F1SCHEDULE 1GAUTOMATIC WEIGHING INSTRUMENTS (MI-006) (Annex VIII to the Directive)
The relevant essential requirements of Schedule 1A, the specific requirements of this Schedule and the conformity assessment procedures listed in Chapter I of this Schedule, apply to automatic weighing instruments defined below, intended to determine the mass of a body by using the action of gravity on that body.
DEFINITIONS
Automatic weighing instrument | An instrument that determines the mass of a product without the intervention of an operator and follows a predetermined programme of automatic processes characteristic of the instrument. |
Automatic catchweigher | An automatic weighing instrument that determines the mass of pre-assembled discrete loads (for example prepackages) or single loads of loose material. |
Weight labeller | An automatic catchweigher that labels individual articles with the weight value. |
Weight/price labeller | An automatic catchweigher that labels individual articles with the weight value, and price information. |
Automatic gravimetric filling instrument | An automatic weighing instrument that fills containers with a predetermined and virtually constant mass of product from bulk. |
Discontinuous totaliser (totalising hopper weigher) | An automatic weighing instrument that determines the mass of a bulk product by dividing it into discrete loads. The mass of each discrete load is determined in sequence and summed. Each discrete load is then delivered to bulk. |
Continuous totaliser | An automatic weighing instrument that continuously determines the mass of a bulk product on a conveyor belt, without systematic subdivision of the product and without interrupting the movement of the conveyor belt. |
Rail-weighbridge | An automatic weighing instrument having a load receptor inclusive of rails for conveying railway vehicles. |
SPECIFIC REQUIREMENTS
CHAPTER IRequirements common to all types of automatic weighing instruments
Rated Operating Conditions
1.
The manufacturer shall specify the rated operating conditions for the instrument as follows:
1.1.
For the measurand:
The measuring range in terms of its maximum and minimum capacity.
1.2.
For the electrical supply influence quantities:
In case of AC voltage supply | : | the nominal AC voltage supply, or the AC voltage limits. |
In case of DC voltage supply | : | the nominal and minimum DC voltage supply, or the DC voltage limits. |
1.3.
For the mechanical and climatic influence quantities:
The minimum temperature range is 30 °C unless specified otherwise in the following chapters of this Schedule.
The mechanical environment classes according to Schedule 1A, paragraph 1.3.2 are not applicable. For instruments which are used under special mechanical strain, e.g. instruments incorporated into vehicles, the manufacturer shall define the mechanical conditions of use.
1.4
For other influence quantities (if applicable):
The rate(s) of operation.
The characteristics of the product(s) to be weighed.
2.
Permissible effect of disturbances — Electromagnetic environment
The required performance and the critical change value are given in the relevant Chapter of this Schedule for each type of instrument.
Suitability
3.
3.1.
Means shall be provided to limit the effects of tilt, loading and rate of operation such that maximum permissible errors (MPEs) are not exceeded in normal operation.
3.2.
Adequate material handling facilities shall be provided to enable the instrument to respect the MPEs during normal operation.
3.3.
Any operator control interface shall be clear and effective.
3.4.
The integrity of the display (where present) shall be verifiable by the operator.
3.5.
Adequate zero setting capability shall be provided to enable the instrument to respect the MPEs during normal operation.
3.6.
Any result outside the measurement range shall be identified as such, where a printout is possible.
Conformity assessment
4.
The conformity assessment procedures specified in the modules in Schedule 1B applicable to automatic weighing instruments that the manufacturer can choose between are:
(a)
For mechanical systems:
(i)
B and D;
(ii)
B and E;
(iii)
B and F;
(iv)
D1;
(v)
F1;
(vi)
G; or
(vii)
H1.
(b)
For electromechanical instruments:
(i)
B and D;
(ii)
B and E;
(iii)
B and F;
(iv)
G; or
(v)
H1.
(c)
For electronic systems or systems containing software:
(i)
B and D;
(ii)
B and F;
(iii)
G; or
(iv)
H1.
CHAPTER IIAutomatic Catchweighers
1.
These categories are divided into four accuracy classes:
Y(I), Y(II), Y(a) & Y(b)
which shall be specified by the manufacturer.
