These high quality stage micrometers are used for routine calibration of a
variety of optical measuring instruments, from light microscopes and eye
pieces to x-y stages and optical benches. The stage micrometer is actually
used as a "specimen" in order to calibrate for example, an eye piece reticle.
For the professional light microscope user or researcher, these are the
ultimate calibration standards for their light microscopes.
The single most often asked question is: Are these calibration standards Certified?
The stage micrometers on this page are not traceable to NIST through an
unbroken chain of accredited laboratories, which would be the requirement if
an A2LA or other assessor was asking the question. They are however, being offered
as being traceable to the National Physical Laboratory in the United Kingdom,
which has a Memorandum of Understanding with NIST, by special order. This does seem to
satisfy the demands of most assessors, but that becomes a decision by your
own assessor, not by SPI Supplies or anyone else.
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This means that the stage micrometers are available "traceable"
either with or without a Graticules (e.g. Pyser-SGI) certification.
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So the lowest cost form of the stage micrometer product line is just our own
(e.g. Pyser-SGI) statement that the products have been checked against
traceable standards. The next lowest cost form is the same identical
product but with a Pyser-SGI self-certification document.
Independent Laboratory Certified stage micrometers:
We can now offer the entire range of stage micrometers "certified". The
certification can be done either by the above mentioned National Physical Laboratory in
the United Kingdom or by UKAS
(United Kingdom Accreditation Service) both of which are recognized by NIST in the USA
and other standards making bodies in the rest of the world.
This also means that when the micrometers are purchased "certified", the calibration
is also directly traceable back to the international standard meter held in Paris at the
BIPM (
Bureau international des poids et mesures).
Are all stage micrometers created equal?
Absolutely not! At the risk of sounding like we are making mountains out of
mole hills, we want to make the following "sales pitch" as to why one should
consider spending a bit more for their stage micrometer but at the same time,
getting a far higher quality product and package:
- All SPI Supplies stage micrometers come with an engraved serial
number in the slide mount. If we did not incur the cost of
this special unique engraving, we could sell the stage micrometer for a good
20-25% less. But we decided to not offer such an unmarked product because
all calibration programs, including those based on ISO standards, require
the use of uniquely marked standards. So if you think you are seeing a
"better deal", ask if the slide mount is permanently engraved with a unique
serial number.
- All SPI Supplies stage micrometers come in a stainless steel
mount instead of a much more inherently less expensive aluminum mount. If
you are comparing prices, make sure you are comparing apples to apples and
that you are comparing another stainless steel mount and not aluminum. Most
experienced users of stage micrometers prefer stainless steel for a variety
of reasons, one being the heavier "feel" which makes them easier to handle.
But those who are more economy minded, we can offer a line of
lower cost stage micrometers in aluminum frames.
- All SPI Supplies stage micrometers come in a polished wooden box
with full cushioning in order to provide the highest level protection.
Almost all stage micrometers featuring a lower price come either in a flimsy
(in comparison) plastic box if indeed a box is furnished at all.
- The lines on the SPI stage micrometers have absolutely the
smallest standard deviation in center-of-the-line positioning as well as the
smallest standard deviation of the line width. With some of the lower
priced stage micrometers, it is like comparing night to day, the differences
are so obvious. Unfortunately, it is not all that easy, on a website to
communicate such differences.
- Beware of "all glass" stage micrometers. Why? Well, drop it once
and your expensive stage micrometer is no more. You will instantly
understand why SPI has a philosophy of "no all-glass". Now we are not going
to guarantee that you can not break one of the SPI stage micrometers in a
stainless steel mount, but the SPI micrometers are infinitely more robust
than the all-glass ones and will over time have a much longer useful life time.
So for all of these reasons, we just did not believe we would be fair to our
customers if we were not offering the very finest and most robust stage
micrometers, and when you get right down to it, the difference in quality
between the SPI stage micrometers and those offered at lower prices, very
easily justifies the slightly higher prices.
Selection of the length of the micrometer scale:
The stage micrometers offered by SPI Supplies are offered in lengths ranging
from 0.1 mm all the way up to our newest length of 20 mm, and with
subdivisions as small as 2 µm. So just who would benefit from a longer
rather than smaller scale? For some, it is strictly a matter of
convenience. But for others who might be calibrating a microscope reticle
in the eye piece, having a stage micrometer that has a scale larger than the
one in the eye piece enables one to calculate measurement errors and
therefore, apply a correction factor to compensate. The prices for the 20
mm are slightly higher than the 10 mm versions but for those needing them,
this is a small price incrementally for the value-added.
The stage micrometer is available in two different forms:
Transmitted illumination
For this version, the scale itself is protected by a micro cover glass
exactly to correspond with the specimen it replaces. The majority of
microscopes are corrected for examining specimens through a cover glass
by transmitted light. The calibrated distance depends on the actual product selected, and
can vary from 0.1 mm to 20 mm.
Reflected light illumination
We would recommend this version of the product for anyone using a
metallurgical light microscope. Because most metallurgical samples are
examined without a glass cover slip, this stage micrometer does not have
a cover glass. Hence one also has to use greater care to protect the
surface from accidental damage. The calibrated distance is 1.0mm in length.
Tips for extending useful life time:
Cleanliness is the rule at all times. Keep the stage micrometer free of
dust through the use of
SPI Two-In-One™ OK Easy™ Dusters. And
when not in use in the microscope, it should be always in a protected
(e.g. "clean" environment) and if it has to be set down on a surface, do
not set directly onto a laboratory bench, but put it on a
SPI-Wiper™
lint-free cotton wiper. For effective and damage-free dry cleaning, we recommend using only the
SPI Supplies® Brand
Lens Cleaning Tissues.
Stage Micrometers for Transmitted Light:
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Tuesday February 09, 2010
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