Weighing and inspection Wiki

The ATEX directives consists of two EU directives describing the minimum safety requirements of the workplace and equipment used in explosive atmosphere. ATEX derives its name from "Appareils destinés à être utilisés en ATmosphères EXplosives" (French for Equipment intended for use in EXplosive ATmospheres).

• Accuracy is a qualitative term describing the correlation of a measured quantity with its true value. Systematic and Random Errors are more suitable for evaluating metrological equipment like scales. Since the systematic error is correctable, “accuracy” is often used in practice to designate the Random Error or Imprecision Range of a measuring device.
• Accuracy is of critical importance to a scale’s performance because poor accuracy contributes to not only incorrect results, but also lost revenue, increased service and labor costs, and decreased quality of the overall product.
• A large number of factors affect accuracy:​
  • Environmental​ (temperature fluctuations​, air pressure​, magnets​, vibrations, electrical interference​, humidity​, wash-down areas​, destructive chemicals and debris)
  • Design of the vessel and platform (must be level and strong – no deflections)​
  • The electronics and cable connections can be affected easily by noise and other electrical interferences and moisture.​
• Accuracy is quantified by an instruments readability, standard deviation, resolution, accuracy class or the uncertainty of measurement given (e.g. in a calibration certificate). ​Accuracy of a process vessel scale is the result of mechanical conditions and a good measuring chain

The accuracy class is the classification based on various factors which, according to the internationally recognised recommendation OIML R60 are standardised for accuracy classes. These factors are: Linearity deviation, hysteresis, temperature influence on the characteristic value, reproducibility, load creep and temperature coefficient of the minimum preload signal. The accuracy class is classified in the OIML R60 based on the errors. Common accuracy classes for single point load cells are C3, C6 or C3MR. The letter C indicates that the load cells are suitable for Class III legal-for-trade scales as a maximum. The number indicates the maximum number of steps that can be calibrated of the scale: C3: 3000 steps, C6 6000 steps C3MR: Multi-range scale with maximum 2 x 3000 steps.

• Setting a weighing instrument to eliminate discrepancies between the value on the readout and the actual value for the mass on the weighing instrument (balance).
• Adjusting a weighing instrument so that the deviation between the displayed value and the true mass is reduced as much as possible, and, at the very least, the instruments maximum permissible errors are not exceeded. Many high-resolution balances have a built-in weight, which can be either automatically or manually placed on the load receptor. ​It is especially necessary to re-adjust the sensitivity of high-resolution balances each time they have been moved to a different location. ​

• Allowing an object sufficient time to reach the same temperature as that of the weighing instrument is also necessary in order for the adsorptive layer of moisture on the surface of the object to equilibrate.
• Particularly when small objects are weighed on a high- resolution scale, this essential requirement must be met to obtain reproducible weighing results.
• To minimize an object´s adsorption of humidity, users must avoid soiling or otherwise touching the object with their hands, for example, as this leaves fingerprints, which can affect the weighing result.

To minimize forces due to air currents (drafts), the flow rate of the ambient air must be kept to a minimum. A draft shield serves this purpose. For scales with a readability of 1 mg, an open draft shield, e.g., in the shape of a glass cylinder, will generally suffice. Scales with a readability equal to or below 0.1 mg require a close draft shield. Contrary to practical considerations, a draft shield should be as small as possible from metrological viewpoint, because internal drafts can be generated within a large draft shield chamber. Convection currents are produced, particularly when an object to be weighed is not at exactly the same temperature as that of the weighing instrument. These currents make objects that are hotter than the ambient temperature appear to be lighter and those that are colder, heavier. Therefore, it is still important to condition an object to the same temperature of the scale as in the past.

Alternating Current (AC) refers to electrical current that regularly changes its direction such that the momentary positive and negative values cancel each other and the average of the current over time is zero

Ambient influences may affect the detection result. The following measures should be used to avoid or minimise disruptive ambient influences:

• Power Supply
• One-sided heating
• Foreign metals
• Electrostatic discharge / conveyor belts
• Electromagnetism
• Vibrations
• Insulation

• They automatically check products of the same weight (packages, pieces etc.) for deviations from the correct weight (nominal filling quantities, unit weight) and can also sort out products if they exceed or fall below user-defined weight limits as well as sort them into weight classes. They check every product weighed.
• Automatic Checkweigher for Single Weighing (ACS): Automatic scale that determines the mass of specified individual loads (e.g. finished packaging) or of individual loads of loose materials. 
• Automatic Checkweigher for Weighing (ACW): Automatic scale that fills containers with a specified and effectively constant mass of bulk. 

• A weighing instrument that does not require the intervention of an operator during weighing. ​
• Example: a checkweigher integrated into a conveyor belt.

• Scales that perform the weighing process without intervention of operating personnel by initiating a device-characteristic, automatic sequence.
• Floor scales with large platform areas can either be free-standing on the floor or installed in a pit. With large platform areas, floor scales are particularly suitable for applications where heavy and voluminous loads must be weighed.

