Scales used for trade settlement are classified as measuring instruments subject to compulsory verification by the state in accordance with the law. This includes crane scales, small bench scales, platform scales, and truck scale products. Any scale used for trade settlement must undergo compulsory verification; otherwise, penalties may be imposed. The verification is carried out in accordance with JJG 539-2016 Verification Regulation for Digital Indicating Scales, which can also be applied to the verification of truck scales. However, there is another verification regulation specifically for truck scales that may be referenced: JJG 1118-2015 Verification Regulation for Electronic Truck Scales (Load Cell Method). The choice between the two depends on the actual situation, although in most cases verification is performed in accordance with JJG 539-2016.
In JJG 539-2016, the description of scales is as follows:
In this Regulation, the term “scale” refers to a type of non-automatic weighing instrument (NAWI).
Principle: When a load is placed on the load receptor, the weighing sensor (load cell) generates an electrical signal. This signal is then converted and processed by a data processing device, and the weighing result is displayed by the indicating device.
Structure: The scale consists of a load receptor, a load cell, and a weighing indicator. It may be of an integral construction or a modular construction.
Application: These scales are primarily used for goods weighing and measurement, and are widely applied in commercial trade, ports, airports, warehousing and logistics, metallurgy, as well as in industrial enterprises.
Types of digital indicating scales: Electronic bench and platform scales (collectively referred to as electronic bench/platform scales), which include: Price-computing scales, Weighing-only scales, Barcode scales, Counting scales, Multi-division scales, Multi-interval scales and etc.; Electronic crane scales, which include: Hook scales, Hanging hook scales, Overhead traveling crane scales, Monorail scales and etc.; Fixed electronic scales, which include: Electronic pit scales, Electronic surface-mounted scales, Electronic hopper scales and etc.
There is no doubt that large weighing instruments such as pit scales or truck scales belong to the category of fixed electronic scales, and therefore can be verified in accordance with the Verification Regulation for Digital Indicating Scales (JJG 539-2016). For small-capacity scales, loading and unloading of standard weights is relatively easy. However, for large-scale scales measuring 3 × 18 meters or with capacities over 100 tons, operation becomes much more difficult. Strictly following the JJG 539 verification procedures poses significant challenges, and some requirements may be practically impossible to implement.For truck scales, the verification of metrological performance mainly includes five items: Zero-setting accuracy and tare accuracy, Eccentric load (off-center load), Weighing, Weighing after tare, Repeatability and discrimination range. Among these, eccentric load, weighing, weighing after tare, and repeatability are particularly time-consuming. If the procedures are strictly followed, it may be impossible to complete the verification of even a single truck scale within one day. Even when repeatability is good, allowing for a reduction in the amount of test weights and partial substitution, the process remains quite challenging.
7.1 Standard Instruments for Verification
7.1.1 Standard Weights
7.1.1.1 The standard weights used for verification shall comply with the metrological requirements specified in JG99, and their errors shall not exceed 1/3 of the maximum permissible error for the corresponding load as specified in Table 3.
7.1.1.2 The number of standard weights shall be sufficient to meet the verification requirements of the scale.
7.1.1.3 Additional standard weights shall be provided for use with the intermittent load point method to eliminate rounding errors.
7.1.2 Substitution of Standard Weights
When the scale is verified at its place of use, substitute loads (other masses
with stable and known weights) may be used to replace part of the standard
weights:
If the scale’s repeatability exceeds 0.3e, the mass of the standard weights used shall be at least 1/2 of the maximum scale capacity;
If the scale’s repeatability is greater than 0.2e but not more than 0.3e, the mass of the standard weights used may be reduced to 1/3 of the maximum scale capacity;
If the scale’s repeatability does not exceed 0.2e, the mass of the standard weights used may be reduced to 1/5 of the maximum scale capacity.
The repeatability mentioned above is determined by applying a load of approximately 1/2 of the maximum scale capacity (either standard weights or any other mass with stable weight) to the load receptor three times.
If the repeatability falls within 0.2e–0.3e / 10–15 kg, a total of 33 tons of standard weights is required. If the repeatability exceeds 15 kg, then 50 tons of weights are needed. It would be quite difficult for the verification institute to bring 50 tons of weights on-site for scale verification. If only 20 tons of weights are brought, it may be assumed that the repeatability of the 100-ton scale is defaulted to not exceeding 0.2e / 10 kg. Whether a 10 kg repeatability can actually be achieved is questionable, and everyone can have an idea of the practical challenges. Moreover, although the total amount of standard weights used is reduced, substitute loads must still be correspondingly increased, so the total test load remains unchanged.
