FAQ

ELECTRONIC SCALES FUNDAMENTALS
  • What is Zero value after power on?
    It is zero value that records after the digits countdown from 9 to 0.
  • What is Zero value after calibrate?
    It is zero value that records when doing specification calibration or weight calibration.
  • What is the zero range after press zero key?
    ± 2% of the maximum capacity
  • What is Span Drift?
    Temperature change effect on output
    Express way:
    TEMP. Effect on output: 0.020% R.O/10℃
    R.O is Rated Output
    For example:
    15.000kg*0.005kg Its external resolution =15.000kg/0.005kg= 3000E
    Change range of temperature:-10℃~ +40℃; temperature change in total:50℃
    3000E * 0.02% * (50℃/10℃) = 3E = 3 *0.005kg=0.015kg
    When using 1/3 capacity (equals to5.000kg) to measure:
    (5.000kg / 15.000kg) * 3000E * ( 50℃ / 10℃ ) = 1E = 0.005kg
  • What is re-linearity?
    It is also called repetitiveness. Methods of testing:
    We test 3 times through testing linearity. The largest tolerance with standard value in testing.
    Express way
    tolerance of re-linearity < 0.0333333 % R.O
    R.O is Rated Output
    For example:
    15.000kg*0.005kg Its external resolution =15.000kg/0.005kg= 3000E
    To shift tolerance of re-linearity of external value= 3000E * 0.0333333% = 0.999999E ≒ 1E =0.005kg
    Capacity: 0.000kg ~ 15.000kg; tolerance of linearity: ± 0.005kg
  • What is linearity?
    It is the largest tolerance with standard value in testing. Usually, we represent the tolerance of Nonlinearity for linearity Express way: tolerance of Nonlinearity < 0.0333333 % R.O
    R.O: Rated Output
    For example:
    15.000kg*0.005kg Its external resolution =15.000kg/0.005kg= 3000E
    To shift tolerance of nonlinearity of external value= 3000E * 0.0333333% = 0.999999E ≒ 1E =0.005kg
    Capacity: 0.000kg ~ 15.000kg; tolerance of nonlinearity: ± 0.005kg
  • What is unit weight insufficient?
    In counting mode, the unit weight of sampling or the unit weight you input is less than 0.2E, the icon of unit weight insufficient
  • What “OL,E1,E2,E4,E6,E7” stands for?
    【price computing scale】
    O L The weight value is over 9 division of maximum capacity.
    E 1 Zero value above 10% full scale.
    E 2 Zero value below 10% full scale.
    E 6 The internal value is over 350,000.
    E 7 The internal value is below 80,000.

    【counting scale】
    E 1 Zero value is too high (OIML or NTEP > 10% full scale)
    E 2 Zero value is low (OIML or NTEP < 10% full scale)
    E 6 Internal value is more than 700000(use in factory calibration)
    E 7 Internal value is lower than 100000(use in factory calibration)
    O L The weight value is over 9d of the maximum capacity. (d=division)
    U N S T A B L E Internal value is unstable
    Unstable time is over 10 seconds after pressing ZERO or TARE key

    【Weighing Scale】
    O L The weight value is over 9 division of maximum capacity.
    E 1 Zero value after power on is over +10% FS.
    E 2 Zero value after power on is less than -10% FS.
    E 4 Unstable zero return, unstable over 10 sec. Press zero key to leave E4.
    E 6 Zero is too high when calibrating. (over internal value350,000)
    E 7 Zero is too low when calibrating. (under internal value 80,000)
    E 1 0 The scale is not in level status.(only available with level detector equipment.)
    - - - - - - If the negative weight is over 20 divisions and there is no T or PT, the display shows “- - - - - -”
  • What is auto unit weight averaging?
    It is the unit weight which calculates quantities. It will modify the current weight automatically with adding quantities every time.
    The condition of averaging unit weight: the quantities you add every time are less than current quantities on the platter.
  • Gravity effects on weighbridge
    Gravity is the force that makes objects fall to the ground
    Acceleration of gravity at the Equator:GE=978.03184558cm/sec2
    Acceleration of gravity at the Poles:Gp=983.21772792cm/sec2

    If the G value of someplace is the acceleration of sth. fall to ground, G value is not decreasegradually from mantle to centre of the earth, but G value becomes the maximum in thebottom of mantle and then it decrease to zero gradually.


