| General - Calibration |
| |
| What
is accreditation and why should I select an accredited laboratory
for my source of calibrations? |
| “Accreditation” is a formal recognition
by an authoritative entity that an organization or individual
is competent to carry out specific tasks. In the field of metrology,
a third party such as NVLAP or A2LA, totally
unaffiliated with the organization in question, ensures the
calibration is being performed correctly
by technically competent individuals. Accreditation translates
to a cost savings in minimizing or eliminating the need for
onsite visits by the customer. If your calibration service provider
is not accredited, you are taking a risk with your quality control
program. Top |
| |
| What
is the difference between NVLAP (the National Voluntary Laboratory
Accreditation Program) and A2LA? |
| The only real difference between these two organizations
is that NVLAP is affiliated with the US National
Institute of Standards and Technology (NIST)
while A2LA resides the private sector, however, both agencies
audit to ISO/IEC IS 17025 (formally ISO Guide
25). Specific criteria that is covered by both organizations
during an assessment include: Top |
· Equipment and environment
·
Methods and procedures
· Validation of uncertainties
· Quality system and reviews
· Record keeping
complaints |
· Measurement
· Traceability
· Organization
· Staffing
|
| |
| What
is UKAS? |
| UKAS is the United Kingdom Accreditation
Service formerly NAMAS. UKAS was formed from the merger of NAMAS
and NACCB in 1995 as a national accreditation body (NAB). It
is part of a network of NABs that assesses technical competencies
of laboratories and grant accreditation to those meeting its
requirements. Top |
| |
| Why
is Troemner Double Accredited? |
| Troemner pursued these accreditations to obtain
the domestic and international recognition that NVLAP
and UKAS carry. By having this double accreditation,
Troemner can provide certification all over the world.
Top |
| |
| General - Terms |
| |
| ISO
Guide 25 (proposed revision: ISO/IEC IS 17025) |
| This guideline sets out the general provisions
which a laboratory must address to carry out specific calibrations
or tests. ISO Guide 25 provides laboratories direction for the
development and implementation of a fundamental quality management
system. Top |
| |
| GLP
Standards |
| Good Laboratory Practices (GLP’s) not only
address the organizational aspects of operation and the conditions
under which laboratory tests are scheduled, conducted, and monitored;
but, also the aspect of recording and reporting test results.
GLP principles are basically used for testing substances and
acquiring data on their properties and/or their harmlessness
to human health and the environment. Top |
| |
| The
National Voluntary Laboratory Accreditation Program (NIST/NVLAP)
|
| Sponsored by the National Institute of Standards
and Technology (NIST), assesses and accredits organizations
based on their technical ability and quality system, following
ISO/IEC IS 17025 (formerly ISO Guide 25).
Top |
| |
| The
National Committee for Clinical Laboratory Standards (NCCLS)
|
| A globally recognized, voluntary consensus, standards-developing
organization that enhances the value of medical testing within
the healthcare community through the development and dissemination
of standards, guidelines, and best practices.
Top |
| |
| The
College of American Pathologists (CAP) |
| An organization that accredits in order to improve
the quality of clinical laboratory services throughout the United
States, through voluntary participation, professional peer review,
education, and compliance with established performance standards.
Top |
| |
| The
Clinical Laboratories Improvement Act (CLIA) |
| A document that outlines minimum
standards for personnel, testing, and quality control for clinical
laboratories. Top |
| |
| Reference
Standard |
| A standard, generally of the highest metrological
quality available at a given location, from which measurements
made at that location are derived. Top |
| |
| Traceability |
| In order to establish traceability, a standard
must have an unbroken and valid relationship to some nationally
or internationally recognized standard. A standard itself can
not really be traceable, but the value assigned to it can as
long as there is an unbroken chain of comparisons all having
stated uncertainties. Top |
| |
| Uncertainty
|
| A measure of the inherent variability of repeated
measurements of a quantity. Uncertainty characterizes the dispersion
of the values that could reasonably be attributed to the measurement.