The readout is automatically set to zero by the balance, to eliminate minor deviations and correct any slow zero point drift.

• Analog indicator: Device for interpolation between two scale marks.
• Digital display: An additional, specially identifiable, numeric display with a scale interval less than the verification scale interval "e" (on weighing instruments acceptable for legal verification)

Unit of measure for the modulation rate of electrical signals, often equated today with the unit bits|second for transmission speeds of payload data.

The belt speed v (in m/s) indicates the speed at which the products are conveyed over the scale.

• Scales that are implemented into a conveyor belt and weigh bulkgoods transported on the conveyor belt.
• Mistakenly, automatic checkweighers are often referred to as “beltweighers”, since they use a conveyor belt to transport the packaged goods.

Bench and floor scales for industrial use can be divided into different categories: Complete or compact scales contain a display and evaluation unit in addition to the actual load cell or weighing system, on which the weighing results are displayed. Minebea also offers Intec weighing platforms and floor scales, which are used for weighing, but are delivered without a display unit or associated weighing electronics. These can be connected directly to a PC or PLC system via a serial interface. Complete and compact scales can be connected to various peripheral devices or other systems via a variety of serial interfaces, RS 232, RS 485, fieldbus interfaces or Ethernet TCP/IP.

There are also scales that are suitable for special applications, such as the IU pallet scale, which can weigh pallets from 300 to 3,000 kilograms. If particularly precise measurement results are required, Minebea Intec has high-resolution scales in its portfolio, such as the IS (Industry Supreme) weighing platform, with extremely high resolutions of up to 620,000 display steps, thus giving it a greater accuracy and minimising product loss.

Floor scales with large platform areas can either be free-standing on the floor or installed in a pit. With large platform areas, floor scales are particularly suitable for applications where heavy and voluminous loads must be weighed. If the application requires the lowest possible platform height, an IF flat-bed scale is also recommended. These scales can be easily loaded with goods to be weighed, e.g. by means of a lift truck, without the need for pit installation. All bench and floor scales are also available as legal-for-trade versions and/or as versions with Ex approval for use in hazardous areas.

Read more "Bench and Floor Scales"

The BRC Global Standard Food, Version 5, is a companion to the IFS standard required in the rest of Europe. Both the BRC and IFS are represented and recognised as standards in the GFSI (Global Food Safety Initiative).

The CE mark indicated the marked instrument conforms to all applicable European Directives. The following are applicable for weighing instruments: Low Voltage Directive 2006/95/EC (where applicable), EMC Directive 2014/30/EU, Directive on Non-Automatic Weighing Instruments 2009/23/EC (where applicable), ATEX 95 Directive 94/9/EC (where applicable), Measuring Instruments Directive 2004/22/EC (where applicable), Machinery Directive 2006/42/EC (where applicable), and others.

Calibration determines the relationship between the displayed value and true mass by comparison with a known mass. ​During calibration no intervention occurs which would change the parameters of the weighing instrument (If such a intervention does occur, this is referred to as “Adjustment”).  ​

The ability of a scale to keep the reading constant with an unchanged load during an operating time within specified limits.

A dynamic checkweigher, also known as a checkweigher, automatic scale or erroneously called a "belt weigher" (bulk material weighing), is used in the production of piece goods to monitor, sort (classify) or even influence (weight-wise) them according to weight criteria, e.g. according to FPV (local finished packaging regulation), by direct corrective feedback control (trend controller, trend control) of filling machines. This is a fully automatic weighing of all produced products (100% control), where the products are weighed over the weighing conveyor belt, without stopping, i.e. in dynamic condition. In this case, it is not the scale, but the production speed that determines the period of time when the scale must output a weight value. Dynamic checkweighers are permanently integrated into a production line and check the products in production at throughput rates of usually 20 to 200/min, maximum even 600/min). There are different types of checkweigher: depending on where they are used, they are classified as in-line or end-of-line checkweighers. There are also multi-track checkweighers if the filling and packaging machines deliver the products in parallel on several tracks due to very high capacity requirements. Combination units that combine a checkweigher with a metal detector (critical control point, CCP) offer a space-saving solution, as they simultaneously use the required weighing infeed belt for metal detection.

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The characteristic of metal, which allows it to generate an eddy current, is known as “conductivity”. Put simply: the ability of metal to conduct electricity.

• The conventional mass of an object is equal to the mass of a standard with a density of 8,000 kg/m3, which keeps this object in equilibrium at 20°C and an air density of 1.2 kg/m3. For objects with a deisity of 8,000 kg/m3 (= 8.0 g/cm3), the conventional mass and the mass of this object are identical.
• Today, weights that deviate form a density of 8,000 kg/m3 are adjusted so that at a standard air density of 1.2 kg/m3, they have the same effect as do weights with a density of 8,000 kg/m3.
• The introduction of the conventional mass is advantageous in that the air buoyancy correction formula can always be used with the value ρ_s= 8,000 kg/m3, irrespective of the true density of the standard weights.