    The formula of G value in deferent latitude :
    Gψ=978.03185(1+0.005278895sin2ψ+0.000023462sin4ψ)
    G value in different places
    (1) Taipei:980cm/ sec2
    (2) German:981.1cm/ sec2
    (3) G value of Taipei/ G value of German:980/981.1=0.99887880949
    (4) Set weight *0.99887880949 as the weight you must set
    E.G. 1kg*0. 99887880949≒0.998kg you should input 998g and put 1kg to calibrate weigh
  • What is amplified factor value?
    The weight displays under the load. E.g. put 1,000g, read out 995g which is the amplified factor value.
  • What is capacity?
    The maximum value the scale can measure.
    The capacities of our products including: 150g、300g、500g、 600g、1200g、1500g、3000g、6kg、7.5kg、12kg、15kg、30kg、60 kg、120kg、150 kg、300 kg、600 kg、1t、1.5t、2t、3t、5t
  • What is division?
    The minimum value the scale can measure

    The divisions of our products including: 0.005g、0.01g、0.02g、0.05g、0.1g、0.2g、0.5g、1g、2g、5g、10g、20 g、50g、100g、200g、500g、1kg、2kg

  • What is resolution?
    Capacity / division (The maximum value / the minimum value)
    Example 1
    300g * 0.005 resolution= 300.000g/0.005g= 60000
    Example 2
    15kg * 0.001kg resolution= 15.000kg / 0.001kg = 15000
  • What is external resolution?
    The external analytical value of the scale
  • What is internal resolution?
    The internal analytical value of the scale the external value is convert by the internal analytical value. E.g. if the range of internal value is 0~400,000, the eternal value is 1/6,000, its internal resolution is 400,000/6000=66.
  • What is external value?
    The weight displays after weight calibration.
    The range of external value the minimum value ~ maximum value
  • What is weight calibration?
    Manual calibrate:Make the scale weight correctly through the adjustment from hardware Digits calibration:Make the scale weight correctly through the adjustment from software
  • What is linearity calibration?
    The linearity of load cell is lower than the resolution of the measurement so that we do multipule calibration to get close to the condition of non-linearity of load cell.
  • What is temperature calibration?
    Usually, the material will change when the temperature change. At this moment the weight will also change. It can decrease the tolerance through temperature calibration.
  • What is 9 OL?
    The maximum capacity adds n-tupling division to ensure the range of maximum capacity can be measured. Usually it is the maximum capacity + 9E, but it is the maximum capacity + 9E in Hong Kong and Brazil.
  • Common Units
    kg, g, T, lb, lb. oz, oz, twg, tl.T, MM(JPN), tl.J(HONG KONG JEWELY TAEL) tl.H(HONG KONG TAEL), ct, dr GN, ozt, dwt, t(INDIA)

