GB/T 21296.5-2020Automatic instruments for weighing road vehicles in motion—Part 5: Crystal quartz type (English PDF)

5.8 Unit of measurement

The unit of measurement of mass and load of crystal quartz dynamic vehicle weighing instruments is kilogram (kg) or ton (t).

5.9 Operating speed

Within the nominal operating speed range, crystal quartz dynamic vehicle weighing instruments shall maintain the corresponding metering performance requirements and technical requirements. When it exceeds the operating speed range, no result will be output. Or according to the requirements of 9.3.8 in GB/T 21296.1-2020, a violation prompt will be given.

This operating speed range can be adjusted or determined according to the test situations during the field weighing test.

6.1 Overview

Quartz dynamic vehicle weighing instruments shall meet the requirements of 6.2~6.8 and the provisions of Clause 6 in GB/T 21296.1-2020.

6.2 General technical requirements

Quartz dynamic vehicle weighing instruments shall be designed and manufactured to […]

6.3.3 Insulation resistance

The impedance of crystal quartz sensor shall not be lower than 100 Gohm.

6.3.4 Anti-corrosion requirements

Crystal quartz sensors shall be effectively protected against corrosion and rust.

If a cladding or coating layer is designed on the surface, the cladding and coating layer shall be smooth and intact. The coating shall have high adhesion strength; shall be firm, uniform, and consistent in color. There shall be no defects such as spots and scratches.

6.3.5 Metal frame strength

The strength of metal frame shall meet the stability and reliability requirements of long-term continuous operation.

6.4 General technical requirements for charge amplifier

The electrical parameters and degree of protection of charge amplifier shall meet the requirements of the design and application of quartz dynamic vehicle weighing instruments. If necessary, according to the test method of JJG 338, test and detect its parameters such as nonlinear error, high-low pass cutoff frequency.

6.5 General technical requirements for weighing meter

The electrical parameters and degree of protection of weighing meter shall meet the requirements of the design and application of quartz dynamic vehicle weighing instruments; and comply with the relevant provisions of GB/T 7724.

6.6 Vehicle identification device

Quartz dynamic vehicle weighing instruments shall be equipped with vehicle identification devices, such as ground-sensing coil vehicle detector, infrared light curtain (grating), laser vehicle separator, etc. The devices shall be able to detect whether the vehicle is in the weigh zone.

6.7 Interface

Quartz dynamic vehicle weighing instruments can be equipped with interfaces to connect external equipment. When using the interface, the weighing instrument shall keep working normally and without error. And it can be ensured that the metering performance is not affected. External equipment generally includes: ground-sensing coil vehicle detector, infrared light curtain (grating), road gate, red-green indicator light, vehicle separator, camera, voice control equipment, computer, etc.

6.8 Anti-interference performance

It shall comply with the provisions of A.1.2 and A.4.2 in Appendix A of GB/T 21296.1-2020.

7.1 Overview

The realization of the accuracy class of quartz dynamic vehicle weighing instruments is not only related to the design, production and installation of the weighing instrument itself; but also related to the levelness, slope, curvature, road strength and other conditions of the weigh zone; and is related to the daily maintenance of the weighing instrument. Users shall have a correct understanding of this.

Quartz dynamic vehicle weighing instruments shall meet the requirements of 7.2~7.8 and the requirements of Clauses 7 and 8 in GB/T 21296.1-2020.

7.2 Road survey, site selection and layout

7.2.1 Road survey and site selection

The quartz dynamic vehicle weighing instrument shall be installed on the road section where the vehicle travels in a straight line. If there is a curve, the length of the straight section shall not be less than 64 m. The installation position of crystal quartz load receptor/sensor is selected near the length of 3/4 of the weigh zone of the straight section. It shall meet the requirements of Table 10, Table 11, Table 12, and Table 13 in GB/T 21296.1-2020.

7.2.2 Layout

The accuracy of quartz dynamic vehicle weighing instruments is related to the crystal quartz sensor's performance, number of rows, layout method, road conditions (such as road surface smoothness), and quality of buried installation. According to the application requirements, the manufacturer shall select and decide the combination method and installation quality requirements.

The layout of some typical applications is shown in Figure 1. […]

7.6 Grinding

After the potting compound particles are completely cured, the overflowed and cured compound is removed by grinding, to ensure that the top of the sensor bearing surface is flush with the road surface.

