Handbook 44 – 2022 2.22. Automatic Bulk Weighing Systems

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Table of Contents

Page

Section 2.22. Automatic Bulk Weighing Systems............................................................... 2-83

A. Application ...................................................................................................................................................2-83

A.1. General................................................................................................................................................2-83

A.2. Exceptions...........................................................................................................................................2-83

A.3. Additional Code Requirements...........................................................................................................2-83

S. Specifications................................................................................................................................................2-83

S.1. Design of Indicating and Recording Elements and Recorded Representations. .................................2-83

S.1.1. Zero Indication......................................................................................................................2-83

S.1.2. Value of Scale Division (d). ..................................................................................................2-83

S.1.3. Capacity Indication and Recorded Representation. ..............................................................2-83

S.1.4. Weighing Sequence. .............................................................................................................2-83

S.1.5. Recording Sequence..............................................................................................................2-84

S.1.6. Provision for Sealing Adjustable Components on Electronic Devices. ................................2-84

S.2. Design of Balance and Damping Mechanism.....................................................................................2-84

S.2.1. Zero-Load Adjustment..........................................................................................................2-84

S.2.2. Damping Means....................................................................................................................2-84

S.3. Interlocks and Gate Control................................................................................................................2-84

S.3.1. Gate Position.........................................................................................................................2-84

S.3.2. Interlocks. .............................................................................................................................2-84

S.3.3. Overfill Sensor......................................................................................................................2-85

S.4. Design of Weighing Elements. ...........................................................................................................2-85

S.4.1. Antifriction Means................................................................................................................2-85

S.4.2. Adjustable Components........................................................................................................2-85

S.4.3. Multiple Load-Receiving Elements. .....................................................................................2-85

S.4.4. Venting. ................................................................................................................................2-85

S.5. Marking Requirements........................................................................................................................2-85

S.5.1. Capacity and Value of the Scale Division.............................................................................2-85

S.5.2. Weighing Elements...............................................................................................................2-85

S.5.3. Temperature Limits...............................................................................................................2-85

S.5.4. Accuracy Class. ....................................................................................................................2-85

N. Notes..............................................................................................................................................................2-86

N.1. Testing Procedures..............................................................................................................................2-86

N.1.1. Test Weights. ........................................................................................................................2-86

N.1.2. Increasing-Load Test. ...........................................................................................................2-86

N.1.3. Decreasing-Load Test. ..........................................................................................................2-86

N.1.4. Zero-Balance or No-Load Reference Value Change Test.....................................................2-86

N.1.5. Discrimination Test...............................................................................................................2-86

N.2. Verification (Testing) Standards.........................................................................................................2-86

T. Tolerances.....................................................................................................................................................2-86

T.1. Tolerance Application.........................................................................................................................2-86

T.1.1. To Errors of Underregistration and Overregistration............................................................2-86

T.1.2. To Increasing-Load Tests. ....................................................................................................2-86

T.1.3. To Decreasing-Load Tests. ...................................................................................................2-87

T.1.4. To Tests Involving Digital Indications or Representations...................................................2-87

T.2. Minimum Tolerance Values................................................................................................................2-87

T.2.1. For Systems Used to Weigh Construction Materials. ...........................................................2-87
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T.3. Basic Tolerance Values.......................................................................................................................2-87

T.3.1. Acceptance Tolerance...........................................................................................................2-87

T.3.2. For Systems Used to Weigh Grain........................................................................................2-87

T.3.3. For All Other Systems. .........................................................................................................2-87

T.4. Time Dependence................................................................................................................................2-87

T.5. Repeatability. ......................................................................................................................................2-87

T.6. Discrimination, Digital Automatic Indicating Scales. ........................................................................2-87

T.7. Influence Factors. ...............................................................................................................................2-87

T.7.1. Temperature..........................................................................................................................2-88

T.7.2. Barometric Pressure. ............................................................................................................2-88

T.7.3. Electric Power Supply...........................................................................................................2-88

UR. User Requirements ......................................................................................................................................2-88

UR.1. Selection Requirements. .....................................................................................................................2-88