OPERATION ISSUES
  • There are too many E2 and less E1 for internal value (only for MTW, CAW models)
    E 1 Internal value is too low
    E 2 Internal value is too high
    [Solutions]
    1. Please calibrate the internal value.
    First open the scale housing. On AD board , there are 2 VR: VR3 and VR 4. VR3 is used to calibrate weight and VR4 is used to calibrate internal value.
    For example: MTW300kg
    If E1 –08575 appears and it does not count down to zero after power on the scale, please adjust VR4 to -12450
    2. after adjust VR4, the display still shows -08455, and the internal value can not arrived -12450. Please shorten the resistance value of R29. If the internal value is -19995, please amplify the resistance value of R29.
    [Notes]
    Whether to change the factor resistance or resistance value of R29, please calibrate the weight and internal value again.
    How to see the internal value?
    Please press zero key and then press conformation key after power on the scale.
  • What to do, if the display shows E3? (Only for MTW, CAW models)
    1. Please press conformation key to enter into calibration mode, and do the calibration again.
    2. When enter into the calibration mode, the display shows E 3 which means the multiplying power is not enough (This phenomenon appears when exchange the Load Cell or change the specifications)
    For example
    When exchanging the Load Cell or changing the specifications, the display shows E 3 and the weight can not be calibrated. Please modify the multiplying power. E.g. put the full scale weight on the platter and displays 24000COUNT which means the multiplying power is too small.
    Please modify the resistance value of R11, R14, and R15 on AD board to change the count.
    24000COUNT 21000-27000
    30000COUNT 24000-30000
    If COUNT is in above rang, the display does not show E 3.
    36000COUNT is adjusted by weight. (Please adjust VR3)
  • The linearity of load cell is good or bad?
    Steps:
    1.please adjusts the avometer to DCV200 m. Open the housing of the scale, cut off the PIN4 and PIN5 of CN2 on AD board.
    2. Please connect PIN4 and PIN5 to avometer. Test the data when nothing on the scale and record④. Put weight (10 kg) on the scale and record the data①Œ. Put the second weight (20kgin total) on the scale and record the data②. Put the third weight (30kgin total) on the scale and record the data③Ž.
    Record the tolerance:③Ž-②,②-Œ①,①Œ-④
    Check whether the three tolerance < range of nonlinearity tolerance of L/C.
    Generally, the tolerance ≦ 0.0004mv/v
    For example: To test PW6KR~L/C
    0/3~output 0.254mv/5=0.0508mv
    1/3~output 3.508mv/5=0.7016mv
    2/3~output 6.7625mv/5=1.3525mv
    3/3~output 10.0155mv/5=2.0031mv
    1 ~ 2.0031mv-1.3525mv=0.6506mv
    2 ~1.3525mv-0.7016mv=0.6509mv
    3 ~0.7016mv-0.0508mv=0.6508mv
    4 ~0.6509mv(max)-0.6506mv(min)=0.0003mv
    5 ~0.0003mv < 0.0004mv ok
    Note: The voltage is divided by 5 because the standard specification of L/C is mv/v.
  • What to do if the scale is unstable and it can not do external calibration?
    For example:
    Scale: dual range, capacity:120kg Power on the scale and put20kgon the platter, the display shows20.12kg. It is useless to adjust VR3 of SPAN. Please shorten the resistance value of R11, R14 or R15 and then adjust the VR. (if the weight is not enough, please enlarge the resistance value)

    Whether to change the factor resistance or resistance value of R29, please calibrate the weight and internal value again.
  • The Zero point is unstable?
    1. Scale must be used under a stable temperature and stable air flow.
    2. If there is a windbreak, please use it.
  • Please note the following tips when using the scale.
    When you operate the scale following the manual, the following condition still appears. Please contact your supplier and do not purchase others components to exchange.
    1. the storage battery is damaged
    2. the charger is damaged
    3. You can not turn on the scale or the keypad is damaged.
    4. There is sth. Wrong with LCD
    5. No backlight
    6. the display shows error massage(except the error massage in the manual )
    7. the battery indication appears (the power is enough)
    8. zero point is unstable (except environment factors)
    9. The scale can not weight full scale. (protection screw is not dismantled)
    10. Wrong operation: Please refer to the manual If the scale is damaged, please contact your supplier or Excell precious company to ensure your rights and interests.
  • Some tips to maintain the scale
    1. Clean the scale Dust cover:
    use the wet cloth to clean the outer of the dust cover. Please do not let the water enter into the hole of the scale. No dust cover: please cover other dust cover. If there is no suitable dust cover, please clean the housing of the scale with little cleaning oil. Please do not clean the panel with cleaning oil.