• The conventional weight of a body is equal to the mass of a mass standard that has a density of 8 g/cm-3, which keeps this body in equilibrium at 20°C, and an air density of 1.2 mg/cm-3. If a body has a density of 8 g/cm-3, its conventional weight and its mass are identical.

• Metal detectors are able to guarantee consistent detection sensitivity over a large range of conveyor speeds. Only in the event of conveyor speeds of less than approx. 0.05 m/ s (e.g. in the case of wide conveyor belts with lots of products positioned in parallel) or more than approx. 20 m/ s (e.g. in the case of overpressure or vacuum tube transport) is it possible that the attainable detection sensitivities will differ from normal values.
• In the case of discontinuous conveyor speeds (e.g. stop & go operation), it must be considered that there will therefore be reduced detection sensitivity when the critical conveyor speed is not met.

• Abbreviation for “Deutscher Kalibrierdienst” (German Calibration Service). The DKD consists of numerous calibration laboratories, which are accredited (i.e., tested, approved and audited) by the PTB (German Federal Institute of Physics and Metrology) and recognized for certain quantities to be measured and for testing measuring instruments (e.g., balances or scales) or “material measures” (e.g., weights).
• Each laboratory compares these instrument readouts or weights with mass standards and issues a DKD calibration certificate, which specifies the result.
• DKD certificates are recognized throughout key industrialized countries

The dead load or preload indicates the “moving masses” of a metrological system as a whole. It designates the masses that must be weighed together. This includes, among others, superstructures like weighing pans (non-automatic weighing instruments) or conveyor belts (automatic weighing instruments). Due to the relatively heavy superstructures that are part of motorized transport systems, weigh cells for automatic scales in particular must also be capable of operating with a very large dead load, which is often significantly higher than the actual load range of the scale

If the load exceeds the destructive load, there is a risk of mechanical destruction of the load cell. Subsequently, measurement is no longer possible

The detectability of metal objects depends on the position in which the metal particles go through the detector tunnel. A ball always has the same geometric proportions, no matter which direction it is facing. However, a metal part that is not symmetric, such as a piece of wire, will cause smaller or larger signals depending on how many “field lines” are influenced.

• The resolutions available on the market for standard detectors are between 0.1 mm and 1.6 mm. The selection of resolutions leads to the supposition that a lower detector resolution leads to better detection sensitivity.
• This hypothesis can only be confirmed in part: if a 0.4 mm detector is compared to a 0.1 mm detector, the latter has an area that is four times smaller but needs four times the X-ray energy to generate an image of comparable quality. If the same amount of energy is used in both cases, comparable quality can only be achieved with a significantly reduced throughput.
• In practice, detector resolutions of 0.4 mm to 0.8 mm have become accepted.

The detector sensitivity of a metal detector within the tunnel shaped opening is not homogeneous. This is due to the field distribution in the detector tunnel the proximity to the transmitter/receiver. The detection sensitivity decreases at a distance from the transmitter/receiver.

Abbreviated term for scale interval (refer to “Scale interval”).

Filters are used to suppress interference and to reach a stable measurement value. Scales usually use low pass filters that suppress higher frequency interference. Currently, signal processing is more and more being carried out digitally rather than using analog processing. The advantages are flexible applications, higher accuracy and reproducibility as well as lower sensitivity to interference.

The value of the smallest change in load that is gently added or removed from the weighing pan and that results in a perceptible change in the readout displayed.

A quantity that is not the subject of a measurement, but influences the weighing result, and is outside the specified rated operating conditions of the instrument.

Slow change, over time, of the readout with a constant load on the balance.

See “Checkweigher”

This error is also referred to as “corner load error”. This is a change in the readout when the same object is places in various positions on the weighing pan.

A counterforce created by means of a current-carrying coil in a permanent magnet is the same as the weight force of the product on the weight receiver, which is connected to the coil via a lever system. The coil current is regulated with an analog or digital controller by a sensitive position sensor such that the lever always stays in neutral position. The measured value is then proportional to the coil current. Electromagnetic balances are suited for high-resolution and high-speed weighing.

Are generated when non-conductive objects or containers (such as glass or plastic) are electrically charged, for example, by pouring from one container to the other. Static electricity can be prevented by maintaining sufficient air humidity or by using an electrically conductive metal enclosure that is connected to the weighing pan. Electrostatic forces show up as a drift in the weight readouts and in the resultant poor reproducibility of the values measured in repeated weighing procedures.

Difference between the displayed value and the true or reference value (often called deviation).

