U.S. patent application number 13/644304 was filed with the patent office on 2013-01-31 for check weight, method and system to ensure traceability of same.
This patent application is currently assigned to METTLER-TOLEDO AG. The applicant listed for this patent is METTLER-TOLEDO AG. Invention is credited to Hans Joerg Burkhard, Michael Greuter, Holger Haussmann, Roland Nater, Patrick Von Arx.
Application Number | 20130025344 13/644304 |
Document ID | / |
Family ID | 38670555 |
Filed Date | 2013-01-31 |
United States Patent
Application |
20130025344 |
Kind Code |
A1 |
Haussmann; Holger ; et
al. |
January 31, 2013 |
CHECK WEIGHT, METHOD AND SYSTEM TO ENSURE TRACEABILITY OF SAME
Abstract
A check weight (1) that is used to check a gravimetric measuring
instrument, specifically a balance, or to check a further weight,
is provided with a means of identification. This marking which is
applied on the outside surface of the check weight includes a
permanently affixed machine-readable identification code (2) which
makes the specific weight piece individually recognizable. This
opens the possibility for a method whereby an individually
identifiable check weight can be traced back in time. A system for
tracing check weights back in time includes one or more reader
devices (6) that serve to record the marking, one or more
processors (10) wherein the machine-readable identification code
can be converted back into an identification code that can be
electronically processed, and one or more data storage units, in
particular a database (8) serving to store at least the data
contained in the identification code.
Inventors: |
Haussmann; Holger; (Jona,
CH) ; Nater; Roland; (Winterthur, CH) ; Von
Arx; Patrick; (Winterthur, CH) ; Burkhard; Hans
Joerg; (Wolfhausen, CH) ; Greuter; Michael;
(Dietlikon, CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
METTLER-TOLEDO AG; |
Greifensee |
|
CH |
|
|
Assignee: |
METTLER-TOLEDO AG
Greifensee
CH
|
Family ID: |
38670555 |
Appl. No.: |
13/644304 |
Filed: |
October 4, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12648815 |
Dec 29, 2009 |
8281640 |
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13644304 |
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PCT/EP2008/058650 |
Jul 4, 2008 |
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12648815 |
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Current U.S.
Class: |
73/1.13 |
Current CPC
Class: |
G01G 21/26 20130101 |
Class at
Publication: |
73/1.13 |
International
Class: |
G01G 23/01 20060101
G01G023/01 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 6, 2007 |
EP |
07111973.9 |
Claims
1. A check weight for a gravimetric measuring instrument, in
particular for a balance, comprising: a weight piece; and an
identification code, permanently affixed to an outside surface of
the weight piece, the identification code providing a unique
machine-readable identity to the weight piece individually
recognizable.
2. The check weight of claim 1, wherein: the identification code is
implemented in a binary form of representation.
3. The check weight of claim 1, wherein: the identification code is
configured as a matrix code.
4. The check weight of claim 1, wherein: the identification code is
configured as a miniaturized barcode.
5. The check weight of claim 1, further comprising: a weight
number, incorporated into the identification code.
6. The check weight of claim 5, further comprising: additional
information about the weight piece, incorporated into the
identification code, comprising at least one of: a production lot
number; a production date; a date on which the identification code
was applied; and a date of the original calibration.
7. The check weight of claim 1, wherein: the check weight consists
of a metal alloy with an invariant material density.
8. A check weight of traceable history, comprising: a weight piece;
a set of certificate data, stored in an electronic manner on a
storage device external of the weight piece, the certificate data
set comprising: a unique identification code; a set of initial
calibration data; and at least one set of recalibration data; a
marking formed in the weight piece, such that reading the marking
with a processor in communication with the storage device generates
a signal to the storage device that associates the weight piece to
the set of certificate data.
9. The check weight of claim 8, wherein: the check weight consists
of a metal alloy with an invariant material density.
10. The check weight of claim 9, wherein: the marking is formed in
a surface of the weight piece.
11. The check weight of claim 8, wherein: the marking is formed in
a surface of the weight piece.
12. The check weight of claim 10, wherein: the marking is a matrix
code.