    2. Dust cover
    if the dust cover is damaged, please change a new one.
    3. charging
    The scale should be charged every 3 months to prevent failure of the internal rechargeable battery.
  • How to judge impedance output or input of Load cell
    Steps:
    1. Please adjusts the avometer to2k
    2. Open the housing of the scale, Cut off the PIN 1 and PIN 2 of CN2 on AD board
    3. to test PIN1 and PIN2 with avometer and impedance should be about 420Ω.Cut off the PIN4 and PIN5 of CN2. to test PIN4 and PIN5 with avometer and impedance should be about 350Ω. If the result is 700Ω, please change the Load cell.

    Note: How to connect the E+.E-.S+.S- of L/C to CN2 on AD board?
    different connecting ways for different L/C
    ‧ 世銓~(Red cable E+)( black cable, blue cable E-)( green cable S+)(white cable S-)
    ‧ NMB~( Red cable E+)( white cable E-)(green cable S+)( blue cable S-)
    ‧ HBM~( green cable E+)( black cable E-)( Red cable S+)( white cable S-)
    ‧ TEDEA~( blue cable E+)( black cable E-)( white cable S+)( Red cable S-)
    ※S+ and S- of CN2 connect the input impedance
    ※E+ and E- of CN2 connect the output impedance
  • How to test output voltage (mV) of L/C
    Cut off the PIN5 and PIN4 on AD board. Please adjust the avometer to DCV200 mand test PIN4 and PIN5 with avometer after power on the scale. The voltage should be in +2mV~-2mV. If the voltage is beyond the range, please change the load cell.

    When the voltage is beyond above voltage, the display shows OF, at this time please test the volt of PIN 10 of U1 7135. If it is within -2V~ 2.5V, please enlarge resistance value of R29.

    Example: if the display shows OF after power on the scale. Do not connect the load cell. Power on the scale again and test the volt of PIN 10 of U1 7135. The volt is -2.2V, resistance value of R29 is 4.53K. Please enlarge the resistance value as 20K, test the volt of PIN 10 of U1 7135 as -1.53V and then adjust VR.

    Note: the resistance value of R29 should less then 50K. If the display still shows OF after change the resistance value of R29, please change the Load cell
  • Is the Insulation resistance in good condition?
    Please adjust the avometer to DCV 20 m. cut off the 4 cable on L/C. please touch one stick of avometer to the platter and touch another stick to one of the 4 cable. The avometer displays 1(normal). If displays other number, the Insulation resistance is too small. Please change the Load cell. (All the 4 cable should be tested)
  • How to do L/C compensation?
    When the zero voltage of L/C is less then 2mv/5v, it can do L/C compensation. Please adjust output of S+ and S- to the balance condition.

    Example: the output volt of L/C: S+2.50mv S- 2.42mv The tolerance of S+ and S- is 0.68mv. At this time S- 2.42mv need do L/C compensation這compensation way is as following: connecting changeable resistance to E+ and S- E+5v E-G S+2.50mv S- 2.42mv when it adjust S- to 2.50mv and S+ to 2.50mv, and test changeable resistance and record. Then record fixed resistance value of E+ S-. E+5v E-G S+2.50mv S-2.50mv
  • Please refer to the manual to install the product.
    If you have any questions, please contact us. Our technicians will replay your questions.

CERTIFICATIONS
  • What is ISO9001?
    ISO9001
    The ISO 9000 family addresses various aspects of quality management and contains some of ISO's best known standards. The standards provide guidance and tools for companies and organizations who want to ensure that their products and services consistently meet customer's requirements, and that quality is consistently improved. ISO 9001:2015 sets out the criteria for a quality management system and is the only standard in the family that can be certified to (although this is not a requirement). It can be used by any organization, large or small, regardless of its field of activity. In fact, there are over one million companies and organizations in over 170 countries certified to ISO 9001. This standard is based on a number of quality management principles including a strong customer focus, the motivation and implication of top management, the process approach and continual improvement. These principles are explained in more detail in the pdf Quality Management Principles. Using ISO 9001:2015 helps ensure that customers get consistent, good quality products and services, which in turn brings many business benefits.
  • What is CE Marking?
    CE

    CE is abbreviation of COMMUNAUTES EUROPEENNES. It tells clients the products is up to the request of safety, health even environment. According to the requirements of European board of administration, all products sale in European need CE marking on products.