MPE
2.
2.1.
MPE Category Y instruments
Net Load (m) in verification scale intervals (e) | Maximum permissible mean error | Maximum permissible error | |||
|---|---|---|---|---|---|
Y(I) | Y(II) | Y(a) | Y(b) | Static | Automatic |
0 < m ≤ 50,000 | 0 < m ≤ 5,000 | 0 < m ≤ 500 | 0 < m ≤ 50 | ± 0.5 e | ± 1 e |
50,000 < m ≤ 200,000 | 5,000 < m ≤ 20,000 | 500 < m ≤ 2,000 | 50 < m ≤ 200 | ± 1.0 e | ± 1.5 e |
200,000 < m | 20,000 < m ≤ 100,000 | 2,000 < m ≤ 10,000 | 200 < m ≤ 1,000 | ± 1.5 | ± 2 e |
Verification scale interval — single interval instruments
2.2.
Accuracy classes | Verification scale interval | Number of verification scale intervalsn = Max/e | ||
|---|---|---|---|---|
Minimum | Maximum | |||
Minimum | Maximum | |||
XI | Y(I) | 0.001 g ≤ e | 50,000 | |
XII | Y(II) | 0.001 g ≤ e ≤ 0.05 g | 100 | 100,000 |
0.1 g ≤ e | 5,000 | 100,000 | ||
XIII | Y(a) | 0.1 g ≤ e ≤ 2 g | 100 | 10,000 |
5 g ≤ e | 500 | 10,000 | ||
XIIII | Y(b) | 5 g ≤ e | 100 | 1,000 |
Verification scale interval — multi-interval instruments
2.3.
Verification scale interval | Number of verification scale intervalsn = Max/e | ||
|---|---|---|---|
Minimum value1 n = Maxi /e(i+1) For i = r the corresponding column of Table 2 applies with e replaced by er. | Maximum value n = Maxi /ei | ||
Y(I) | 0.001 g ≤ ei | 50,000 | |
Y(II) | 0.001 g ≤ ei≤ 0.05 g | 5,000 | 100,000 |
0.1 g ≤ ei | 5,000 | 100,000 | |
Y(a) | 0.1 g ≤ ei | 500 | 10,000 |
Y(b) | 5 g ≤ ei | 50 | 1 000 |
1 For i = r the corresponding column of Table 2 applies with e replaced by er. | |||
Where:
i = 1, 2, … r
i = partial weighing range
r = total number of partial ranges
Measurement Range
3.
In specifying the measurement range for class Y instruments the manufacturer shall take account that the minimum capacity shall not be less than:
class Y(I) | : | 100 e |
class Y(II) | : | 20 e for 0.001 g ≤ e ≤ 0.05 g, and 50 e for 0.1 g ≤ e |
class Y(a) | : | 20 e |
class Y(b) | : | 10 e |
Scales used for grading, e.g. postal scales and garbage weighers | : | 5 e |
Dynamic Setting
4.
4.1.
The dynamic setting facility shall operate within a load range specified by the manufacturer.
4.2.
When fitted, a dynamic setting facility that compensates for the dynamic effects of the load in motion shall be inhibited from operating outside the load range, and shall be capable of being secured.
Performance Under Influence Factors And Electromagnetic Disturbances
5.
5.1.
The MPEs due to influence factors are:
5.1.1.
For category Y instruments
— For each load in automatic operation; as specified in Table 1,
— For static weighing in non-automatic operation; as specified in Table 1.
5.1.2.
The critical change value due to a disturbance is one verification scale interval.
5.2.
Temperature range:
— For class Y(I) the minimum range is 5 °C,
— For class Y(II) the minimum range is 15 °C.
CHAPTER IIIAutomatic Gravimetric Filling Instruments
Accuracy classes
1.
1.1.
The manufacturer shall specify both the reference accuracy class Ref(x) and the operational accuracy class(es) X(x).
1.2.
An instrument type is designated a reference accuracy class, Ref(x), corresponding to the best possible accuracy for instruments of the type. After installation, individual instruments are designated for one or more operational accuracy classes, X(x), having taken account of the specific products to be weighed. The class designation factor (x) shall be ≤ 2, and in the form 1 × 10k, 2 × 10k or 5 × 10k where k is a negative whole number or zero.