13. The check weight of claim 11, wherein: the marking is a matrix
code.
14. The check weight of claim 12, wherein: the marking is formed by
a metal removing method.
15. The check weight of claim 13, wherein: the marking is formed by
a metal removing method.
16. The check weight of claim 8, wherein: the processor and the
storage device are each associated with a balance.
17. The check weight of claim 8, wherein: the marking is
implemented in a binary form of representation.
18. The check weight of claim 8, wherein: the certificate data set
further comprises at least one of: a production lot number; a
production date; a date on which the marking was applied; and a
date of the original calibration.
19. The check weight of claim 8, wherein: each set of recalibration
data comprises at least one of: a recalibration identification
number; a recalibration data; an identity of the person performing
the recalibration; conditions under which the recalibration took
place; the weight value at the time of recalibration; statistical
data concerning the recalibration.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. Ser. No.
12/648,815, filed on 29 Dec. 2009, now U.S. Pat. No. 8,281,640,
issued on 9 Oct. 2012, which is a continuation under 35 USC
.sctn.120 of PCT/EP2008/058650, filed on 4 Jul. 2008, which is in
turn entitled to benefit of a right of priority under 35 USC
.sctn.119 from European patent application 07 11 1973.9, which was
filed 6 Jul. 2007. The content of each of the applications is
incorporated by reference as if fully recited herein.
TECHNICAL FIELD
[0002] The disclosed embodiments, which are in the field of
metrology, relate to weights that are used to check balances and to
check or measure other weights.
BACKGROUND
[0003] Highly sensitive balances in particular, such as
microbalances and ultra-microbalances, analytical balances or
precision balances, are subject to influence factors which can lead
to measurement deviations over the course of time. Such balances
therefore have to be checked on a regular basis in order to ensure
that they produce accurate weighing results. Such checks, so-called
routine tests which are performed within a regulatory framework,
are officially required in particular for balances used in the
fields of pharmacology, biotechnology and food technology and are
set down in FDA regulations (Food and Drug Administration, U.S.
Department of Health and Human Services). However, the
manufacturers of balances also recommend to their customers that
balances used in commercial applications be checked at regular
intervals.
[0004] To determine deviations one uses check weights with defined
nominal values. According to norm standards, for example the
internationally recognized recommendation R111 published by OIML
(Organisation Internationale de Metrologie Legale), these kinds of
check weights are subject to tolerance limits within which the
actual weight values have to lie in relation to the nominal weight
value. Under this tolerance system, the weights are divided into
different weight classes according to different precision
requirements. For example, the tolerance limit for a one-milligram
weight in class E1 (the highest accuracy class) is .+-.0.003 mg,
while the tolerance limit in class M1 (the lowest accuracy class
applicable to a one-milligram weight) is .+-.0.2 mg.
[0005] Check weights, as the term is used in the present context,
should be understood to include weights of all kinds that are used
to check and/or calibrate and/or certify balances or weights
particularly in areas that are subject to regulatory control. These
check weights are occasionally also called verification weights or
calibration weights.
[0006] Check weights can be made of one solid piece or of several
pieces of material. Single-piece check weights are made of one
block of material, while check weights composed of more pieces have
a cavity on the inside which is filled with so-called adjustment
material up to the point where the nominal weight has been
attained, whereupon the cavity is closed off. It should be noted,
however, that check weights made up of a plurality of pieces are
not permitted in the highest accuracy classes according to
OIML.
[0007] As the actual weight values of check weights will change
over time due to wear, this could have the consequence--in cases
where these check weights are used to check balances--that weighing
results or industrial processes may also run outside their
tolerance limits. One must therefore make certain that in any given
case the check weight tolerance is being met. To accomplish this
purpose, the check weights themselves are regularly checked against
other check weights, so-called verification standards. The time
intervals for such verification checks are dependent on the
respective accuracy class of the weights or on the area of
application and the particular circumstances of the
application.
[0008] For each individual check weight, a certificate is issued on
request, which states the actual weight value at the specific time,
the nominal weight value, the accuracy class relative to a given
class limit, as well as a calibration I.D. number and the number of
the calibration certificate. Each time another verification check,
a so-called recalibration, is performed at a later date, a new
certificate is issued in which a new certificate number is assigned
to the same weight, but the same calibration I.D. number remains
assigned to the weight.