    The science, culture and behavior in every country reflect on its industry standard and laws. Every European country has its own law system, including laws, regulations and non-governmental standard and so on, because of the differences between countries. These strict and complex requirements become trading obstacle. Related units draw up new method of technical standard and program to solve the trading obstacle. According to 100 item b in EEC, All the target of European order must bring into laws. The aim of making these regulations is to establish the rules in health protection, safety and other respect in order to ensure people’s rights and interests. These called necessary rules. These rules are to ensure the products are healthy, do not destroy environment and do harm to clients. The products can be selling in other countries. Factories can prove the products are up to the standard of European order, through sticking CE mark on products. If it is allow that CE mark can be sticking on package or documents. CE mark is only to show the product is up to all related standard.

  • What is OIML?
    OIML
    The International Organization of Legal Metrology is an intergovernmental treaty organization which • develops model regulations, standards and related documents for use by legal metrology authorities and industry, • provides mutual recognition systems which reduce trade barriers and costs in a global market, • represents the interests of the legal metrology community within international organizations and forums concerned with metrology, standardization, testing, certification and accreditation, • promotes and facilitates the exchange of knowledge and competencies within the legal metrology community worldwide, • cooperates with other metrology bodies to raise awareness of the contribution that a sound legal metrology infrastructure can make to a modern economy. The OIML issues several categories of publications: • International Recommendations, which are intended as model regulations for a number of categories of measuring instruments, and which OIML Member States are morally obliged to implement as far as possible; • International Documents, which are informative and are intended for guidance purposes; and • other publications such as Vocabularies, Guides, Basic Publications and Expert Reports. In addition, the OIML has developed the OIML Certification System (OIML-CS). Under the OIML-CS participants declare that they intend to accept and utilize OIML Certificates and/or OIML type evaluation reports from those participants that are entitled to issue OIML Certificates. The OIML is an “international standard-setting body” in the sense of the World Trade Organization's Technical Barriers to Trade Agreement. OIML publications should therefore be applied, when appropriate, by all signatories of the TBT Agreement when developing technical regulations, in application of Article 2.4 of that Agreement:
  • What is NTEP?
    NTEP
    NETP isabbreviation of National Type Evaluation Program. It is international standard procedure of test, inspection and comparison to check whether the scale is up to the weighing and measure standard(Handbook 44)of American. The weighing and measure standard(Handbook 44)of American is the standard that the office, government, factory, dealer and maintenance company obeyed. NTEP is made by NCWM(National Conference On Weights & Measures)and NIST(National Institute For Standards And Technology. It is issued in 1985/01/01 in United State.
  • What is RoHS?
    RoHS
    This document shall serve as formal declaration that product manufactuared by EXCELL are in compliance with the European Union RoSH Directive 2002/95/EC with respect to the following substance:
    Leab (Pb)
    Mercury (Hg)
    Cadmium (Cd)
    Hexavalent Chromium (Cr6+)
    Polybrominated biphenyls (PBB)
    Polybrominated biphenyls ethers (PBDE)

    We assure that any potential trace contamination levels of the substances are below the maximum level set by EU 2002/95/EC,or are exempt due to their application. Compliance is evidenced by written declaration/test report from our suppliers, assuring that materials we used in manufacturing process are Rosh compliant.

    We hereby declare that we’d full honor the contents of this contract. In case of breach & failure of this warranty contents, we declare that we’d take full responsibility for the substantial& related damage.

WHAT TO WATCH BEFORE YOU BUY SCALES
  • Tips when selecting scale products

    1. Select a good brand with good reputation, and with R&D, Quality Management team.
    2. Look at the capacity and specification that meet your needs.
    3. Check its repeatibility. Just repeatly put the same object on the scale to see whether the weight is the same.
    4. Check its function: Power on the scale and check if the digits is clear. Press the platter with hands to check whether the weight has changed and then release the hands to check the digits return to zero. Check the correction and reliability of the keypad and combination keys according to the manual.
    5. Check appearance to see if the outer of the scale is smooth, color even, no rip and the display should is even, the digits are clear.