This parameter is typically reported at a 95% confidence level.
Top |
| |
| Accuracy |
| The closeness of agreement between the nominal
or accepted value and the measured value. Top |
| |
Precision |
| The reproducibility of multiple measurements and
is usually described by the standard deviation, standard error,
or confidence interval. Top |
| |
| Standard
Deviation |
| A statistical measure of the degree of variation
of a set of quantitative data around its mean.
Top |
| |
Weight - Calibration |
| |
|
Why do mass standards take more time calibrate than most laboratory
equipment? |
| For a proper calibration, weights need adequate
time to establish and maintain a thermal equilibrium with the
laboratory before any measurement. One-piece weights take the
longest time to calibrate - adjustments are made on a polishing
wheel that generates heat and requires 4–8 hours to reestablish
thermal equilibrium before any calibration/tolerance checks
on a balance. A quality calibration just can not be performed
in a matter of days and if someone tells you otherwise then
they simply are not following good measurement practices and
the quality of the calibration will be drastically inferior.
In fact, it is our supposition that if this occurs you are not
getting the service that you paid for and you are simply paying
for a calibration sticker. Top |
| |
| I
think my weight may be out of calibration, what should I do? |
| Check for contaminants, scratches, and discolorations.
Be sure to look on the bottom of the weight, since occasionally
matter attaches itself to the bottom and it may go unnoticed.
Top |
| |
| How
can I determine balance error from weight error? |
| The weight error is the measured value correction
plus its associated uncertainty (please refer to a Troemner
NIST/NVLAP Weight Calibration Certificate for an example). You
can use the weight to determine the balance error, but you can
never use the balance to determine the weight error. This means
that if you want to determine the weight error, you must have
a mass standard with a certificate that enumerates the value
correction plus its associated uncertainty or you must have
another certified weight to make a comparison. If you want to
determine the balance error, it is relatively easy if you have
a certified mass standard with the aforementioned data. With
this information you should know how the weight performs plus
or minus its associated uncertainty value. Therefore, the balance
error can be deduced by performing multiple measurements to
see how well the balance executes a measurement. This, of course,
can be recorded and tracked over time, so that a balance uncertainty
can be ascertained as well. Top |
| |
| How
Often Should I have my weights calibrated? Why? Are there any
regulation and/or standard pertaining to calibration intervals?
|
| It is recommended that if you use your weights
infrequently to moderately, you should have them recalibrated
once a year. However, if your weights are used very frequently
or several times a day, then you should have them calibrated
once every six months. Although there are no standards or regulations
that specifically address recalibration intervals, this is the
industry norm in order to ensure that these standards are still
within their specified tolerances. It is
not unusual to see significant “as found” failure
rates on those weights that are not recalibrated on an annual
basis. Top |
| |
| Weight - Terms |
| |
| Austenitic |
| A solid solution in iron of carbon and sometimes
other solutes that occurs as a component of steel under certain
conditions. Austenitic stainless steels usually offer many advantages
such as increased strength, corrosion resistance, lower magnetic
susceptibility, and desirable mechanical and magnetic properties.
Top |
| |
| Calibration |
| The act of determining the mass difference between
a standard of a known mass value and an “unknown”
test weight or set of weights. The process uses a comparison
method and a series of calculations to establish the mass value
and conventional mass value of the “unknown” and
determines a quantitative estimate of the uncertainty
to be assigned to the measurement process as well as the mass
or conventional mass value for the “unknown”.
Top |
| |
| Tolerance
(Adjustment Tolerance or Maximum Permissible Error) |
| The maximum amount by which the conventional mass
of the weight is allowed to deviate from the assigned nominal
value. Top |
| |
| Correction |
| Mass values are traditionally expressed by two
numbers, one being the nominal mass of the weight and the second
being a correction. The mass of the weight is the assigned nominal
value plus the assigned correction. Positive corrections indicate
that the weight embodies more mass than is indicated by the
assigned nominal value. Top |
| |
| International
Prototype Kilogram |
| The platinum-iridium cylinder maintained at the
International Bureau of Weights and Measures (BIPM), at Sevres,
France with an internationally accepted defined mass of 1kg
with zero uncertainty. Top |
| |
| U.S.