1. Testing of Weighing Points
For weighing verification, at least five different load points should be selected. These should include the minimum scale capacity, the maximum scale capacity, and the load values corresponding to changes in the maximum permissible error, i.e., medium accuracy points: 500e and 2000e. For a 100-ton truck scale, where e = 50 kg, this corresponds to: 500e = 25 t, 2000e = 100 t. The 2000e point represents the maximum scale capacity, and testing it may be difficult in practice. Furthermore, weighing after tare requires repeating the verification at all five load points. Do not underestimate the workload involved in five monitoring points—the actual work of loading and unloading is quite substantial.
2. Eccentric Load Test
7.5.11.2 Eccentric Load and Area
a) For scales with more than 4 support points (N > 4): The load applied to each support point should be equivalent to 1/(N–1) of the maximum scale capacity. The weights should be applied successively above each support point, within an area approximately equal to 1/N of the load receptor. If two support points are too close, applying the test as described above may be difficult. In this case, double the load can be applied over an area twice the distance along the line connecting the two support points.
b) For scales with 4 or fewer support points (N ≤ 4): The applied load should be equivalent to 1/3 of the maximum scale capacity.
The weights should be applied successively within an area approximately equal to 1/4 of the load receptor, as shown in Figure 1 or a configuration approximately equivalent to Figure 1.
For a 100-ton truck scale measuring 3 × 18 meters, there are typically at least eight load cells. Dividing the total load evenly, 100 ÷ 7 ≈ 14.28 tons (approximately 14 tons) would need to be applied to each support point. It is extremely difficult to place 14 tons of weights on each support point. Even if the weights can be physically stacked, repeatedly loading and unloading such massive weights involves a substantial workload.
3. Verification Loading Method vs. Actual Operational Loading
From the perspective of loading methods, the verification of truck scales is similar to that of small-capacity scales. However, during on-site verification of truck scales, weights are typically hoisted and directly placed on the scale platform, similar to the procedure used during factory testing. This method of applying the load differs significantly from the actual operational loading of a truck scale. Direct placement of hoisted weights on the scale platform does not generate horizontal impact forces, does not engage the scale’s lateral or longitudinal stop devices, and makes it difficult to detect the effects of straight entry/exit lanes and longitudinal stop devices at both ends of the scale on weighing performance.
In practice, verification of metrological performance using this method does not fully reflect the performance under actual operating conditions. Verification based solely on this non-representative loading method is unlikely to detect the true metrological performance under real working conditions.
According to JJG 539-2016 Verification Regulation for Digital Indicating Scales, using standard weights or standard weights plus substitutes to verify large-capacity scales involves significant challenges, including: Large workload, High labor intensity, High transportation cost for weights, Long verification time, Safety risks and etc. These factors create considerable difficulties for on-site verification. In 2011, the Fujian Institute of Metrology undertook the national key scientific instrument development project Development and Application of High-Precision Load Measuring Instruments for Weighing Scales. The developed Weighing Scale Load Measuring Instrument is an independent auxiliary verification device compliant with OIML R76, enabling accurate, fast, and convenient verification of any load point, including full-scale, and other verification items for electronic truck scales. Based on this instrument, JJG 1118-2015 Verification Regulation for Electronic Truck Scales (Load Measuring Instrument Method) was officially implemented on November 24, 2015.
Both verification methods have their advantages and disadvantages, and the choice in practice should be made based on the actual situation.
Advantages and disadvantages of the two verification regulations:
JJG 539-2016 Advantages: 1. Uses standard loads or substitutes better than M2 class, allowing the verification division of electronic truck scales to reach 500–10,000. 2. Standard instruments have a verification cycle of one year, and traceability of standard instruments can be completed locally at municipal or county-level metrology institutes.
Disadvantages: Extremely large workload and high labor intensity; High cost of loading, unloading, and transporting weights; Low efficiency and poor safety performance; Long verification time; strict adherence may be difficult in practice.
JJG 1118 Advantages: 1. The Weighing Scale Load Measuring Instrument and its accessories can be transported to the site in a single two-axle vehicle. 2. Low labor intensity, low load transportation cost, high verification efficiency, good safety performance, and short verification time. 3. No need for unloading/reloading for verification.
Disadvantages: 1. Using the Electronic Truck Scale (Load Measuring Instrument Method), the verification division can only reach 500–3,000. 2. The electronic truck scale must install a reaction force device (cantilever beam) connected to the piers (either fixed concrete piers or movable steel structure piers). 3. For arbitration or official appraisal, verification must follow JJG 539 using standard weights as the reference instrument. 4. Standard instruments have a verification cycle of six months, and most provincial or municipal metrology institutes have not established traceability for these standard instruments; traceability must be obtained from qualified institutions.
JJG 1118-2015 adopts an independent auxiliary verification device recommended by OIML R76, and serves as a supplement to the verification method of electronic truck scales in JJG 539-1997. Applicable to electronic truck scales with a maximum capacity ≥ 30 t, verification division ≤ 3,000, at medium accuracy or ordinary accuracy levels. Not applicable to multi-division, multi-range, or electronic truck scales with extended indicating devices.
Post time: Aug-26-2025