  • Guarantee of EXCELL Scale Products.
    1. All our price computing scale has type approval certification.
    2. "3000 millions liability insurance" are guaranteed for all our scales.
    3. One year service and support for our scale products.
  • Tips when selecting scale manufactures
    1. Make sure the scale manufacturers have licence to do measuring instrument business.
    2. Make sure the scale products are with measuring instrument type approval.
    3. The manual and LIMITED WARRANTY documents are included.
    4. Insurance certificate are included.

INTRODUCTION TO DIGITAL SCALES
When comparing scales it is important to remember that readability means resolution and displayed resolution is really the ratio of capacity to readability. Displayed resolution is a good criteria to use when evaluating scales in addition to sources of weighing errors, ease of use, and other factors. When looking at counting scales, internal resolution will be helpful in choosing the capacity that is best suited to your application as it can be an indicator of the lightest part that can be accurately counted. It is less useful in comparing counting scales of different makes, because manufacturers tend to define it differently. But one thing is quite clear, when using certain parts, counting scales with higher relative internal resolution will deliver higher counting accuracy for a given sample size.

The International Society of Weighing and Measurement (ISWM) offers the following definition of resolution:
RESOLUTION: The smallest change in mechanical input which produces a detectable change in the output signal.
The Scale Manufacturer's Association says, "resolution is the minimum change in the measured variable which produces response [in] the instrument." According to the complete Scaleman's Handbook of Metrology, "we can say that accuracy and resolution are independent concepts with completely different meanings; accuracy referring to a scales indication relative to a nominal weight value; resolution to the minimum effective (readable) weight change, one graduation or increment." The Instrument Society of America has defined resolution as "the least interval between two adjacent discrete details which can be distinguished, one from another."

Dictionaries provide a list of definitions, most of which are entirely unrelated to weighing, however this author has resolved to limit the following discussion to resolution only as it applies to scales.

Scale manufacturers use the term resolution to help describe the performance of the products that they make. They sometimes use it interchangeably with the term "readability". The Scaleman's Handbook speaks of a "minimum effective (readable) weight change, one graduation or increment." Readable here refers to the smallest weight increment presented to the display, and in today's electronic scales the display is almost always digital. However, readability or resolution is by itself insufficient for assessing differences in scales. A scale that has a capacity of 50 lb and is readable to 0.001 lb is considered a better performing scale than a scale that has a capacity of only 5 lb and a readability of 0.001 lb Although the smallest weight increment, or readability, is the same for both scales, it takes a more accurate scale to provide 0.001 lb readability when weighing loads up to 50 pounds than one that is limited to 5 pounds. This is because the larger load is being divided into more increments than the smaller load. There are 50,000 increments of 0.001 lb in the 50 lb capacity scale, and only 5,000 increments of 0.001 lb in the 5 lb capacity scale. To draw a distinction between the performance of two scales having the same readability, manufacturers specify the ratio of the capacity to readability, and call it "displayed resolution". For a scale with a capacity of 50 lb and a readability of 0.001 lb, the ratio is 50 / 0.001, or 50,000 / 1. For a scale with a capacity of 25 lb and a readability of 0.0005 lb, the ratio is 25 / 0.0005, or 50,000 / 1. For a scale with a capacity of 10,000g and a readability of 0.2 g, the ratio is again 50,000 / 1. Despite different capacities, readabilities and units of measures, these three scales have one thing in common, a displayed resolution of 50,000 / 1, often shortened to 1 part in 50,000, or abbreviated even further to 1 in 50,000. Displayed resolution is one measure of scale performance that can be reliably used to compare scales of varying capabilities.