National Prototype Standard |
| Platinum-iridium kilogram identified as K20, maintained
at the National Institute of Standards and Technology (NIST),
with a value assigned relative to the International Prototype
Kilogram. Top |
| |
| Nominal
Mass |
| The mass value as marked on a weight.
Top |
| |
| Weight
(Mass Standard) |
| An object representing a specific mass, regulated
in regard to its physical and metrological characteristics:
shape, dimension, material, surface quality, nominal value,
and maximum permissible error. Top |
| |
| Conventional
Mass (Mass in Air) |
| The conventional value of the result of weighing
in air, in accordance to International Recommendation OIML R33.
For a weight taken at 20 degrees C, the conventional mass is
the mass of a reference weight of a density of 8000 kg/m3, which
it balances in air density of 1.2 kg/m3. Top
|
| |
| As
Found Conventional Mass Correction |
| The conventional correction
of the result, as it was received by Troemner, of weighing in
air accordance to International Recommendation R 33. For a weight
taken at 20o C, the conventional mass is the mass of a reference
weight of density 8000 kg·m-3 which it balances in air
density of 1.2 kg·m-3. If the customer requires cleaning
prior to calibration, the after cleaning correction will be
reported. Top |
| |
| As
Left Conventional Mass Correction |
| The conventional correction
of the result, after adjustment repair, or replacement of weighing
in air in accordance to International Recommendation R 33. For
a weight taken at 20o C, the conventional mass is the mass of
a reference weight density 8000 km·m-3 which it balances
in air density of 1.2 km·m-3. The As Found will equal
the As Left Conventional Mass Correction if the mass(es) did
not require adjustment, repair or replacement.
Top |
| |
| Air
Buoyancy |
| Air buoyancy is a net upward force due to atmospheric
pressure. In a gravimetric analysis, you must have an air buoyancy
correction to get to the true mass. Top |
| |
| Mass
in a Vacuum (True Mass) |
| The mass of a weight as if it were measured in
a vacuum. Top |
| |
| As
Found Mass in a Vacuum |
| The measured value of the mass(es) as they were
received by Troemner. If the customer requires a cleaning prior
to calibration, the after cleaning value would be reported.
Top |
| |
| As
Left Mass in a Vacuum |
| The measured value of the mass(es) after they
were adjusted, repaired or replaced when necessary. The As Found
Mass in a Vacuum will equal the As Left Mass in a Vacuum if
the mass(es) did not require adjustment, repair or replacement.
Top |
| |
|
Reference Standard |
| A standard, generally of the highest metrological quality available at a given location, from which measurements made at that location are derived.
Top |
| |
|
Traceability |
| Property of the result of a measurement or the value of a standard whereby it can be related to stated references, usually national or international standards, through an unbroken chain of comparisons all having stated uncertainties. In other words, in order to establish traceability there must be an unbroken and valid relationship to some nationally or internationally recognized standard. A standard itself can not really be traceable, but the value assigned to it can.
Top |
| |
|
Uncertainty |
| Parameter associated with the result of a measurement that characterizes the dispersion of the values that could reasonably be attributed to the measurement. This is the range of values within which the true value is estimated to lie. In other words, the uncertainty is a measure of how confident you are in the accuracy of the results resulting from a measurement.
Top |
| |
| Pipette - Calibration |
| |
| What
is a pipette? |
| A pipette is a hand held measuring instrument
designed to deliver a pre-determined volume of liquid from one
vessel to another. Top |
| |
| My
pipette leaks and can you assist me with a solution? |
Pipettes can leak for the following reasons:
a) The tip is incorrectly attached
b) There is a foreign object (i.e. dirt, grit, etc) between
the piston, o-ring, and nose cone.
c) The o-ring has been damaged or warped
Solutions to the aforementioned problems:
a) Securely attach the tip to the nose cone
b) Clean and grease tip cone module and o-ring; attach new
tip.
c) Change the o-ring Top
|
| |
| I
just had my pipette calibrated but it seems to be dispensing
inaccurately. What can I do to resolve this problem? |
- Check to see if the tips are securely attached
- Was the pipette dropped, or has the pipette been subject
to over-winding / under-winding the micrometer?
