OHAUS Innovation in Calibration
Mass measurement is one of the most frequently performed
tasks in a laboratory environment. Users commonly weigh a variety
of materials several times a day, and the speed and accuracy of
balances are paramount in the lab.
Today's labs have the goal of increasing speed,
efficiency and accuracy all while maintaining costs at
reasonable levels.
You spent all afternoon on that test run, only to find out later
that your balance was out of calibration... Now you'll need to
scrap all the data based on the testing you have completed, and
start from the beginning - a waste of time and money. With mounting
pressure today on efficiency and reducing costs, a balance that is
out of calibration can be costly in many ways for a
laboratory. While it is safe to say that measurement accuracy
is more vital then ever, why are laboratory balances often out of
calibration?
It's because of the tedious, manual and outdated process required
to calibrate a balance - which is contradictory to the movement
towards technologically advanced and automated laboratory
instruments. With the goal of increasing speed, efficiency and
accuracy in mind, a focus has been placed on improving the balance
calibration process.
Traditional Balance Calibration
The traditional method of calibrating electronic balances is with
an external calibration mass. Users will typically calibrate with a
"span calibration" method, beginning with no weight on the pan to
obtain the zero point, then placing a mass on the balance to
achieve a span point (usually at maximum scale capacity). The
process from start to finish is time consuming, and has the
following limitations that contribute to users not calibrating
balances correctly-
| Physical Limitations |
Technical Limitations |
- Laboratory must purchase a calibration mass that is within the
tolerance limits of the balance, which is often very costly
relative to the price of the instrument.
- High precision calibration masses are very sensitive to abuse;
even touching them with a bare hand can affect their accuracy over
time.
- External masses can be lost or misplaced easily, especially in
a busy lab.
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- Calibration is only valid for a given temperature range. As
temperature changes in the weighing environment, the calibration of
the instrument is affected resulting in less accurate weighing
results.
- In order to ensure accurate results again, the user must
recalibrate their balance.
- Using only two calibration points can make the balance
susceptible to a non linear response through the weighing
range.
|
Calibration Innovation
Since the 1990's, OHAUS Corporation has been developing and
providing balances and scales with internal calibration technology,
addressing the many shortcomings of external masses. OHAUS has
currently developed three levels of internal calibration systems,
each geared to specific user requirements. Each one of the internal
calibration concepts adhere to the following fundamentals-
- All calibration methods are based upon real masses, which
reside inside the balance or scale, and will never be damaged or
lost.
- All calibration methods have a system to adjust the internal
mass value to match that of an external certified mass if so
desired (CalAdjust).
- All internal calibration systems offered are fast, friendly and
the calibration results can be documented.
In order to compensate for the physical and technical limitations
of traditional balance calibration, a variety of internal
calibrations are put to use by OHAUS. These three internal methods
of calibration, entitled InCalTM, AutoCalTM, and Dual Mass
AutoCalTM, are offered by OHAUS in hopes of bringing an innovative
and productive level of technology to the calibration
problem.
InCalTM , a basic level of internal calibration, allows the scale
to calibrate itself with one mass located inside the balance, at
the push of a button. In response to the physical limitations of
previous calibration techniques, InCalTM allows for fast, easy
calibration, without worrying about purchasing, locating and
storing an external mass. The balance will only calibrate when
instructed by the end user. In addition, this method of calibration
is ideal for labs on a budget, who need the benefit of internal
calibration at the lowest cost possible.
AutoCalTM is the next level of internal calibration, technology
that allows automatic internal calibration. As the name suggests,
the balance will automatically calibrate itself (performed with a
single internal mass) when it senses a change in the environment
large enough to affect weighing results. With AutoCal, even if the
operator is away for hours at a time, the balance will always be
calibrated upon return - without any work for the end user. AutoCal
works well in laboratories that are busier and don't have extra
time to calibrate their balance before every use- the balance is
always ready to weigh.
Dual Mass AutoCalTM is the most advanced level of internal
calibration offered by OHAUS. Dual mass AutoCal is similar to
AutoCal with the exception that the instrument has two internal
calibration masses that allow the balance to perform three-point
linear calibrations (zero point, midpoint, max point), instead of
the typical two-point span calibrations. Three point calibrations
are more desirable than two point span calibrations because they
result in more linear results throughout the weighing range - for
ultimate in accuracy. The time and temperature features of standard
AutoCal are included in Dual Mass Auto Cal. This system is ideal
for labs who require the absolute finest weighing precision
available, but who do not have the time to repeatedly calibrate
analytical and semi-micro balances.
More on Cal Adjust
Calibration Adjust may be used to adjust the results of the
internal calibration. An adjustment can be made to the balance
calibration value when there is a difference between the nominal
value of an external mass and the actual displayed reading. This
feature allows the user to fine-tune the internal calibration
system to provide the same results when compared to the external
mass to ensure highest accuracy and to also provide another method
of traceability.
Summary
Calibrated lab instrumentation is vital in today's research
environment, and while most technicians are aware of the
importance, the traditional process of calibrating a laboratory
balance has many limitations hindering their accuracy. The solution
to problems associated with external mass calibration can be found
within automated solutions, such as the ones available and outlined
by OHAUS. Automated calibration solutions are tailored resolutions
for laboratories seeking a better, more physically and technically
function method of calibration.