1.3.
The reference accuracy class, Ref(x) is applicable for static loads.
1.4.
For the operational accuracy class X(x), X is a regime relating accuracy to load weight and (x) is a multiplier for the limits of error specified for class X(1) in paragraph 2.2.
MPE
2.
Static weighing error
2.1.
2.1.1.
For static loads under rated operating conditions, the MPE for reference accuracy class Ref(x), shall be 0.312 of the maximum permissible deviation of each fill from the average; as specified in Table 5; multiplied by the class designation factor (x).
2.1.2.
For instruments where the fill may be made up from more than one load (e.g. cumulative or selective combination weighers) the MPE for static loads shall be the accuracy required for the fill as specified in paragraph 2.2 (i.e. not the sum of the maximum permissible deviation for the individual loads).
Deviation from average fill
2.2.
Value of the mass, m (g), of the fills | Maximum permissible deviation of each fill from the average for class X(1) |
|---|---|
m ≤ 50 | 7.2 % |
50 < m ≤ 100 | 3.6 g |
100 < m ≤ 200 | 3.6 % |
200 < m ≤ 300 | 7.2 g |
300 < m ≤ 500 | 2.4 % |
500 < m ≤ 1,000 | 12 g |
1,000 < m ≤ 10,000 | 1.2 % |
10,000 < m ≤ 15,000 | 120 g |
15,000 < m | 0.8 % |
Note:
The calculated deviation of each fill from the average may be adjusted to take account for the effect of material particle size.
Error relative to pre-set value (setting error)
2.3.
For instruments where it is possible to pre-set a fill weight; the maximum difference between the pre-set value and the average mass of the fills shall not exceed 0.312 of the maximum permissible deviation of each fill from the average, as specified in Table 4.
Performance Under Influence Factor And Electromagnetic Disturbance
3.
3.1.
The MPE due to influence factors shall be as specified in paragraph 2.1.
3.2.
The critical change value due to a disturbance is a change of the static weight indication equal to the MPE as specified in paragraph 2.1 calculated for the rated minimum fill, or a change that would give equivalent effect on the fill in the case of instruments where the fill consists of multiple loads. The calculated critical change value shall be rounded to the next higher scale interval (d).
3.3.
The manufacturer shall specify the value of the rated minimum fill.
CHAPTER IVDiscontinuous Totalisers
1.
Accuracy Classes
Instruments are divided into four accuracy classes as follows: 0.2; 0.5; 1; 2.
2.
MPEs
Accuracy class | MPE of totalised load |
|---|---|
0.2 | ± 0.10 % |
0.5 | ± 0.25 % |
1 | ± 0.50 % |
2 | ± 1.00 % |
Totalisation scale interval
3.
The totalisation scale interval (dt) shall be in the range: 0.01 % Max ≤ dt ≤ 0.2 % Max
Minimum Totalised Load (Σmin)
4.
The minimum totalised load (Σmin) shall be not less than the load at which the MPE is equal to the totalisation scale interval (dt) and not less than the minimum load as specified by the manufacturer.
Zero Setting
5.
Instruments that do not tare weigh after each discharge shall have a zero setting device. Automatic operation shall be inhibited if zero indication varies by:
— 1 dt on instruments with automatic zero setting device;
— 0.5 dt on instruments with a semi-automatic, or non-automatic, zero setting device
Operator Interface
6.
Operator adjustments and reset function shall be inhibited during automatic operation.
Printout
7.
On instruments equipped with a printing device, the reset of the total shall be inhibited until the total is printed. The printout of the total shall occur if automatic operation is interrupted.
Performance under influence factors and electromagnetic disturbances
8.
8.1.
The MPEs due to influence factors shall be as specified in Table 6.
Load (m) in totalisation scale intervals (dt) | MPE |
|---|---|
0 < m ≤ 500 | ± 0.5 dt |
500 < m ≤ 2,000 | ± 1.0 dt |
2,000 < m ≤ 10,000 | ± 1.5 dt |
8.2.