The FMEA methodology has proven to be a successful approach to conducting a hazard analysis. FMEA stands for “Failure Mode and Effects Analysis”

A concentration of the magnetic field lines caused by all ferromagnetic metals (iron) and ferrites.

In the case of diamagnetic and paramagnetic metals (stainless steels and non-ferrous metals) there is no field concentration due to the permeability. In fact, the alternating field of the transmitter induces a voltage in these metals. A current forms depending on the electrical conductivity; in this context we also refer to “eddy current formation”, which in turn creates a magnetic field

• The X-ray source dimension (‘focal spot’) is determined by the size of the electron beam when it strikes the anode. It can affect the detection result.
• If the foreign body is radiated with a broad light source, the result is a ‘blurry’ transition between the core shadow and the light areas. This transition is called the penumbra (see figure).
• A small X-ray source, by way of comparison, leads to a sharp-edged shadow and therefore sharper image definition.

Force, or weight, on the one hand, and mass, on the other hand, must not be confused: Force is the effect on an object that deforms or accelerates it (e.g., during free fall). Mass is a property of an object, describing its quantity. There is an additional difference between force and mass: To describe a force, its size and its direction of action must be defined. This is unlike mass, where defining its size suffices. The units of measure for mass and force are likewise different. Mass is measured in kg, whereas force is measured in Newton (abbreviated „N“), where 1 N = 1 kg · m/s2.

First and foremost is the protection of humans: Contaminated goods are detected and ejected by the systems; consumer protection is the most important asset here. Furthermore, machines in production chains are also protected by the detectors: Foreign bodies in the product stream can cause machines to be damaged during further processing. Legal regulations also make the use of such devices mandatory for the plant manufacturer in some cases.

The systems can detect various types of foreign bodies. A distinction is made between metal detectors and X-ray inspection systems. Industrial metal detectors are based on a coil that generates an electromagnetic field in the search tunnel. Each passing product leaves a specific pattern. As soon as deviations are detected, this indicates contamination. Special round coils such as Vistus Freefall detect foreign objects in the falling product stream, such as bulk materials, snack food for example. With the Flexus® Combi, Minebea Intec even offers a combination of checkweigher and metal detector: This gives users maximum quality control in a minimum of space.

read more "Foreign Body Detectors"

A foreign body is a physical contamination in a product. These bodies can have a physical or chemical impact on the product quality and can pose a risk to the consumers. Examples are stones between fruits, wires or metal fragments in salad or broken glass in jam.

• The GFSI was set up in 2000. In April, the directors of a group of commercial enterprises operating internationally agreed at a conference that consumer confidence in foods and food safety needed to be increased.
• The aim of the initiative is to continually improve quality management systems in the area of food safety, cost efficiency in the supply chain and, above all, food safety for consumers around the world.

• The acceleration imparted to an object by attraction due to gravity. ​Gravitational accelleration depends on the location: Due to centrifugal force, it is less at the equator than at the poles of the earth. ​It also decreases as the altitude increases. The mean value for g on earth is 9.8 m/sec². ​Gravitational acceleration is simultaneously the proportionality factor between the weight "W" and the mass “m” of a body: W = m . g. ​
• Other terms for g: “acceleration of gravity”, “acceleration of free fall”, “apparent gravity”, “earths attraction”.

Gravity is the force that pulls objects to Earth. It is often assumed to be the same everywhere on our planet, but it varies because the planet is not perfectly spherical or evenly dense. In addition, gravity at the equator is weaker due to centrifugal forces. The same applies to places that are at a greater distance from the center of the Earth.

One aim of HACCP is to protect consumer health by avoiding foreign body contaminations. In this case, it is sensible to check packaged products or products shortly before packaging if this has advantages in relation to the ability to detect foreign bodies (on the basis of the hazard analysis).

• Hysteresis means that at a constant load, the displayed value depends on the previous load.​ Quantitatively, hysteresis is expressed as the difference between the readouts obtained when the same load is weighed once following a lighter load and once following a heavier load.  ​
• In terms of weighing instruments hysteresis occurs particularly with strain-gauge load cells and weighing instruments subject to mechanical friction.

In autumn 2001, German business decided to develop its own standard for the auditing of private brand manufacturers and to submit this standard to the GFSI. The IFS is now the most widely used standard in Europe. In principle, the IFS does not require that a detector is installed in the process. This depends on the result of the risk analysis. This is in comparison with the BRC (British Retail Consortium), where a detector is mandatory. In this case it would be necessary to prove that there was no risk in order to be granted a derogation.

Degrees of protection, indicated by the abbreviation IP (International Protection) and two reference numbers, specifying the degree of protection of electrical equipment against contact an ingress of solid foreign bodies or dust (the first number) and water (the second number). ​For instance a IP65-protected balance is dust-tight and completely protected against contact with live components (1st reference number:6). This balance is also protected against moderate jets of water projected against it from any direction (2nd reference number 5).

