| A short introduction of what you should know about scales, balances, weighing, calibration and verification. The below mentioned information is not a full description, but it will help you to get an overview of the large range of topics around scales and balances.
Absolute weighing: Establishing the weight of an item in milligrammes (mg), grammes (g), kilogrammes (kg) or tons (t). If no arrangement has been made, the conventional weighing value will be quoted.
Accreditation of DKD laboratory: Examination and appraisal of a metrology laboratory with a view for authorisation to produce internationally recognised DKD calibration. After successful appraisal and examination PTB, represented by DKD in the German Accreditation Council, will issue the accreditation certificate.
Adjusting: Exact setting of measured variable of a measuring equipment (e.g. balance) by means of expert intervention in the measuring system.
Adjusting the weighing area of balances: either using an external examination weight via the adjustment programme (CAL) or by means of automatic internal adjustment or adjustment circuit. Necessary following changes in temperature, changes in environmental conditions, location changes, etc. Daily routine check is recommended.
Apportioning / sequence weighing: Balances with tolerance area. Upper and lower limiting values are programmed individually, either using weights or numerically by means of the keyboard. During apportioning/sequence weighing a luminous beam moves between the limiting values and is supported by an acoustic signal. Overdosing and underdosing are prevented or parts, that are too light or too heavy, can be extracted immediately. Limiting value input in grammes (g), number of items or in percentages (%) is possible.
Approval of a balance: This is granted by a federal institution, e.g. PTB A balance can only be gauged if a qualification approval is available.
Balances appropriate for verification/not appropriate for verification: Almost identical from the metrology point of view. Some details are prescribed legally for balances appropriate for verification, e.g. alterations to software, additional inscriptions.
Balance error limits: Concerns gauged balances. Error limits are to be understood as the permissible tolerance, thus the permissible deviation of weight according to plus and minus. They are load controlled, definition in the weights and measures regulations. One distinguishes between the error limits during initial gauging and the traffic error limits
Build-up time of balances: Time necessary for determining weight
Buoyancy of the air: Everybody experiences buoyancy in the air (weight loss), that is not to be neglected during very exact weighings.
The conventional measured value of weight was introduced in order to neutralise this in practice. The buoyancy of the air must, however, be taken into consideration because it influences on the weighing indicator.
Calibrating balances: Determining the correction of measured variable of a measuring equipment (e.g. balance) without intervention in the measuring system. Example: Checking a balance by positioning a test weight. The term "calibrating" was also formerly used for adjusting.
Calibration document or certificate of balance calibration: Documents the metrologic features of a balance or a weight as well as tracing back to the national normal. Extra charge.
Calibration value: Measurement for the gauging tolerance; between 1 and 10 depending on the balance.
Capacity indicator: An ascending illuminous row in the balance display unit that indicates the occupied weighing area and that this area is still available. Protects against unintentionally exceeding of the weighing area.
Carat, metric: One metric carat 1 ct = 0.2 g. It is used to determine the weight of precious stones.
Certification according to DIN EN ISO 9001: Certification is issued if, for example, a company provides the proof that it has implemented all the requirements of the quality management system according to DIN EN ISO 9001.
After successful completion of several audits the company receives a certificate according to the DIN EN ISO 9001 quality management system.This certificate differs completely from a DKD calibration certificate, that certifies the metrologic features of measuring equipment (e.g. of a balance or of a weight).
Certification according to DIN EN ISO 9001 is also not identical to the accreditation, as no statements with internationally recognised effect are connected with this.
Certificate of conformity: The conformity of balances appropriate for verification with the qualification approval is documented by the Office of Weights and Measures (named office) by issuing the certificate of conformity in the course of gauging.
Characteristic line of a balance: Graphic presentation of the weight indication of balances when burdened with test weights. From zero to the biggest load. Conclusions regarding the accuracy of the balance can be drawn from the course of the characteristic line.
Commercial balances: Balances belonging to gauging class III. The shop balances are the most frequent representative.
Commercial weights: Weights belonging to the M3 OIML error limit class M3
Conventional measured value of weight of a weight: Effect of a weight on balances under the following idealised conditions: Material density of the weight 8000 kg/m³, reference temperature 20°C, atmospheric density during measurement 1.2 kg/m³. Also see buoyancy of the air.
The conventional measured value of weight simplifies very exact weighings, as fluctuations in atmospheric density up to +/- 10% do not now have to be taken into consideration by way of calculation. This has asserted itself all around the world. All weights have been adjusted to the conventional measured value of weight.
Corner load examination of balances: Examination of balances by means of eccentric placing of a test load outside the centre of the weighing plate.
Data interface / Parameter: Normally RS 232C. For direct connection of printer or PC to the balance. The setting of the interface parameters, baud rate, parity, data bits are carried out by means of the balance keyboard following the operating instructions.
Declaration of conformity for scales and balances: The declaration of conformity proves that a product meets EU regulations. If it concerns electronic balances, this comes always with CE sign. The declaration of conformity is printed in the operating instructions.
Differential weighing: Determining the difference in weight of an item to be weighed before and after treatment, for example drying. Both weighings are carried out using the same balance and under the same conditions.