[0009] The check weights or sets of check weights with different
weight values are stored in special weight container cases for the
distribution and later, at their place of application, for storage
by the user. In such a container case, there are appropriately
dimensioned seating recesses provided for each weight denomination,
so that for example a 100-gram weight can be set with a precise fit
only into the recess for 100-gram weights, but not into a recess
for a 50-gram weight, while it would not completely fill out the
recess for a 200-gram weight, so that a correlation between weights
and recesses is possible based on size. The certificates of the
individual weight pieces are placed into these container cases so
that in principle the connection between certificate and check
weight is established. This is normally made evident by means of a
label that is affixed to the container case, on which the
calibration I.D. number is printed, and a further label on which
the certificate number is printed.
[0010] Due to the manual handling of the check weights in the
process of performing the aforementioned routine tests, it is
however easily possible that the connection between the weight
piece and its associated certificate and/or its calibration I.D.
number gets lost. This can happen for example if a balance is to be
certified or calibrated for 400 grams and if for this
purpose--because there is no 400-gram weight available--a 200-gram
weight piece and two 100-gram weight pieces are used instead.
Regardless of whether the two 100-gram weight pieces are stored in
the same container case or come from two different container cases,
it is possible that handling errors will occur in the process,
resulting in a mix-up of the two 100-gram pieces. The consequence
of this is a wrong match between certificate and weight piece,
which cannot even be effectively checked, so that an error of this
kind remains undiscovered.
[0011] This method has the problem that there is no definite
correlation that ties the certificate to the check weight, i.e. to
the physical weight piece itself. The handling of such check
weights therefore requires the utmost diligence in order to ensure
that the correct match between certificate and calibrated weight
piece is permanently preserved. Still, there is no guarantee of
achieving this goal. Inadvertent mix-ups cannot be ruled out, nor
can they be reliably detected after the fact.
[0012] In German laid-open application DE 40 06 375 A1, the concept
of equipping check weights with a code marking that represents the
weight value is disclosed. This is realized by electronically
storing the weight value in an electronic circuit which is
contained in the weight piece itself. This has the disadvantage
that electrical contacts are necessary for the transmission of the
data from the weight piece to the balance and vice versa and that
because of these contacts, the weight has to be set in a defined
position and, in particular, special devices are required which
make the manufacture and use an error-prone process. Also, an
electronic data storage is not totally error-resistant, so that
data errors due to inappropriate handling of the check weights or
also due to material fatigue, and thus calibration errors which
occur as a result, cannot be completely ruled out in this case
either. Furthermore, check weights of this kind are expensive to
produce.
[0013] Since the identification marking only contains the initial
actual value, this coding system does not provide an individual
identification of each weight piece, but only a classification
according to weight value. Under the method described in this
reference, an individual weight piece can be traced back only
insofar as the highest possible number of weight checks that can be
performed is entered in the electronic data storage device of the
weight and each weight check is counted until this upper limit is
reached. Traceability beyond this time frame or in regard to other
attributes such as place and date of manufacture, production lot
number, etc., is impossible. A recall campaign which could be
necessary for example in case of a manufacturing error in a
production lot is therefore not possible for check weights that are
identified in this way.
[0014] It is therefore an objective to advance the design of a
check weight in such a way that the weight is permanently and
individually traceable.
SUMMARY
[0015] This objective is met through the concept that the check
weight itself carries an identification, specifically a marking by
way of a machine-readable identification code on the outside of the
weight, whereby each weight piece is made individually
recognizable.
[0016] This concept has the advantage that the check weights can be
permanently and reliably matched to their certificates and that all
data can be read and processed by a machine and also be centrally
stored if required. Mix-ups in the handling of the weights can thus
to a large extent be either avoided or reliably detected after they
have occurred. Furthermore, for example if check weights that have
been graded as OIML Class E weights are found to be out of
tolerance, such weights can be reassigned to a lower accuracy class
without any problem.