The infeed belt is the connecting part between the device feeder and the weighing belt. The belt speed is identical to that of the weighing belt. The transition from the device feeder to the infeed belt of the scale should be set up so that the transition is smooth and the product direction does not change. Thereby, the product must not tilt, tumble or topple over. It is imperative to avoid a “sloshing” of liquid product contents. In general, the transition between the belts is critical if the product length drops to less than twice the roller diameter. In such cases, the transition may be improved by using transition plates or rollers.

Quantity that is not the subject of a measurement, but that affects its result.

• The time during which the instantaneous weighing signal is totaled and averaged in a weighing instrument. ​
• A long integration time yields good results in suppressing interference, a short integration time allows rapid response to changes.

An interfering factor is an influencing variable whose value is within the respective requirements of specified limits, but outside the specified nominal operating conditions of the measuring device. An influencing variable is considered an interfering factor if there are no stated nominal operating conditions for this influencing variable. 

Most balances today come equipped with this type of fully automatic calibration/adjust-ment function, activated at specific or at user-defined intervals. In addition, when a defined temperature difference is exceeded, the calibration/adjustment procedure is triggered automatically. This makes it possible to ensure the accuracy of the balance without operator intervention.

• Device used as a guide to find the horizontal position of a balance or scale. ​
• Usually consists of a small, liquid-filled, slightly curved container in which an air bubble shows the highest point.

• The deviation from the theoretically straigt-lined linear slope of two interdependent values. ​
• For weighing instruments, this means the positive or negative deviation of the readout from the actual load, when the zero point and the span have been correctly adjusted. ​

There are different types of Load Cell errors that can occur:

• Temperature error: Deviation from the ideal line (either as offset or as slope error)
• Linearity error: Deviation from the ideal line, will be maximum at half load
• Hysteresis error: Deviation from the ideal line at stepwise loading and unloading
• Creep error: Deviation from the ideal line over a period of time
• Repeatability error: Variations of measurements around an ideal line at several weighing cycles

A load cell is used to determine mass: The weight force exerted by the sample is converted into an electrical signal by the load cell. Load cells are therefore the most important components of an electronic scale. One of the most widely used technologies is based on strain gauge technology: an analog load cell consists of a measuring element (so-called spring body) made of steel or aluminum, on which a strain gauge (Wheatstone bridge) is mounted. Each electronic scale has an integrated load cell that ensures that a weight can be measured.

DMS load cells are the most widely used, but there are other technologies for weight determination in weighing technology such as EMFC, electromagnetic force compensation, in which mass determination takes place completely without friction loss. Generally, load cells are installed in industrial plants, such as filling plants, weighing silos or checking the filling level of tanks.

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• The previous role of the state as inspector and certification body has been taken over by what are called accredited bodies (AB). They are not only responsible for the certification of products, but also for the approval and monitoring of quality management systems; they are assigned these tasks by the competent national ministries.
• A variety of measuring device types have to meet the requirements of the European Measuring Instruments Directive. Automatic weighing instruments are classified as measuring device type MI-006.

A current through a conductive part generates a magnetic alternating field

Mass, a physical quantity, is a measure of the amount of material in an object. The unit of measure for mass is the kilogram (kg). Mass describes the property of an object. This property is revealed not only in the inertia of an object in changing its momentum (acceleration or deceleration), but also in the force of attraction between two objects. Thus, in the earth‘s field of gravity, each object is subject to a force. 

W = m · g

m = mass, g = local gravitational acceleration

Mass comparator is a common term for extremely accurate balances used for comparing weights. Often these instruments have a limited weighing range that does not start at zero, and very high readability. For instance: from 9.9900000kg to 10.0500000kg for a comparator that is used for 10kg weights.

Physical quantity, a base unit of the international system of units (SI).

A device intended to reproduce or supply, in a permanent manner during its use, one or more known values of a given quantity.​

Maximum capacity is the upper limit of the weighing range. ​It does not take into account the additive tare capacity of a tare device (see “Taring”). 

• Limits of error of a legally verified weighing instrument, which must not be exceeded when this instrument is operated. ​
• The max. perm. errors in service are twice the maximum permissible errors on initial and subsequent verification.

• Limits established in a table for the errors of measurement of a weighing instrument. ​
• These must not be exceeded during verification

Difference between the value displayed by the scale and the true value of the mass.

The science of measurements, dimensions and weights. The determination and control of dimensions and weights is a sovereign right normally exercised by today's state institutes.

Lower limit of a weighing range on a legally verified instrument. ​The value of a load below which the weighing results may be subject to an excessive relative error. ​A weighing instrument may not be used below its minimum capacity. ​

If the weight falls below this value, then this can cause weighing results with a relative measurement deviation, which is too high. According to packaging control regulations, the minimum load depends on the verification scale interval. In other verifiable applications, it can also depend on the permitted imprecision.