Flatness requirements: After the crystal quartz sensor is installed, the sensor and the road surface form an organic whole; that is, the crystal quartz sensor has become an integral part of the road. The flatness of the road including the sensor shall meet the requirements of Table 10, Table 11, Table 12, and Table 13 in GB/T 21296.1-2020.

7.7 Control cabinet waterproofing and grounding

The control cabinet is equipped with power supply and electronic weighing meter. The grounding resistance shall be less than 4 ohm. There shall be measures to prevent rain. It shall meet the requirements of GB/T 15395. When the basic steel bar is used as the grounding electrode of the weighing system, the grounding resistance should be less than 4 ohm.

7.8 Maintenance

During the operation and use of the equipment, the user shall conduct regular and irregular inspections and necessary maintenance, including:

a) Check and clean, to ensure that there are no falling objects such as stones, bolts and nuts in the controlled weighing area - hard objects with a size (height) exceeding 10 mm. It can cause the height difference between the sensor and the road surface, thereby affecting the weighing accuracy;

b) Check whether there are cracks on the road surface of the controlled weighing area and the bearing surface of the sensor. It shall repair the cracks with a length >0.5 m and a depth >5 mm;

c) Check whether there are pits caused by missing materials on the road surface of the controlled weighing area and the bearing surface of the sensor. It shall repair the pits on the road surface with a depth >5 mm and a size (diameter) >25 mm;

d) Check whether the pavement slabs in the controlled weighing area have phenomena such as settlements, displacements, or frost boiling. If so, it shall redo the hardened pavement in time;

e) Within 25 m before and after the controlled weighing area, no deceleration belts shall be set up which will cause the vehicle to bump and vibrate up and down;

f) The rest shall meet the requirements of Clause 8 in GB/T 21296.1-2020.

9.1 General

The test shall be carried out at the site where the quartz dynamic vehicle weighing instrument is used.

9.2 Preparation before testing

9.2.1 Requirements for test environment

The test shall be carried out under stable ambient temperature conditions. The temperature change during the test is not more than 5 °C. The temperature change rate is not more than 5 °C/h.

9.2.2 Check of installation condition

Check the installation site conditions of the quartz dynamic vehicle weighing instrument; the setting of lane separation device; the combination of the crystal quartz sensor and the road surface; and the flatness and slope of the apron at both ends of quartz dynamic vehicle weighing instrument. It shall meet the requirements of 7.1.

9.3 Weighing-in-motion tests

9.3.1 Reference vehicle

The reference vehicle used for the dynamic test shall be permitted by the relevant national technical specifications; and shall be the vehicle expected to be used by the tested quartz dynamic vehicle weighing instrument. It shall use the quartz dynamic vehicle weighing instrument system to judge the number of vehicle axles and the distance between the axles, to classify the vehicles. In addition to two-axle rigid vehicles, there shall be at least two different types of reference vehicles, to accommodate different axle structures, tractor/trailer structures, tractor/trailer connection systems and suspension systems.

At least two models shall be selected from the following three models: […]

9.3.3.4 Consider changes in reference conditions and in reference vehicles

If the vehicle shall travel a considerable distance from the control weighing instrument to the quartz dynamic vehicle weighing instrument under test, the environmental conditions shall be paid close attention. It is advisable to avoid the situation where the error that may be caused by the difference in weather cannot be determined. At the same time, it shall also consider the possible influence of fuel consumption and other factors on the weight reference value.

9.3.3.5 Determination of the conventional true value of the whole reference vehicle

Place the whole reference vehicle on the control weighing instrument for weighing, to obtain the conventional true value of the whole load of the reference vehicle.

9.3.3.6 Determination of the conventional true value of single-axle load for two-axle rigid reference vehicle

For weighing instruments that provide a single-axle load, the following method shall be used to determine the conventional true value of the single-axle load of two-axle rigid reference vehicle:

a) According to the regulations, on the control weighing instrument, perform static weighing on each single axle of the two-axle rigid reference vehicle in turn; record each single-axle load. After both single-axles are weighed, calculate the sum of the two single-axle loads - that is, the whole load (VM); record the VM value. Each single axle shall be weighed 10 times. It shall be weighed 5 times in the vehicle forward and reverse directions, respectively. Each of the above weighing shall ensure that the vehicle is stationary and stable. The axle of the vehicle shall be level. All wheels are fully supported on the load receptor. Turn off the engine. Release the brakes. The transmission is set to neutral. If necessary, wooden wedges may be used to prevent the vehicle from slipping.

b) According to formula (1), calculate the average single-axle load of each single-axle of two-axle rigid vehicle: […]

9.3.4.7 Test of abnormal speeds of passing through weighing instrument

Use a two-axle reference vehicle to carry out performance tests at the following three different speeds:

a) Greater than 10% of the maximum operating speed (vmax);

b) Less than 10% of the minimum operating speed (vmin);

c) Variable speed running test (When exceeding the maximum speed variation range, it shall be as specified by the manufacturer).