UR.1.1. For Systems used to Weigh Grain.........................................................................................2-88

UR.1.2. For Systems used to Weigh Commodities other than Grain. ................................................2-88

UR.2. Installation Requirements. ..................................................................................................................2-88

UR.2.1. Protection from Environmental Factors................................................................................2-88

UR.2.2. Foundation, Supports, and Clearance....................................................................................2-89

UR.3. Loading Requirements........................................................................................................................2-89

UR.3.1. For Systems Used to Weigh Grain........................................................................................2-89

UR.3.2. For Systems Used to Weigh Commodities Other than Grain................................................2-89

UR.4. System Modification...........................................................................................................................2-89
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Section 2.22. Automatic Bulk Weighing Systems1

A. Application

A.1. General. – This code applies to automatic bulk weighing systems, that is, weighing systems adapted to the 

automatic weighing of a commodity in successive drafts of predetermined amounts automatically recording the 

no-load and loaded weight values and accumulating the net weight of each draft.

(Amended 1987)

A.2. Exceptions. – This code does not apply to batching systems.

(Added 2018)

A.3. Additional Code Requirements. – In addition to the requirements of this code, Automatic Bulk Weighing 

Systems shall meet the requirements of Section 1.10. General Code.

S. Specifications

S.1. Design of Indicating and Recording Elements and Recorded Representations.

S.1.1. Zero Indication. – Provisions shall be made to indicate and record a no-load reference value and, if the 

no-load reference value is a zero-value indication, to indicate and record an out-of-balance condition on both 

sides of zero.

S.1.1.1. Digital Zero Indication. – A digital zero indication shall represent a balance condition that is 

within ± 1⁄2 the value of the scale division.

S.1.2. Value of Scale Division (d). – The value of the scale division (d), expressed in a unit of weight, shall be 

equal to:

(a) 1, 2, or 5; or

(b) a decimal multiple or submultiple of 1, 2, or 5; or

(c) a binary submultiple of a unit of weight.

Examples: Scale divisions may be 0.01, 0.02, or 0.05; 0.1, 0.2, or 0.5; 1, 2, or 5; 10, 20, or 50; or 1⁄2, 1⁄4, 1⁄8, 1

/16, etc.

[Nonretroactive as of January 1, 1986]

(Amended 1987)

S.1.3. Capacity Indication and Recorded Representation. – An indicating or recording element shall not 

indicate or record any values when the gross load is in excess of 105 % of the capacity of the system.

S.1.4. Weighing Sequence. – For systems used to receive (weigh in), the no-load reference value shall be 

determined and recorded only at the beginning of each weighing cycle. For systems used to deliver (weigh out), 

the no-load reference value shall be determined and recorded only after the gross load reference value for each 

weighing cycle has been indicated and recorded.

1 (Title amended 1986)
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S.1.5. Recording Sequence. – Provision shall be made so that all weight values are indicated until the 

completion of the recording of the indicated value.

S.1.6. Provision for Sealing Adjustable Components on Electronic Devices. – For devices and systems in 

which the configuration or calibration parameters can be changed by use of a removable digital storage device, 

security shall be provided for those parameters as specified in G-S.8.2. Devices and Systems Adjusted Using 

Removable Digital Storage Devices. For parameters adjusted using other means, provision shall be made for 

applying a security seal in a manner that requires the security seal to be broken before an adjustment can be made 

to any component affecting the performance of the device.

(Amended 2019)

S.2. Design of Balance and Damping Mechanism.

S.2.1. Zero-Load Adjustment. – The weighing system shall be equipped with manual or semiautomatic means 

by which the zero-load balance or no-load reference value indication may be adjusted. Automatic zero-tracking 

and automatic zero-setting mechanisms are prohibited.

(Amended 2010)

S.2.1.1. Manual. – A manual zero-load or no-load reference value setting mechanism shall be operable 

or accessible only by a tool outside of or entirely separate from this mechanism or enclosed in a cabinet.