[0017] Such a system of identification is advantageous for check
weights of monolithic construction as well as those assembled from
more than one piece. Check weights are made of a metal or a metal
alloy of an invariant material density that is prescribed by the
applicable norm standards.
[0018] Placing the identification code on the outside of the weight
piece has the advantage that the processes of affixing the code and
of reading it can be realized in a simple manner.
[0019] In advantageous embodiments it is intended to implement the
identification code in a binary form of representation, in
particular as a data matrix code or as a miniaturized barcode.
[0020] In preferred embodiments, the identification code includes a
weight number that is uniquely assigned to the weight piece.
[0021] In practical further developed embodiments, the
identification code contains further data about the respective
weight piece, including for example the production lot number and
specific dates, in particular the production date, the date when
the marking was applied and/or the date of the original
calibration. This has the advantage that during weight checking
processes the data of the check weight can also be obtained without
accessing external databases or data backup on in-house storage
media and such processes are therefore simplified and
expedited.
[0022] A further objective is to provide a method through which
check weights of the foregoing description can be traced back in
time. This is achieved by: [0023] 1) establishing an identification
code, [0024] 2) converting the identification code into a
machine-readable code format, and [0025] 3) placing the code in the
machine-readable format as a marking or a distinguishing means on
the weight piece.
[0026] The identification code contains essentially a weight number
that is uniquely assigned to the check weight. However, it is also
conceivable to set up the identification code in any other way that
may be desired. The only essential requirement is that the
identification code thus established has to be suitable for
conversion into the intended machine-readable code that is to be
put as a marking on the weight piece. This process can be carried
out immediately following the production of the check weights or
also at a later point in time. Including the marking within the
scope of the production process has the advantage that every single
weight piece is identifiable and thus traceable already at the
completion of the production process. Applying the marking at a
later time on the other hand has the advantage that check weights
that are already in use, in particular if the correlation with
their respective certificate has been lost, can afterwards be given
an identification which makes them traceable again.
[0027] It is intended to implement the code conversion in practice
by converting the identification code into a matrix code or a
miniature barcode.
[0028] In an advantageous implementation of the marking method
using a binary form of representation, the marking process is
performed with a laser. This has the advantage that the marking
process can be performed without loss of material or at worst an
only minimal loss and that the mark is at the same time connected
in a permanent way to the weight piece. Known laser marking
processes can produce an identification code pattern by means of a
matte finish or through the method of the so-called annealing
colors.
[0029] Other inscribing methods that are well suited for the
application of a marking include for example pin marking, etching,
or electron beam scribing. But further methods, other than those
mentioned here, are likewise conceivable.
[0030] According to an advantageous further development of the
method, after the marking has been applied to the check weight, the
respective identification code is permanently stored in a database.
This creates the advantageous possibility to systematically process
and administrate the registered identification codes and the data
of the weight pieces marked with them. It is advantageous to also
register and store the certificate data in the database together
with the identification code. Thus, the certificate data for
individual single check weights can automatically be kept available
and sent out on request in a simple and reliable manner.
[0031] When a certificate is made out for a control weight, it
contains a unique reference to the identification code.
Particularly if the identification code includes a weight number
that is uniquely assigned to the weight, the weight number is also
stated on the certificate.
[0032] As a checking-, calibrating- or recalibrating procedure can
also include a comparison of a further check weight against a first
check weight, in particular against a verification standard, it is
advantageous if the identification code of the first check weight,
specifically of the verification standard, is likewise recorded in
the database, and it may also be stated on the certificate. In this
way, a high degree of traceability can be achieved.
[0033] The certificate data further include the calibration I.D.
number, the certificate number, the issue date of the certificate,
the shape and material of the check weight, the identity of the
person performing the weight check, the conditions under which the
weighing took place, the environmental conditions such as
temperature and barometric pressure, the current weight value, as
well as statistical data concerning the weight check.
[0034] As the weight pieces are recalibrated from time to time, it
is a preferred practice to establish a history file for the
specific weight based on the chronological sequence of certificate
data. With the history file, measured and/or stored data can be
compared to those of a preceding certificate, the results can be
processed further and, if desired, the results can be used to
predict the extent to which the weights remain usable in the
future.