The number of components in a modern weigh cell is kept as low as possible to reduce nonlinear effects and increase the precision and reproducibility of high-resolution weigh cells (e.g. EMC weigh cells). The consistent implementation of this principle can be seen in our monolithic weigh cells whose measuring system only consists of one single, high precision manufactured part.

Built-in, semi- or fully automatic mechanism for calibration/adjustment of the balance for high accuracy. Because of the high accuracy of this internal method, a built-in,  motorized calibration weight is preferable to an external weight.

Mounting kits minimize external force impacts on the load cells

Weighing instrument that has two or more weighing ranges, which differ in their maximum capacity and scale interval. ​Each range extends from zero to its individual maximum capacity. ​

Weight of a product after deducting the weight of its packaging and/or transport container

Newton (N) is the Unit of force. 1 N = 1 kg . 1m/sec²​

The most important parameter is the permissible maximum load without exceeding the specified error limits. It is typically composed of a preload, e.g. the load plate, and the measuring range.

A non-automatic weighing instrument (scale) requires the intervention of an operator, e.g. to place the load on the scale and to obtain the weighing result.

Describes the deviation of a load cell from theoretical linear correlation of the load and display. Non-Linearity can be measured after zero setting and calibration at max. load by applying several different loads.

• Organisation Internationale de Métrologie Légale also called "International Organization of Legal Metrology", regulates the metrological concerns in legal metrology. 
• The OIML provides recommendations for weighing technology that are recognized in many countries and also reflected in national standards. ​

Change in the value displayed when a given load is placed in different positions on the weighing pan

A locking device which prevents weighing above the maximum capacity of a scale or which protects components from overloading and damage.​

The “permeability” of a material in metal detection identifies the ability of the material to be magnetised. A metal with a high permeability allows the eddy current to flow through the metal easier than through air due to its low resistance. Other materials, on the other hand, behave in the opposite way and obstruct the eddy current in comparison to air due to a high resistance. As these have different effects on the detector coils, in this case a differentiation must be made between magnetic and nonmagnetic metals.

Describes the maximum distance (in mm) of the loading force to the central measuring axis of the load cell. If the load is outside these limits, the measurement result might not be correct.

Abbreviation for parts per million

In the case of automatic checkweighers, which sort objects according to several weight classes, the range of uncertainty within which the checkweigher is unable to allocate an object to a specific weight class.

Smallest difference that can still be read on a balance/scale. For balances with a scale indicating device (analogic), the readability is equal to the smallest fraction of a scale interval that can still be estimated with reasonable reliability or which can be determined by an auxiliary device.​ For balances and scales with a numeric indicator (digital display), the readability is equal to one digital step.  

The ability of a weighing instrument/scale to display corresponding results under constant testing conditions, when the same load is repeatedly placed onto the weighing pan in the same manner. ​In general, the difference between the largest and the smallest result is used to specify this quantity. ​

A term that has not yet been precisely standardized - It is commonly used for the quotient of the maximum capacity and the readability (“a resolution of 10000 steps or digits”), or for the readability (“a resolution of 0.1 g”). E.g., an industrial scale with 300 kg maximum capacity and 10 g readability has a resolution of 30,000 digits.​

Retail scales check (automatically) lumpy weighing products that are thus not of the same weight, but rather have different packaging weights due to their composition (e.g. pieces of fruit). The products are weighed in transition; the packaging price is calculated with the stored price per kilo and then transferred to, for example, a labeling machine that produces a corresponding label for the package.

Measuring device that determines the mass of a body based on the effect gravity has on that body. Depending on the functional process, the scale is classified as either automatic or non-automatic.

For weighing instruments with an analog indicator: ​The difference between the values, corresponding to two consecutive scale marks. ​For instruments with a digital display, this is the smallest digital step; i.e., the difference between any two consecutive indicated values. ​

Change in the displayed value divided by the load on the weighing instrument, which causes this change. ​For a correctly adjusted weighing instrument with a digital display, the sensitivity must always be exactly 1.0g/g=1.0. ​For a scale with an analog indicator, the sensitivity can also be indicated in scale divisions/g or mm/g.

Change in result due to temperature changes in the weighing system. ​These values are available from the data sheets (tolerance list).​ The Minebea Intec isoCal or isoTest function monitors this and corrects by adjustment automatically.

Deviation of sensitivity from true value 

Automatic checkweigher for single weighing that divides products of different mass into several classes of which each is indicated by it’s own weight range.

Difference between the indication of a weight at the instruments maximum capacity and the indication at zero load.

Speed Range of selected system according to datasheet. The speed of the checkweigher must be within the displayed range.

• For mechanical balances / scales: ​The mechanical system has stopped moving.  ​
• For Electronic balances / scales: Two or three consecutive readouts do not deviate by more than the limits of the previously selected stability range.

