inch under the same
conditions. It's no wonder that we chose to make our length standards and
scale extension kits out of something so Invariant!