DKD: Metrology laboratories that have accreditation for a certain measured variable are united within the German Calibration Service (DKD). They have a high degree of metrology competence.
A laboratory with DKD accreditation has the right to issue internationally recognised calibration certificates for the measured variable. The DKD certificates are valid in many countries of the world, for example throughout the European Union
EA: European co-operation for Accreditation (formerly WECC or EAL). Regulates the international mutual recognition of DKD certificates.
Earth's pull: This has a considerable effect on the accuracy of electronic balances. As its strength differs in every place on earth, balances adjustment depends on location.
Electromagnetic dynamic compensation: Electronic analysis balances and high-quality precision balances which work according to this measuring principle. This is based on the physical impact of a dynamic effect that a current-carrying coil in a permanent magnetic field undergoes.
Error limits on weights / error limit classes: The error limit of a weight is in accordance with the permissible tolerance, hence with the largest, permissible deviation from nominal value according to plus and minus.The error limit classes for weights are graded in strict hierarchy and defined in the OIML.
External test weight: (formerly calibration weight) Used to adjust or check balance accuracy. Adjustment of the weighing range. The external test weight can subsequently be DKD certified at any time.
Filter for adaptation to the environmental conditions: Jarring is filtered out by increasing the number of internal balances measuring cycles, i. e. the integration period is extended. Additional safety by means of the standstill control that prevents a measured variable being read off or printed out too soon. Several filter stages can normally be set. Also see measured value of weight.
Finished package control (FPVO): This regulates the correct filling of readily packed products to the weighted-in quantity shown on the packing (filling weight). The permissible tolerance are regulated by the calibration act.
High-resolution balances: Normally understood as analysis balances and precision balances with a resolution of 100,000 digits. The resolution is the result of the weighing area: readability d
Example: weighing area 300 g, readability from 0.001 g appropriate to 1 mg, resolution = 300,000 digits
Industrial balances: This term has a very wide range. It is understood to include table balances, platform balances, control balances, suspended balances (crane balances), container balances and other types.
Internal test weight: Same as external test weight, however installed in the balance and motor powered.
International kilogramme prototype: Also called "original kilogramme" and is the basic mass unit. This weight of 1 kilogramme is kept in Paris. It is globally binding for the metric measurement system. The grammes (g), milligrammes (mg) and tons (t) are derived from this.
ISO 9000ff: Quality management system in the form of a DIN standard for quality assurance within a company. Full name DIN EN ISO 9000ff-xx
ISO/GLPP protocol: Print-outs of weighing results (crude values) as well as print-outs of the correct balance adjustment with details of date, time and balance identification are required in quality assurance systems. The most simple method is by means of a connected printer.
Laboratory balances: This is for standing for analysis balances and precision balances.
LCD display (Liquid Cristal Display): Structural member for the digital weight display. The anisotropic conductibility of liquid crystals is used in liquid crystal display. The LCD display is not luminous.
LED display (Light Emitting Diode): Structural member for the digital weight display. The light diode's or the luminous diode's own luminosity is used. The LED display is luminous.
Linearity / Correctness: Greatest deviation of the weight display to the value of the test weight according to plus and minus over the entire weighing range. Upper limit +/- 3 d. Quality feature.
Mass: The body mass is a physical size. It is a measurement for the influence of inertia against a change in speed, and also the attractive power on other bodies. The mass is always the same, irrespective of the earth's pull and the buoyancy of the air. The metric unit "kilogramme" is also applicable to the mass.
Measured value of weight: Display on the balance after the build-up procedure has ceased. This is mostly indicated by lighting up of the weight unit (g)/(kg). The weighing result can now be read off or printed out correctly.
Measuring uncertainty of a balance: The measuring uncertainty identifies the area in which the actual measured variable is to be found. The probability of this is at least 95% in DKD. It is determined individually for every balance according to an exactly prescribed examination procedure and documented in the calibration document. It dependsnon various internal and external balance factors. The measurement uncertainty rises with the increasing load on the balance.
Microbalances: Analysis balance with a maximum load between 5 g and 50 g. Readability d = 0.001 mg or better.
Minimum load of balances and scales: Lower limit of the weighing range appropriate for verification. This is noted on the gauging plate. The balance continues to function even below the minimum load.
Multirange balance: Balance with different weight range. Every weight range starts at zero, the largest weight range stops at the highest balance load. Every weighing range has its own readability d.
Newton: The Newton unit (N) is the unit of force in the international unitary system (SI). It is the force that accelerates a Mass body of 1 kg by 1m/sec².
Net total: Possibility of depositing the container weight in a separate balance memory when producing recipes. The net total is the total weight of all weighted-in components (excluding container weight) and is indicated on the balance upon key depression. Serves as a control method at the end of a recipe.
Net weight: Weight of an item to be weighed after deduction of its packaging and/or transport container
Non-automatic balance: Intervention by operating personnel is necessary in order to operate this balance. This applies to the complete balance range. This term is used in particular with regard to balances appropriate for verification
OIML: Organisation Internationale de Métrologie Légale. This organisation regulates metrologic concerns in legal weighing (metrology).