In electronic balances / scales: ​An electronic circuit or program for monitoring whether a readout is still changing. ​The severity of this control can be pre-adjusted by selecting the stability range. ​Some balances additionally allow a delay time to be set. ​

The time between complete placement of an object on the pan and display of the result. ​It can be influenced by setting the appropriate digital filter parameters.

Material measure, measuring instrument, reference material or measuring system intended to define, realize, conserve or reproduce a unit. ​In weighing technology, these are primarily weights that are used as mass standards. The standards with the highest accuracy are called primary standards or prototypes.

The idea of statistical process control is to produce and ensure consistent product quality. The statistical process control (SPC) of industrial production processes is continuous monitoring in support of consistent product quality. This is made possible through continuous recording of all key figures relevant to product quality within repeating, complex processes. Statistical process control provides the basic data for identifying weak points, or in other words what is needed for continuous improvement of the respective production processes. In this case, it is possible to monitor both quantitative and qualitative features of a product or process. If deviations outside of the defined target, trend or sample are identified, then a calibration can be carried out within the process. A production process controlled with SPC therefore allows for

• consistent product quality thanks to consistent processes as part of defined test routines
• more targeted planning of the tolerance specifications and therefore an increase in efficiency
• the documentation of product quality as evidence of conformity with regulations
• early intervention into the process in the event of initial indications of a possible error (error prevention)
• also statistical quality control

The weight of the product packaging

Zeroing the display when a weighing instrument is loaded. ​This allows the weight readout of an empty container to be reset to zero and the net weight to be read after filling the container.  ​A subtractive taring device reduces the available weighing capacity by the tare value; an additive taring device does not.

Range within which the display component of a scale can be "zeroed" by using the Tare Setting.

Temperature has an effect of the zero point and slope of a scale. In order to minimize these effects, each load cell is measured at different temperatures after production. The measured temperature effect is compensated either by manipulating the load cell directly in case of strain gauge cells, or by calculating temperature compensation factors which are stored in the weigh cell electronics and later applied to the weighing signal.

Range within which the scale (or other devices) may be operated.

The change of a measured value, (e.g. zero point or sensitivity) when the temperature changes, divided by the degree of temperature change.

A device or measure that either reduces or eliminates the influence of a change in temperature on mechanical and/ or electronic systems. A temperature compensating device can consist of a temperature sensor that influences an analog value (analog temperature compensation) or whose signal is digitized and used by the microprocessor to calculate a value by taking this temperature compensation value into account (this is known as digital temperature compensation)

Specification of the quantity of products per unit of time that can be inspected using an automatic checkweigher (e.g. 300 units/min). Throughput is a basis parameter for setting up automatic checkweighers because it is used to calculate several important parameters such as belt speed.  

In the idle state, the total receiver voltage is ideally zero and changes if magnetic or electrically conductive objects are guided through the detector coil.

The property of a result of measurement whereby this result must be related to a national or international standard, through an unbroken chain of documented comparisons.

In dynamic weighing, the transient time is the time during which a product is situated entirely on the weighing table. During this time, the measurement takes place, and therefore with lower transient time it is increasingly difficult to measure the product weight with sufficient accuracy. The transient time depends on the table length, product length and belt speed and is therefore directly connected to the throughput. It is calculated as (CC conveyor distance (mm) + roller diameter (mm) - length of product (mm)) / (belt speed (m/s))

Equipment for protecting sensitive parts of the measuring system on transport, particularly the weigh cell.

• The type-approval certificate documents the verifiability of a scale. In order to achieve a type-approval certificate, the scale has to be tested by a federal agency (generally a metrological state institute, e.g. the PTB). This includes both metrological as well as device specific requirements.
• The type-approval certificate for non-automatic scales is documented by the IEC type-approval certificate. The IEC type-approval certificate is valid for all member states of the European Union (EU).

The uncertainty of measurement “u” specifies the range for a measured value, within which the unknown, error-free result lies, usually with a statistical certainty of 95%. ​

The term "validus" is of Latin origin and means "effective". In order to control hazards related to food, monitoring measures are implemented along the entire food chain from primary production to processing to consumption. In this context, validation of the control measures (e.g. CCP, CP) is of great importance: validation provides evidence that the control measure or interaction of control measures selected for a particular hazard or risk is capable of controlling that particular hazard

Weighing instruments with readouts in partial weighing ranges; for example 60g readable to 0.1 mg; between 60g and 120g, to 0.2mg; and between 120g and 200g, to 0.5mg. ​The variable scale interval depends on the net weight displayed. ​After taring, the display will start with the smallest scale interval. ​Also called „multi-interval“ or „Polyrange“ instruments.

A measuring device like a scale is considered verifiable when its type is approved for verification. See ”verification”

Weighing instrument whose type has been tested for conformity and accepted for verification by the approval authorities (“notified body” in the EU).​

Verification comprises the metrological tests to be performed in accordance with the legal verification requirements and subsequent marking (stamping). ​The marking certifies that the weighing instrument, at the time of testing, met the legal verification requirements. ​Verification is carried out by the local verification officer who is responsible for metrological testing and approval. ​Since 1993, verification of a weighing instrument  for use as a legal measuring instrument can also be obtained through manufacturers with an approved quality assurance system.  