Quartz dynamic vehicle weighing instrument shall be able to detect the above abnormal operation states. Unless it can indicate or print alarm information at the same time, it shall not indicate or print weighing data.

10.1 Type inspection

10.1.1 Type inspection conditions

Quartz dynamic vehicle weighing instruments shall be subject to type inspection under the following conditions:

a) Before the first batch of new products are put into production;

b) The first batch of products after major changes in design, process, key components (crystal quartz sensor, charge amplifier, or digital data processing device);

c) When required by the national technical agency.

10.1.2 Type inspection items

During the type inspection, all the metrological requirements and technical requirements specified in Table 8 shall be inspected and tested. When the inspection conditions are limited, in accordance with the requirements of Appendix E in GB/T 21296.1-2020, the module test shall be performed using the simulation test method.

10.2.3 Test of crystal quartz sensor

Whether the crystal quartz sensor meets the requirements of Clause 6; see Appendix B for the test method.

10.2.4 On-site inspection

10.2.4.1 Preparation before on-site installation

Before the product arrives at the installation site, an on-site installation condition investigation shall be carried out. If the requirements are not met, it shall fully communicate with the user; make rectification or change the location first. After the equipment is delivered to the site and ready to be installed, check whether the installation tools are available and whether the installation materials are sufficient. Equipment installation shall be carried out when weather conditions permit.

10.2.4.2 Inspection after on-site installation

After the product is installed for the first time, on-site inspection shall be carried out.

Only after passing the inspection, can the product be delivered and attached with the corresponding product conformity certificate. The on-site inspection shall be carried out according to the items except the crystal quartz sensor test in the exit-factory inspection in Table 8. In the case of multi-lane layout, the dynamic test is carried out respectively according to the expected lanes.

A.1 General

A.1.1 Additional accuracy class of whole loads

The additional accuracy class of whole loads of quartz dynamic vehicle weighing instrument is divided into 2 classes, which are represented by symbols: 7, 15.

A.1.2 Additional accuracy class of vehicle axle loads (including single-axle load)

The additional accuracy class of vehicle axle loads of quartz dynamic vehicle weighing instrument is divided into 2 classes, which are represented by symbols: G, H.

The axle load of the same quartz dynamic vehicle weighing instrument can have different accuracy classes.

A.2 Maximum permissible errors of dynamic tests

A.2.1 Maximum permissible error (MPE) for additional accuracy class of whole loads

The maximum permissible error of the additional accuracy class of whole loads in weighing-in-motion shall take the larger value of the following a) or b):

a) Use the scale interval as the smallest unit to round the calculation results in Table A.1 to the nearest values;

b) For the first verification and subsequent verifications, 1 scale interval (1d) is multiplied by the number of times of axle weighing in whole loads of vehicle. For in-service inspection, 2 scale intervals (2d) are multiplied by the number of times of axle weighing in whole loads of vehicle.

The maximum permissible error of the additional accuracy class of whole loads shall comply with the provisions of Table A.1.

B.1 General

Before leaving the factory, it shall test the crystal quartz load receptor-signal assemble module.

The crystal quartz load receptor-signal assemble module is composed of a crystal quartz sensor and a charge amplifier; bears the load; and outputs a voltage signal.

The crystal quartz load receptor-signal assemble module shall be connected to a meter that conforms to the manufacturer's design and intended use conditions for testing.

B.2 Test devices

The test devices of crystal quartz load receptor-signal assemble module consist of a loading device, a crystal quartz sensor support platform, and a high-precision digital voltmeter (or data collector). The combined system expansion uncertainty shall not exceed one third of the maximum permissible error of the tested sensor.

The test loading device is a force standard machine or a force testing machine. It shall be equipped with a support platform with sufficient length; to ensure that the bottom of crystal quartz sensor is completely supported by the platform, and the sensor is not suspended. The maximum load value that the loading device can apply shall not be less than the max rated load on single position.

The schematic diagram of the principle and structure of the loading test is shown in Figure B.1. […]