The critical change value due to a disturbance is one totalisation scale interval for any weight indication and any stored total.
CHAPTER V
Accuracy classes
1.
Instruments are divided into three accuracy classes as follows: 0.5; 1; 2.
Measurement Range
2.
2.1.
The manufacturer shall specify the measurement range, the ratio between the minimum net load on the weighing unit and the maximum capacity, and the minimum totalised load.
2.2.
The minimum totalised load Σmin shall not be less than
800 d for class 0.5,
400 d for class 1,
200 d for class 2.
Where d is the totalisation scale interval of the general totalisation device.
MPE
3.
Accuracy class | MPE for totalised load |
|---|---|
0.5 | ± 0.25 % |
1 | ± 0.5 % |
2 | ± 1.0 % |
Speed of the belt
4.
The speed of the belt shall be specified by the manufacturer. For single-speed beltweighers, and variable-speed beltweighers having a manual speed setting control, the speed shall not vary by more than 5 % of the nominal value. The product shall not have a different speed than the speed of the belt.
General Totalisation Device
5.
It shall not be possible to reset the general totalisation device to zero.
Performance under influence factors and electromagnetic disturbances
6.
6.1.
The MPE due to influence factor, for a load not less than the Σmin, shall be 0.7 times the appropriate value specified in Table 7, rounded to the nearest totalisation scale interval (d).
6.2.
The critical change value due to a disturbance shall be 0.7 times the appropriate value specified in Table 7, for a load equal to Σmin, for the designated class of the beltweigher; rounded up to the next higher totalisation scale interval (d).
CHAPTER VIAutomatic Rail Weighbridges
Accuracy classes
1.
Instruments are divided into four accuracy classes as follows: 0.2; 0.5; 1; 2.
MPE
2.
2.1.
The MPEs for weighing-in-motion of a single wagon or a total train are shown in Table 8.
Accuracy class | MPE |
|---|---|
0.2 | ± 0.1 % |
0.5 | ± 0.25 % |
1 | ± 0.5 % |
2 | ± 1.0 % |
2.2.
The MPEs for the weight of coupled or uncoupled wagons weighing-in-motion shall be one of the following values, whichever is the greatest:
— the value calculated according to Table 8, rounded to the nearest scale interval;
— the value calculated according to Table 8, rounded to the nearest scale interval for a weight equal to 35 % of the maximum wagon weight (as inscribed on the descriptive markings);
— one scale interval (d).
2.3.
The MPEs for the weight of train weighing-in-motion shall be one of the following values, whichever is the greatest:
— the value calculated according to Table 9, rounded to the nearest scale interval;
— the value calculated according to Table 9, for the weight of a single wagon equal to 35 % of the maximum wagon weight (as inscribed on the descriptive markings) multiplied by the number of reference wagons (not exceeding 10) in the train, and rounded to the nearest scale interval;
— one scale interval (d) for each wagon in the train, but not exceeding 10 d.
2.4.
When weighing coupled wagons; the errors of not more than 10 % of the weighing results taken from one or more passes of the train may exceed the appropriate MPE given in paragraph 2.2, but shall not exceed twice the MPE.
Scale interval (d)
3.
The relationship between the accuracy class and the scale interval shall be as specified in Table 9.
Accuracy class | Scale interval (d) |
|---|---|
0.2 | d ≤ 50 kg |
0.5 | d ≤ 100 kg |
1 | d ≤ 200 kg |
2 | d ≤ 500 kg |
Measurement range
4.
4.1.
The minimum capacity shall not be less than 1 t, and not greater than the value of the result of the minimum wagon weight divided by the number of partial weighings.
4.2.
The minimum wagon weight shall not be less than 50 d.
Performance under influence factor and electromagnetic disturbance
5.
5.1.
The MPE due to an influence factor shall be as specified in Table 10.
Load (m) in verification scale intervals (d) | MPE |
0 < m ≤ 500 | ± 0.5 d |
500 < m ≤ 2,000 | ± 1.0 d |
2,000 < m ≤ 10,000 | ± 1.5 d |
5.2.
The critical change value due to a disturbance is one scale interval.