The Verification Act (Weights and Measures Act) serves as legal basis for measuring, measurement accuracy and consumer protection with regard to measurements. It regulates, among others, the legal metrology of commercial measuring devices like systems for Finished Packaging Control.

A scale division expressed in legal mass units (mg, g, kg, ct). ​This division is used for classification of balances and scales and refers to the permissible tolerances.

The time span from switching on the instrument on to the moment at which the instrument is capable of providing the accuracy indicated on its specifications sheet

• Load cell that is designed to convert the weight into a mass-dependent electrical signal. Two sensor principles are primarily used in modern electromechanical scales: Scales with Strain Gauges (SG) and scales that operate according to the principle of electromagnetic force compensation (EFC). 
• SG Weigh Cell: On SG weigh cells, strain gauges (SG) are applied to a deformation chassis. Strain gauges are electrical resistors that change their resistance according to their mechanical loads. These resistance changes are measured and evaluated. Thus, SG weigh cells principally require a deformation of the system body, thereby limiting the suitability of SG weigh cells for very fast weighing processes. 
• Weigh cells according to the electromagnetic force compensation principle generally can be considered to show higher performance. The achievable accuracy of a classic SG weigh cell is clearly below the achievable accuracy of a modern EMC weigh cell. The advantages of an SG weigh cell are its comparatively low manufacturing costs. 
• EMC Weigh Cell: The monolithic weighing system works with electromagnetic force compensation. The EMC weigh cell is used wherever an application places particularly high speed and/or accuracy requirements on the ACW. The significant advantages of the EMC weigh cell are its very high potential resolution, the large dead load range and the high speed, which is essentially achieved by the system displacement that directly acts upon the upcoming weight, therefore making an extremely fast response to the loaded condition possible

The term weighing electronics refers to products that evaluate signals from load cells or transmit or display measurement results/weight values from weighing instruments. With the help of the weighing electronics, the measurement results can be calibrated and, if necessary, re-calibrated (also known as adjustment).

Minebea Intec has a broad portfolio of weighing electronics which offer the optimum solution for every application. The range extends from simple weighing transmitters, which reliably process high-precision weight values from silo and hopper scales, to process and weighing indicators, which quickly and accurately display weight values, to weight controllers, which in addition to numerous interfaces and options can also offer the possibility of programming applications yourself. Weighing electronics are connected either directly or via cable junction boxes to load cells or a weighing platform. In addition, several scales can be connected to one weighing electronics device.

Read more "Weighing electronics"

In terms of metrology: ​Determination of errors of measurement (of a weighing instrument). ​In accordance with verification requirements, weights used to test the weighing performance of an instrument may not deviate by more than 1/3 from the maximum permissible errors of this instrument. ​

Weight counting scales automatically check lumpy weighing products with differing packaging weights, e.g. books, for the logistics department. However, instead of transferring a price, they transfer weight information to a labeling machine, or similar devices, in order to label the package.

An X-ray inspection system can be used to identify a number of physical foreign bodies such as metals, glass, rubber, stones and even certain types of plastics. The process of generating an X-ray image does not leave any traces behind on the product. For this reason, this method is preferred for use with packaged finished products, especially products in bottles, cans, glasses and bags.

An X-ray inspection system consists of the three core components – the generator, detector and image processor – and the mechanical and conveyor systems. Special hardware configurations are available for different application areas, which allow the core components to be used in a wide range of applications.

Influencing factors on X-ray inspection systems 

• Product dimensions and density
• Atomic mass
• Homogeneity of the product
• Different angle of view for optimal detection of foreign bodies
• Foreign body orientation
• Foreign body position

Reference state of a scale in an unloaded state => Scale display = 0 g (mg, kg, t, ...) 

Ability of a scale to maintain a stable Zero Point even while being influenced by external effects such as changing temperatures or moisture. The permissible zero point error caused by these kinds of influences on verifiable scales is regulated by law.

The range in which the scale can be zeroed. A selection of 1.9% means that the scale will zero off any weight within + or − 1.9% of the calibrated zero point.

Device for zeroing the digital display or analog indicator when the weighing pan is unloaded. ​On laboratory balances, the zero-setting key function is usually implemented in the tare key.

Device for maintaining the zero readout of a weighing instrument, within certain limits, automatically. ​The unofficial term is “auto zero” or “auto-taring”. ​Generally, on laboratory balances, zero tracking is performed even when the balance is tared while a load is on the weighing pan. ​As a rule, zero tracking can be turned off for certain applications (e.g. for measuring the smallest quantities added or for measuring evaporation from zero).