[0035] When a routine test is performed, i.e. to check a balance by
means of a check weight, a program can be executed in the processor
of the balance whereby the identity of the check weight is
investigated and validated before the weighing test is started.
[0036] A further objective is to provide a system whereby check
weights can be traced individually on a permanent basis. The
described embodiments have the advantage that all of the
individually marked weight pieces can be systematically
administrated and kept in particular under a centralized control,
and that all of the data belonging to a given individual weight
piece can be accessed at any time. The one or more processors can
convert the marking code back into the underlying identification
code and directly make use of the latter. The at least one memory
unit serves to save the identification code and, advantageously,
also further registered data (including for example the certificate
data) belonging to the respective weight piece in a permanent and
retrievable kind of storage. Such data are ideally kept available
in a database which provides a centralized access and rapid
systematic processing capability. With this, the basis of the
traceability of a given weight is established, which over the life
of the check weight will for example allow a retroactive assessment
of past wear and thereby also allow extrapolations for the future.
This can for example include a recommendation to change the
recalibration interval or also to assign a weight to a lower class
if it has been found to exceed its applicable tolerance. Thus the
highest possible quality in the surveillance of check weights is
assured, which increases the reliability of the balances and/or
weights that are verified with these check weights.
[0037] According to a further advantageous embodiment of the
system, the at least one processor is equipped with the capability
to send out reports based on the results and/or extrapolations
generated, such as for example a notice regarding the expiration of
a verification time interval. This has the advantage that the
surveillance of the check weights and the measurements performed
with them can be systematically and reliably controlled from a
central place, for example by the manufacturer of the weights. Thus
there is assurance that the user of the check weights are alerted
directly and reliably about any actions that need to be taken,
which increases the quality of the respective measurement
systems.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] In the following, the disclosed embodiments are explained in
more detail with references to the drawings, wherein:
[0039] FIG. 1 depicts an example of a check weight in side
view;
[0040] FIG. 2 depicts a top view of the FIG. 1 check weight,
wherein the machine-readable identification code in the form of a
marking is indicated schematically;
[0041] FIG. 3 shows a magnified image of a matrix-type marking that
is put on a weight;
[0042] FIG. 4 schematically depicts a system for the traceability
of a check weight; and
[0043] FIG. 5 is a flowchart diagram showing the time sequence of a
routine test.
DETAILED DESCRIPTION OF THE DRAWINGS
[0044] FIG. 1 shows an example of a check weight 1. Of course, the
proportions of such check weights 1 can vary, or the weights 1 can
have a completely different shape depending in particular on the
nominal weight value. For example the weights with the smallest
nominal values are normally configured as so-called wire weights or
sheet metal weights.
[0045] FIG. 2 illustrates a check weight 1 of the same type as in
FIG. 1, with a marking in the form of a matrix code 2 that contains
an identification code. The shape and size of the matrix code 2 are
not true to scale. Depending on the kind of marking being used, the
shape and size of the marking can vary. However, in the case of the
more accurate weight classes E and F, the maximum size is
prescribed by the norm standard. The way in which the marking is
arranged on the weight piece can likewise vary. Advantageously, the
marking is placed on top in order to be easily readable. However,
it is just as conceivable to put the marking at some other location
such as laterally or on the underside.
[0046] FIG. 3 shows an example for the design of such a marking 2
in the form of a matrix. As an example, the illustrated matrix 2 is
a twelve-by-twelve array of matrix cells 3, 3', wherein the two
binary values are represented in this case, respectively, by black
matrix cells 3 and white matrix cells 3'. The border rows of cells
4 and 4' meeting at one corner of the matrix and the border rows 5
and 5' meeting at the opposite corner each form a pattern which
allows the reader device to find the matrix code and to read and
interpret it in the correct orientation. The border rows of cells
with uniform binary values (black) running in the directions of the
arrows 4, 4' represent the so-called finder pattern, while the two
border rows of cells with alternating values running in the
directions of the arrows 5, 5' along the respectively opposite
borders of the matrix represent the so-called orientation pattern.