S.2.1.2. Semiautomatic. – A semiautomatic zero-load or no-load reference value setting mechanism shall 

meet the provisions of S.2.1.1. or shall be operable only when:

(a) the indication is stable within ± 3 scale divisions; and

(b) cannot be operated during a weighing operation.

S.2.2. Damping Means. – A system shall be equipped with effective means necessary to bring the indications 

quickly to a readable, stable equilibrium. Effective means shall also be provided to permit the recording of weight 

values only when the indication is stable within plus or minus three scale divisions for devices with 10 000 scale 

divisions, or plus or minus one division for devices with less than 10 000 scale divisions.

S.3. Interlocks and Gate Control.

S.3.1. Gate Position. – Provision shall be made to clearly indicate to the operator the position of the gates 

leading directly to and from the weigh hopper.

S.3.2. Interlocks. – Each automatic bulk weighing system shall have operating interlocks to provide for the 

following:

(a) Product cannot be cycled and weighed if the weight recording element is disconnected or subjected to a 

power loss.

(b) The recording element cannot print a weight if either of the gates leading directly to or from the weigh 

hopper is open.

(c) A “low paper” sensor, when provided, is activated.

(d) The system will operate only in the proper sequence in all modes of operation.

(e) When an overfill alarm is activated, the system shall indicate and record an overfill condition.

(Amended 1993)
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S.3.3. Overfill Sensor.

(a) The weigh hopper shall be equipped with an overfill sensor which will cause the feed gate to close, 

activate an alarm, and inhibit weighing until the overfill condition has been corrected.

(Added 1993)

(b) If the system is equipped with a lower garner or surge bin, that garner shall also be equipped with an 

overfill sensor which will cause the gate of the weigh hopper to remain open, activate an alarm, and 

inhibit weighing until the overfill condition has been corrected.

[Nonretroactive as of January 1, 1998]

(Amended 1997)

S.4. Design of Weighing Elements.

S.4.1. Antifriction Means. – At all points at which a live part of the mechanism may come into contact with 

another part in the course of normal usage, frictional effects shall be reduced to a minimum by means of suitable 

antifriction means, opposing surfaces and points being properly shaped, finished, and hardened.

S.4.2. Adjustable Components. – An adjustable component, such as a potentiometer, shall be held securely 

in adjustment and, except for a component for adjusting level or a no-load reference value, shall not be adjustable

from the outside of the device.

S.4.3. Multiple Load-Receiving Elements. – A system with a single indicating or recording element, or a 

combination indicating recording element, that is coupled to two or more load-receiving elements with 

independent weighing systems, shall be provided with means to prohibit the activation of any load-receiving 

element (or elements) not in use, and shall be provided with automatic means to indicate clearly and definitely 

which load-receiving element (or elements) is in use.

S.4.4. Venting. – All weighing systems shall be vented so that any internal or external pressure will not affect 

the accuracy or operation of the system.

S.5. Marking Requirements. (Also see Section 1.10. General Code Paragraph G-S.1. Identification.)

S.5.1. Capacity and Value of the Scale Division. – The capacity of the weighing system and the value of the 

scale division shall be clearly and conspicuously marked on the indicating element near the weight value 

indications.

S.5.2. Weighing Elements. – On a weighing element not permanently attached to an indicating element, there 

shall be clearly and permanently marked for the purposes of identification, the name, initials, or trademark of the 

manufacturer, the manufacturer’s designation that positively identifies the pattern or design, and the nominal 

capacity.

S.5.3. Temperature Limits. – Unless the temperature range is − 10 °C to + 40 °C (14 °F to 104 °F), the 

temperature range shall be marked on the device.

[Nonretroactive as of January 1, 1986]

(Added 1985)

S.5.4. Accuracy Class.

(a) All systems used to weigh grain shall be marked Class III.*

(b) All other systems shall be marked either Class III or III L.*
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(*Also see Section 2.20. Scales Code for the parameters for these accuracy classes for scales. The specific 

requirements for automatic bulk weighing systems apply to these devices when there is a conflict between the 

Scales Code and the Automatic Bulk Weighing Systems Code.)

[Nonretroactive as of January 1, 1986]

(Added 1985) (Amended 1992)

N. Notes

N.1. Testing Procedures.

