Installation and calibration method of weighing sensors for weighbridge

Installation and calibration method of weighing sensors for weighbridge

　
1、summarize
Working principle of sensors: various seriesLoad CellUsing an elastic body with a strain gauge attached as a sensitive component, after an external excitation power supply is connected, a signal proportional to the applied load (force) is output. It is matched with corresponding instruments and can be widely used in various electronic scales and automatic weighing systems such as car scales, ingredient scales, packaging scales, etc. In addition, different forms of supporting instruments can also be selected to meet other application requirements such as metrology, detection, regulation, and control.
2、Sensor rated load
Conventional 10t, 15t, 20t, 25t, 30t, 40t
3、Introduction to Sensors
The elastic body of the sensor is made of high-quality specialized metal materials, and four strain gauges R1, R2, R3, and R4 are pasted on the surface of the strain sensitive area to form a Wheatstone bridge. When subjected to external force F, the elastic body deforms, causing strain gauges R1 and R3 to be stretched and the resistance value to increase; R2 and R4 are compressed, reducing the resistance value, causing the bridge to lose balance and outputting a voltage signal proportional to the external force F. Due to its high sensitivity, wide measurement range, simple circuit structure, high accuracy, and easy implementation of temperature compensation, the measuring bridge can meet the requirements of strain measurement very well.
4、Structural characteristics:
The elastic structure of the sensor is special, with good bending and torsion resistance, thereby improving the natural frequency and anti overturning, anti deviation, anti-interference and other characteristics of the sensor. The installation and connection of the sensor can use specialized connecting components, which is convenient and reliable for installation.
5、matters needing attention
5.1 Try to stay away from higher heat sources during use.
When measuring the insulation resistance of the sensor, the voltage of the megohmmeter should not exceed 100V,
5.3 When checking the insulation resistance of the sensor. The voltage of the megohmmeter cannot exceed 100V,
5.4 It is strictly prohibited to use a tramegger for testing.
5.5 should be placed at -10 ℃~50 ℃ and relative humidity& Le; Under 85% of the environment, the air should not contain corrosive gases or other substances
5.6 The sensor housing, protective cover plate, and lead connector are all sealed. Users are not allowed to open the package or forcibly pull the lead without authorization, and should send them to the manufacturer for repair.
6、General calibration methods for sensors
6.1& Ldquo; Standard weight method; Rdquo; It is one of the earliest and longest used detection methods in the development of weighing instruments, which refers to the use of weights to test the entire metrological performance of a large weighing instrument being tested. When using the standard weight method, it is necessary to test the accuracy of its maximum weighing capacity. If the maximum weighing capacity is not tested due to various conditions, at least two-thirds of its maximum weighing capacity must be tested. In the standard weight method, the error of using weights must be strictly controlled within one-third of the maximum allowable error of the weighing value. Given this usage method, large-scale weighing equipment testing often requires dozens or even hundreds of tons of measurement standard weights. The lack of measurement infrastructure in China has led to many regions being unable to mobilize so many standard weights, so this method is not commonly used in practical measurements.
6.2& Ldquo; Standard weight substitution method; Rdquo; It is currently the most commonly used method in large-scale weighing instrument testing. In response to the situation where the standard weight in China's standard weight testing method is insufficient to support testing, when the maximum weighing capacity of the tested weighing instrument is greater than one ton, we use some tools that can replace the standard weight to continue working on the standard weight. The important process of the standard weight substitution method is to find a substitute for the standard weight. To transfer all standard weights to the carrier of the tested scale, identify the weight to be replaced, calculate the error value, record this data, and then remove the standard weight. Place other loads of the same weight within the allowable error range on the carrier, so that these loads can be used to replace the standard weight and play the role of the standard weight, It can be used in combination with standard weights to meet the detection needs of the lack of standard weights. The above method can be repeated in practical applications, but it can easily cause significant errors. Therefore, we have strict regulations for this detection method: when the number of standard weights exceeds 50% of the maximum weighing capacity of the tested scale, the problem can be solved through a single weight substitution. When the number of standard weights exceeds 35% of the tested scale, the repeatability of the tested scale shall not exceed 0.3e. You can perform two weight substitutions to obtain the test results. Similarly, when the number of weights exceeds the maximum weighing capacity of the tested weighing machine by 20%, and the repeatability of the tested weighing machine does not exceed 0.3e, then four weight substitutions are required to obtain the result.
6.3& Ldquo; Integrated detection method; Rdquo; Mainly used for the detection of automatic weighing machines, the specific detection method is to determine the agreed true value of the weighed item by using the self owned device of the tested weighing machine, and then calculate the dynamic weighing accuracy index of the tested weighing machine. However, integrated detection has certain limitations, such as the need for the static weighing accuracy of the tested weighing instrument to meet certain conditions in order to support the integrated detection method, and only automatic weighing instruments can use this method, which is not widely used.
6.4& Ldquo; Overlay detection method; Rdquo; It is currently one of the detection methods that still needs to be explored, also known as comparison method. It is often used for the detection of weighing sensors. As the detection accuracy of weighing sensors is higher than that of large scales, the superposition detection method should be a feasible detection method. When using the superposition detection method for practice, it is important to note that the superposition detection method has high requirements for the strength and stiffness of the load-bearing device. Unlike weight detection and weight replacement detection, the contact surface between it and the load-bearing device is small, and the detection method of the superposition detection method may also cause deformation of the load-bearing device under external forces, which has a certain impact on the detection data. So whether the superposition detection method can be well used for the detection of large scales is still a question that our technical personnel need to consider.
6.5& Ldquo; Calculation method; Rdquo; It is also one of the detection methods that is still being explored. It calculates based on various data provided by sensors in large scales and detects the values of large scales through comprehensive control methods. During the process, it is necessary to first record the data of the large scale weighing machine in the empty inspection state, then place weights to record the output data, repeat the above steps, compare the obtained data, and obtain the required testing data of the large scale weighing machine.