The finder pattern 4, 4' is used to find the matrix code on the
weight, while the orientation pattern 5, 5' along the respectively
opposite borders serves for the correct orientation in the reading
and evaluating of the code. The cells enclosed by the two border
patterns 4, 4' and 5, 5' represent the actual identification
code.
[0047] The representation of the binary light and dark bits can be
realized in the manufacturing process for example by applying a
matte finish to an originally polished surface for the matrix cells
3 shown in black in the drawing. Other techniques of producing
binary representations can also be used. One example is a set of
indentations produced for example through the pin-marking process,
or a color change achieved by surface annealing with a laser, or
alternatively by etching.
[0048] FIG. 4 represents a schematic overview of a system to
establish the traceability of a check weight 1 as described herein.
The reader device 6 which is equipped with processor 10 reads the
marking on the weight, in this case the matrix code 2. The
processor 10 converts the matrix code into an identification code
and transmits the latter to a computer 7 which is likewise equipped
with one or more processors. The computer 7 is connected to a
database 8 which contains all of the data needed to issue a
certificate 9. Based on the identification code, the computer 7 is
now enabled to retrieve the required data from the database 8 and
to issue a certificate 9.
[0049] To ensure that every identification code is issued only
once, the inscribing device (not shown here) which generates the
marking, i.e. the matrix code 2, and which includes for example a
laser, is equipped with appropriate software modules.
[0050] The database 8 has the capability to accept further data
associated with the stored identification code, in particular data
that are required for the certification, but also data that are
generated only at later time, for example in connection with
recalibrations of the check weight.
[0051] There can further be means which allow error checking of the
matrix code 2 that has been read into the system.
[0052] By way of the data connection 12 which is only symbolically
indicated, data can be transmitted from the processor 11 of the
computer 7 to other processors and/or computers (not shown in the
drawing) or received by the latter. These processors can be in
direct connection with the processor 11, or they can also be part
of an intranet or be accessible through the internet. Such
computers can be installed for example at the customer's location
or at other accredited metrological laboratories to which the
certificate data can be transmitted. Through the data connection
12, the identification code acquired by the reader device 6 can be
transmitted directly, i.e. without intermediate storage in the
database 8, to a processor at a remote location (not illustrated).
A further data connection, for example to a balance on which
calibration checks are performed (not shown), allows data from this
checking balance, for example weighing result data, to be
transmitted to the processor 11 of the computer 7, or data from the
computer 7, for example certificate data, to be transmitted to the
checking balance. Further systems configurations are also
conceivable.
[0053] The flowchart diagram in FIG. 5 shows the time sequence of a
routine test for the checking of a balance with a weight piece 1
that is marked as described herein. The machine-readable
identification code on the weight piece 1, for example in the form
of a matrix code 2 as shown in FIG. 2, is used here for the purpose
of verification and validation. For example, it is possible to
ascertain whether the specific weight piece 1 matches the weight
piece described in the checking procedures, which could be
internally generated or externally mandated procedures.
[0054] A program which is executed in the processor of the balance
controls the process of the weighing check and instructs the user
accordingly. As a first step following the start, the weight piece
1 is presented to a reader device 6 which reads the matrix code 2
and compares the corresponding identification code to the data
which are stored in the computer 7 for the weighing check. The
computer 7 can be a computer set up separately from the balance, or
it can be incorporated in the balance where it can be constituted
essentially by the processor of the balance. If the identification
code matches the code data of a permissible, i.e. registered,
weight piece 1, the weight-checking process is allowed to proceed
and the routine test can be continued. If no match is found for the
identification code, the weight-checking process is aborted and a
failure message is issued. A record of the outcome can be produced
by a printer that is connected to the balance and/or to the
computer 7. It is also conceivable that a corresponding entry is
made in the database 8 that is connected to the computer 7.
[0055] The drawing figures represent a schematic illustration of
embodiments that are meant only as examples. Different kinds of
markings are also conceivable as well as different arrangements of
the markings on the individual weight pieces. It is also possible
to include any other desired items of information in the code for
the purpose of making the central traceability system more
comprehensive.
* * * * *