N.1.1. Test Weights. – The increasing load test shall be conducted using test weights equal to at least 10 % of 

the capacity of the system:

(a) on automatic grain bulk-weighing systems installed after January 1, 1984; and

(b) on other automatic bulk-weighing systems installed after January 1, 1986.

(Amended 1987)

N.1.2. Increasing-Load Test. – An increasing-load test consisting of substitution and strain-load tests shall be 

conducted up to the used capacity of the weighing system.

(Amended 1987)

N.1.3. Decreasing-Load Test. – A decreasing-load test shall be conducted on devices used to weigh out.

(Added 1986)

N.1.4. Zero-Balance or No-Load Reference Value Change Test. – A test for change of zero-balance or 

no-load reference value shall be conducted on all scales after the removal of any test load. The change shall not 

be more than the minimum tolerance applicable.

N.1.5. Discrimination Test. – A discrimination test shall be conducted on all automatic indicating scales with 

the weighing device in equilibrium at zero-load and at maximum test load, and under controlled conditions in 

which environmental factors are reduced to the extent that they will not affect the results obtained.

[Nonretroactive as of January 1, 1986]

N.1.5.1. Digital Device. – On a digital device, this test is conducted from just below the lower edge of the 

zone of uncertainty for increasing-load tests, or from just above the upper edge of the zone of uncertainty for 

decreasing-load tests.

(Added 1987)

N.2. Verification (Testing) Standards. – Standard weights and masses used in verifying weighing devices shall 

comply with requirements of NIST Handbook 105-1 (Class F) or the tolerances expressed in Appendix A, 

Fundamental Considerations, paragraph 3.2. (i.e., one-third of the smallest tolerance applied).

T. Tolerances

T.1. Tolerance Application. – Tolerance values shall be applied to all indications and recorded representations of 

a weighing system.

T.1.1. To Errors of Underregistration and Overregistration. – The tolerances hereinafter prescribed shall 

be applied equally to errors of underregistration and errors of overregistration.

T.1.2. To Increasing-Load Tests. – Basic tolerances shall be applied.
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T.1.3. To Decreasing-Load Tests. – Basic tolerances shall be applied to systems used to weigh out.

(Added 1986)

T.1.4. To Tests Involving Digital Indications or Representations. – To the tolerances that would otherwise 

be applied, there shall be added an amount equal to one-half the value of the scale division. This does not apply 

to digital indications or recorded representations that have been corrected for rounding using error weights.

(Added 1986)

T.2. Minimum Tolerance Values. – The minimum tolerance value shall not be less than half the value of the scale 

division.

T.2.1. For Systems Used to Weigh Construction Materials. – The minimum maintenance and acceptance 

tolerance shall be 0.1 % of the weighing capacity of the system, or the value of the scale division, whichever is 

less.

(Added 1986)

T.3. Basic Tolerance Values.

T.3.1. Acceptance Tolerance. – The basic acceptance tolerance shall be one-half the basic maintenance 

tolerance.

T.3.2. For Systems Used to Weigh Grain. – The basic maintenance tolerance shall be 0.1 % of test load.

T.3.3. For All Other Systems. – The basic maintenance tolerance shall be 0.2 % of test load.

(Amended 1986)

T.4. Time Dependence. – At constant test conditions, the indication 20 seconds after the application of a load and 

the indication after one hour shall not differ by more than the absolute value of the applicable tolerance for the applied 

load.

[Nonretroactive as of January 1, 1987]

(Added 1986)

T.5. Repeatability. – The results obtained by several weighings of the same load under reasonably static test 

conditions shall agree within the absolute value of the maintenance tolerance for that load, and shall be within 

applicable tolerances.

(Added 1986)

T.6. Discrimination, Digital Automatic Indicating Scales. – A test load equivalent to 1.4 d shall cause a change 

in the indicated or recorded value of at least 2.0 d. This requires the zone of uncertainty to be not greater than 0.3 times 

the value of the scale division.