- Was the operator using good techniques? Based on our experience,
as many as 25% of all pipetting errors are directly related
to the operator. Top
|
| |
| How
many times a year should a pipette be calibrated? |
| It depends on the number of times the pipette
is used and the quality standards of the laboratory. ASTM E:
1154-89 11.23 recommends that pipettes receive an evaluation
at least on a quarterly basis. Top |
| |
| Can
my pipette be autoclaved? |
| Some pipettes can be autoclaved
while others can not. It is best to check with the manufacturer
if there is ever any doubt. Top |
| |
| What
are the common methods of pipette calibration? |
1. Gravimetric: requires a controlled
environment, a high precision balance,
a skilled pipette technician and the use of statistics. Principle:
given a certain mass of water with a known specific gravity,
its volume can then be calculated. The gravimetric method
of calibration entails weighing deonized (i.e. distilled)
water on a balance and converting from a mass unit to a volumetric
unit by utilizing the Z-factor. (Z-factor
converts from a mass unit to a volumetric unit and includes
calculations for air buoyancy, temperature, humidity, barometric
pressure and the cubic expansion coefficient).
2.Colorimetric or Photometric involves the analysis
of volumes of diluted dye in a cell of a known path length.
If a beam of monochromatic light passes through homogeneous
solutions of equal path-lengths, the absorbance measured is
proportional to the dye concentration. Principle: An unknown
volume of dye can be pipetted into a known volume of diluent,
the resulting dye concentration can be measured photometrically
and the volume can be calculated. This method employs the
use of a spectrophotometer and reagent dyes. As more and more
of the dye is dispensed, the greater the amount of energy
that is being absorbed and if course, the less that is being
detected. The instrument uses the information to calculate
the volume. Top |
| |
| Pipette - Terms |
| |
| Glass
Pipettes |
 |
volumetric
pieces of glass calibrated to deliver a specific volume
of liquid. Glass pipettes cannot be “calibrated”
in the true sense of the word since the graduations
cannot be adjusted. The glass pipette can be tested
and “verified”. Top |
|
| |
| Air
Displacement Pipettes |
 |
Pipettes
that have a piston in a cylinder or capillary tube that
moves to the appropriate position once the volume is
set. The key feature of an air displacement pipette
is the fact that a specified volume of air always remains
between the piston and the liquid. Top |
|
| |
| Positive
Displacement Pipettes |
 |
Pipettes that also have a piston in a cylinder
or capillary tube that moves to the appropriate position
once the volume is set, however, this type of pipette
always has the piston in direct contact with the liquid.
Top |
|
| |
| Autoclaving |
| The act of placing an instrument inside
a machine specifically designed to sterilize an instrument by
reaching very high temperature and pressures.
Top |
| |
| Air
Buoyancy |
| Air buoyancy is a net upward force
due to higher pressures at lower altitudes. Since in a gravimetric
analysis, you are essentially converting the “weight”
of a liquid to a volume, you must have an air buoyancy correction
to get to the true mass. Top |
| |
| Dead
Volume |
| The part of the total liquid volume
that is held in the operational part of the device and not delivered.
Top |
| |
| Dilutor |
| A measuring instrument designed to
take up different liquids and deliver them in combination so
that they comprise a predetermined ratio, a predetermined volume,
or both. The reservoir of diluent may be integrated with the
instrument or connected externally. Top |
| |
| Dispenser |
| A measuring device designed to deliver
predetermined volumes of liquid from a reservoir. The reservoir
may be integrated with the instrument or connected externally.
Top |
| |
| Expansion
Factor |
| The quantification of expansion due
to thermal conductance.