Overload / Underload display: Seen in the display unit of a balance in cases of overloading or underloading.
Percentage determination: Example: Reference weight of a sample before drying 50g = balance display 100%. After drying 40 g = balance display 80% absolute (dry mass) or 20% relative (humidity).
Piece numbers of individual parts: If one weighs for example 10 of the same parts, the reference piece number is 10. The balance now automatically forms the average weight of each part. From this point onward the same parts to be counted are shown as piece numbers. The following applies in this case: The higher the number of reference pieces, the greater the counting accuracy.
Plus-Minus weighings: e.g. for quality control purposes: Burden balance with target weight - counterbalance by pressing the TARE button (target weight is stored) - balance now only shows deviations from target weight during subsequent weighings according to the preceding sign.
Precision weights: Weights of the OIML middle error limit class. They are used for the examination of precision balances and industrial balances.
Producing recipes: Weighing in of various components to form a mixture in a receptacle, for example according to a recipe >> net total
Protective system IP: The higher the number, the smaller the amount of dust and splash water that is able to penetrate the balance housing. IP 54 is a standard on higher-quality balances.
PTB: Physikalisch Technische Bundesanstalt in Brunswick. This Federal Authority is responsible for the legal weights and measures body, OIML in Germany. They regulate gauging measures for balances.
Readability d: Smallest readable weight value
Recalibration: Periodic remeasuring of a measuring/testing medium (e.g. balances/weights) in order to monitor correctness
Reference number of pieces: Number of pieces necessary in order to obtain a representative >> reference weight during piece counting. Mostly between 5 and 50 pieces
Reference weight: Representative part weight used in piece counting of same parts. Mostly gained from the average formation of several parts >> Reference number of pieces
Reproducibility: (standard deviation) Measurement of compatibility during repeated measurements (e.g. balance) under the same conditions. Mostly 1 d or smaller. Quality feature
Semimicro balance: Analysis balance with readability of d = 0.01 mg.
Stand-by balance: Only partially switched off if not in use. Does not therefore need warming-up time when switched on again. Time saving.
Tare: Possibility of setting the weight display of a container standing on the weighing plate back to zero. Can be repeated as often as required on electronic balances. Tare is subtractable, i.e. the available weighing range is reduced by the tare weight. Example: Weighing range max. 6000 g, tare (=container) 470 g, available weighing range = 5530 g.
Tare weight: Weight of the packaging of an item to be weighed or a transport container or a container in general. Also see >> gross weight, >> net weight
Temperature influence on balances: This is of a physical nature and can only be partially corrected by fitted compensators. It is therefore necessary to >> rejust the balance after a change in temperature.
Temperature range: Range in which a gauged balance may be used. This is shown on the identification plate. If this is exceeded or fallen short of, measurement errors are possible.
Test medium monitoring: Required in the quality management system according to ISO 9000ff as well as GLP. Means of measuring (e.g. balances) and test medium (e.g. weights) must be checked for correctness at defined intervals, i.e. calibrated. This examination is to be documented.
Tolerance of measuring equipment: Each piece of measuring equipment has an display tolerance of a physical nature. The tolerance defines the largest permissible deviation of the display according to plus and minus. Also see >> Error limits
Tracing back to the national normal: The ISO 9000 standard requires that all testing medium (e.g. weights) conform to the official standard in accordance with the defined tolerance. Also see >> International kilogramme prototype
Traffic error limits: These amount to double the >> error limits of a balance during initial gauging (initial gauging error limits). They are the permissible deviations when using a balance according to plus and minus.
Validation of balances and scales: Documented proof that to a high degree of certainty a process or procedure is suitable to fulfil a specific task.
Verification: Documented proof that a prescribed requirement has been fulfilled.
Verification period of validity for balances: Analysis balances verification class I 2 years precision balances gauging class II 2 years industrial balances gauging class III 2 years control balances, all classes 1 year.
Verification period of validity for weights: Weights belonging to error limit class E2 4 years weights belonging to error limit class F1, F2 4 years weights belonging to error limit class M1-M3 4 years control weights, all classes 1 year
Warming-up time: The period of time between switching the balance on and reaching the operating temperature. Normally quoted in the operating instructions. Also see >> Changes in temperature
Weighted-in quantity: If a precisely defined substance quantity is required for a process, this substance is weighted into the desired weight value.
Weighted-out quantity: If a substance quantity is precisely defined in advance for a process and is subjected to an alteration, e.g. drying, the remaining weight of the substance is determined after process handling by means of the weighted-out quantity (also known as return weighing).
Weighing range, max.: Working range of the balance. The balance is loadable up to the stated weight value as upper limit.
Weighing table: Analysis balances and high-resolution precision balances must be installed in places where they cannot be jarred. Sturdy stone plates are suitable for this purpose that either rest on wall consoles or on solid table bases. They may not change their horizontal position even when pressure is applied to the stone plate.
Windbreak: Protective device in order to protect the weighing plate against disruptive movements of the air. Necessary on precision balances with readability of d < 10 mg. Always present on analysis balances.