(Added 1985)

T.7. Influence Factors. – The following factors are applicable to tests conducted under controlled conditions only, 

provided that:

(a) types of devices approved prior to January 1, 1986, and manufactured prior to January 1, 1988, need not 

meet the requirements of this section; and

(b) new types of devices submitted for approval after January 1, 1986, shall comply with the requirements of this 

section; and

(c) all devices manufactured after January 1, 1988, shall comply with the requirements of this section.

[Nonretroactive as of January 1, 1986]
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T.7.1. Temperature. – Devices shall satisfy the tolerance requirements under the following temperature 

conditions:

T.7.1.1. If not marked on the device, the temperature limits shall be: − 10 °C to 40 °C (14 °F to 104 °F).

T.7.1.2. If temperature limits are specified for the device, the range shall be at least 30 °C (54 °F).

T.7.1.3. Temperature Effect on Zero-Load Balance. – The zero-load indicator shall not vary by more 

than one division per 5 °C (9 °F) change in temperature.

T.7.1.4. Operating Temperature. – An indicating or recording element shall not display or record any 

usable values until the operating temperature necessary for accurate weighing and a stable zero-balance 

condition has been attained.

[Nonretroactive as of January 1, 1986]

T.7.2. Barometric Pressure. – The zero indication shall not vary by more than one scale division for a change 

in barometric pressure of 1 kPa over the total barometric range of 95 kPa to 105 kPa (28 in to 31 in of mercury).

[Nonretroactive as of January 1, 1986]

T.7.3. Electric Power Supply.

T.7.3.1. Power Supply, Voltage, and Frequency.

(a) Weighing devices that operate using alternating current must perform within the conditions defined 

in paragraphs T.2. through T.7., inclusive over the line voltage range of 100 V to 130 V or 200 V 

to 250 V rms as appropriate and over the frequency range of 59.5 Hz to 60.5 Hz.

(b) Battery-operated instruments shall not indicate nor record values outside the applicable tolerance 

limits when battery power output is excessive or deficient.

T.7.3.2. Power Interruption. – A power interruption shall not cause an indicating or recording element 

to display or record any values outside the applicable tolerance limits.

[Nonretroactive as of January 1, 1986]

(Added 1985)

UR. User Requirements

UR.1. Selection Requirements.

UR.1.1. For Systems used to Weigh Grain. – The number of scale divisions of a weighing system shall not be 

less than 2 000 nor greater than 10 000 divisions.

[Nonretroactive as of January 1, 1984]

(Amended 1986 and 1992)

UR.1.2. For Systems used to Weigh Commodities other than Grain. – The number of scale divisions shall not 

be less than 500 nor greater than 10 000.

[Nonretroactive as of January 1, 1987]

(Added 1986)

UR.2. Installation Requirements.

UR.2.1. Protection from Environmental Factors. – The indicating elements, the lever system or load cells, 

the load-receiving element, and any permanently installed test weights shall be adequately protected from 
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environmental factors such as wind, weather, and RFI that may adversely affect the operation or performance of 

the system.

UR.2.2. Foundation, Supports, and Clearance. – The foundation and supports of any system shall be such 

as to provide strength, rigidity, and permanence of all components, and clearance shall be provided around all 

live parts so that no contact can result before or during operation of the system.

UR.3. Loading Requirements.

UR.3.1. For Systems Used to Weigh Grain. – A system shall not be used to weigh drafts less than 40 % of 

the weighing capacity of the system except for a final partial draft. Loads shall not normally be retained on the 

weighing element for a period longer than a normal weighing cycle.

(Amended 1986)

UR.3.2. For Systems Used to Weigh Commodities Other than Grain. – A system shall not be used to weigh 

drafts less than 20 % of the weighing capacity of the system except for a final partial draft. Loads shall not 

normally be retained on the weighing element for a period longer than a normal weighing cycle.

[Nonretroactive as of January 1, 1987]

(Added 1986)

UR.4. System Modification. – The weighing system shall not be modified except when the modification has been 

approved by a competent engineering authority, preferably that of the engineering department of the manufacturer of 

the scale, and the official with statutory authority having jurisdiction over the scale.

(Amended 1991)
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