K = 1-µ (T-20)
Where:
K = Expansion Factor
µ = Cubic expansion coefficient
T = Temperature, degrees Centigrade Top |
| |
| Isothermal
Condition |
| This means that the pipette and the
environmental temperature are equal. This is accomplished by
allowing the pipette to equilibrate to the temperature of the
laboratory for a certain period of time. Top |
| |
| Nominal
Volume |
| The stated volume for which performance
is specified. Top |
| |
| POVA |
| A piston or plunger operated volumetric
apparatus. Top |
| |
| Pre-rinsing/Pre-wetting |
| The action of pre-coating the inside
of the liquid contacting parts with a thin film of the same
liquid to be pipetted. Top |
| |
| Z-factor |
| Z-factor converts from a mass unit
to a volumetric unit and includes calculations for air buoyancy,
temperature, humidity, barometric pressure and the cubic expansion
coefficient. Top |
| |
| Trade-in Promotion |
| |
| How do I get pricing for the weights and weight sets included in this promotion? |
| Pricing by part number is available online. Please click here to download a PDF file of the price list. Top |
| |
| What weights are included in the promotion? |
| Troemner Alloy 8 Stainless Steel Ultra Class and Class 1 two piece individual weights and weight sets. Capacities range from 1 g to 50 kg. Top |
| |
| Are Weight Calibration Certificates included in the promotion? |
| You can include a Traceable, NVLAP or UKAS weight calibration certificate with your order. You will receive 40% off the certificate when included with an Alloy 8 Stainless Steel Ultra Class or Class 1, 2 - 200g x 1 mg two piece weight set. You will receive 30% off the certificate when included with an Alloy 8 Stainless Steel Ultra Class or Class 1 two piece individual weight or weight set. Top |
| |
| What is the lead time for my new weights? |
| The lead time is based on when your trade-in weight(s) and completed order forms are received at Troemner. Top |
| |
| What if I am interested in purchasing a non-standard weight set? |
| Non-standard weight sets are included as part of this promotion. For pricing, please refer to the pricing for each individual weight that will be included in the weight set. If you would like a weight case for the non-standard weight set, please contact a Troemner sales representative at (888) 247-2175 for a quotation. Top |
| |
| Are weight cases included with the weights and weight sets included in this promotion? |
| Weight cases are included with all the weight sets and Ultra Class two piece individual weights 200 g and higher. Top |
| |
| If a weight case is not included with my new weights, how do I receive a replacement weight case? |
| If you need a weight case for your new weights, indicate on your order form that you would like a Troemner sales representative to contact you with pricing for a replacement weight case or contact a sales representative directly at (888) 247-2175. Top |
| |
| What weights and weight sets do not include weight cases? |
| Weight cases are not included with Class 1 two piece individual weights, Ultra Class two piece weights less than 200 g and any non-standard weight sets. Top |
| |
| Do Troemner weights fit in other manufacturer's weight cases? |
| No, Troemner's weights do not fit other manufacturer's weight cases. We manufacture weight cases specifically designed for all our weights. Top |
| |
| What happens if I forget to include the order forms with my trade-in weights? |
| It is very important that your order forms are included with your weights. If the forms are not included, your weights will be sent to the Mass Calibration Laboratory for recalibration and your account charged accordingly. Top |
| |
| Where do I send my trade-in weights? |
| Please ship your trade-in weight(s) to Henry Troemner, LLC, 201 Wolf Drive, Thorofare, NJ 08086 Attn: Trade-in Promotion. Click here to download the shipping label and order forms that must be included with your trade-in. Top |
| |
| Who will be responsible for the cost to ship my trade-in weights to Troemner? |
| You are responsible for the cost to ship your trade-in weights to Troemner. You can choose any shipping method. Top |
| |
| How should I ship my trade-in weights? |
| You can choose any shipping carrier for sending your trade-in weights to Troemner. It is very important that you include the shipping label we provide on the outside of the shipping box. You are not required to ship the weights in a special packaging or a protective manner. If your weights are shipped in a weight case, the case will not be returned. Top |