The ISWM definition of resolution refers to a "detectable change in the output signal." In most scales the change is detected visually on the display and gives rise to readability, from which is derived "displayed resolution". Counting scale manufacturer's know that the circuits in their counting scales can detect even smaller changes in mechanical input than is presented to the display. Since counting scales are often required to count parts that weigh less than the readability of the scale that they are weighed upon, efforts to define just how light a part can be counted on a particular scale have given rise to the sometime confusing term "internal counting resolution," or "internal resolution." There is no unanimity among manufacturers when it comes to defining internal resolution. As such, internal resolution is a very poor basis for comparing different brands of scales. One useful way to define it would be to first define resolution in terms of parts. Borrowing from the ISWM definition, resolution pertaining to counting scales is:

"The weight of the lightest part placed on a scale weighing element which produces a detectable change in the output signal."

Using the digitally displayed count as a measure of the output signal, and considering the detection of a single part as a detectable change in the output signal, then resolution for counting purposes could then be defined as the weight of the lightest part that can be counted in increments of one part. The ratio of the scale's capacity to the weight of the lightest part that can be counted in increments of one part is then the "internal resolution." A 50 lb capacity scale that can count parts as light as 0.0001 lb one part at a time would then have an internal resolution of 50 / 0.0001, or 1 part in 500,000.

In theory, a scale buyer can determine the lightest part that can be reliably counted on any given counting scale by back calculating from the capacity of the scale and its rated internal resolution. This is important in selecting the appropriate capacity for a counting application. Knowing the lightest part that must be counted, the buyer can compare this weight with the ratio of published capacity to published internal resolution.
One would expect a 5000g capacity scale with an internal resolution of 1 part in 500,000 to be able to count parts a light as 0.01g (5000 / 500,000) 1 part at a time, a 12,500g scale should count parts that weigh 0.025g (12,500 / 500,000), a 25,000g scale should count parts as light as 0.05g, (25,000 / 500,000), etc. Knowing a scale's internal resolution should enable a buyer to make the optimal trade-off of capacity, based upon his/her heaviest bin of parts, and resolution, based upon the lightest part that is stocked. Keeping in mind that manufacturers define internal resolution differently, such comparisons are more practically done on an intra-brand, as opposed to an inter-brand basis.

When counting fairly uniform parts the limiting factor for accuracy is almost always the total sample weight. The larger the sample size, the greater the total sample weight, and the better the counting accuracy. With certain items, usually parts that are light relative to the scale's capacity, it becomes impractical to count out a sample by hand that is large enough to provide the accuracy needed. One solution is to use a scale with a high internal resolution. Scales with high internal resolution develop the same counting accuracy as other scales, but require a smaller sample weight to do it. The ability to resolve a much smaller change in mechanical input, i.e., a much lighter part, means that the total sample weight, and therefore the Average Part Weight (APW) computed with the total sample weight, will be less subject to digitizing errors than the APW's computed by scales with lower internal resolution. The APW is divided into the weight of the bulk load placed on the scale to determine the total count. The more accurate the APW, the higher the accuracy of the count. For example if the true average part weight for an item is 0.6714g, a 50,000g capacity scale that has low internal resolution (1 part in 100,000) might calculate the APW as 0.65g when a 10 part sample is used, internally resolving to 0.5g. A scale with five times better internal resolution (1 part in 500,000) would resolve to 0.1g and calculate the APW as 0.67g. The resulting count on the lower internal resolution scale will be 96.8% accurate, while the count on the higher resolution scale will be 99.8% accurate. Therefore, two scales with the same capacity, using the same sample size to count a particular part, can easily produce widely varying results based only upon differences in the internal resolution.

When comparing scales, it is important to remember that readability means resolution, and displayed resolution is really the ratio of capacity to readability. Displayed resolution is a good criteria to use when evaluating scales, in addition to sources of weighing errors, ease of use, and other factors. When looking at counting scales, internal resolution will be helpful in choosing the capacity that is best suited to your application, as it can be an indicator of the lightest part that can be accurately counted. It is less useful in comparing counting scales of different makes because manufacturers tend to define it differently. But one thing is quite clear; when using certain parts, counting scales with higher relative internal resolution will deliver higher counting accuracy for a given sample size.

History
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