The electronic truck scale mainly realizes the transformation of force and electricity
A weighing device that converts non-electric gravity into electric power, in order to be sure
To ensure the smooth realization of this function, it is inseparable from the important installation of the load cell
It is located on the fulcrum of the weighing table and needs to have a variety of good
The mechanical properties, such as stiffness, strength and fatigue resistance, are also
The resultant force required to carry the load on the table surface. Because usually at the bottom of the scale table
Setting a load cell is difficult to attract people's attention, so many times
Can not effectively play its role, and maintenance is not in place,
Shorten its service life. We should attach great importance to this.
It is necessary to play the role of load cell through reasonable application, but also to do
Good troubleshooting to reduce losses.
1 Overview of electronic truck scale weighing sensors
Electronic truck scales are usually composed of multiple parts, such as a load carrier
Device, weighing display instrument, weighing sensor, connecting piece, limiting device
And junction boxes, etc., but also often configured with other external devices, such as large screens
Screen display, computer level stabilized power supply, etc. From the electronic car to work
From the principle point of view, it is mainly to place the weighed object and load on the carrier table
Heavy cars, etc., are affected by gravity, and gravity is under the action of the carrier
Transfer to the load cell so that the load cell elastomer will appear
Deformation, and the strain gauge bridge is difficult because it is attached to the elastomer
To maintain balance. The output is then directly proportional to the weight value of the telecommunications
The signal is amplified after passing through A linear amplifier and converted by A/I
Into a digital signal, the instrument microprocessor processes the weight signal, can be
The weight data is displayed. After the printer is installed, the data can be weighed
Print and record, but this requires configuring the computer to put the metering data
Enter the computer management system, and then make comprehensive management. FIG. 1 is
Working condition of electronic truck scale weighing sensor.
Figure 1. Working diagram of electronic truck scale weighing sensor
Weighing sensor is an important conversion element in electronic truck scale.
The mechanical value can be converted into an electrical value, which can be applied to the measured object
The gravity is converted into voltage and current signals in electrons according to a certain proportion
The weighing instrument belongs to the heart part. With the rapid development of science and technology, base
The electronic weighing device of the weighing sensor is also used in various industries and fields, which can ensure the accuracy of the material weighing and the speed is very fast, especially
It is the application of microprocessors that also facilitates the automation of water in industrial production
The level is increasing, which makes load sensors unavailable in process control
Take the device [1]. From large tanks, hoppers and other weights that could not be weighed in the past
Measurement and crane scale, automobile scale and other measurement control, to the present mixed points
With a variety of raw material dosing system, automatic detection in the production process and powder particles
Feed control, weighing sensors also play an important role, on
The same is true of electronic truck scales. Load cell according to the conversion mode
See, mainly includes photoelectric type, hydraulic type, electromagnetic force type, capacitive type and
Resistance strain gauge and other types, where resistance strain gauge weighing sensors are applied
At most, it is used more in electronic truck scales. Load cell is electronic
One of the important parts of the truck scale, mainly to the original weighing information
At present, most electronic truck scales are transmitted by resistance strain form
The sensor is mainly, and only by constantly improving its quality can we ensure the normal weighing instrument
In operation, the accuracy can also be improved.
2 The specific application of load cell in electronic truck scale
2.1 Determination of working environment
In the process of selecting sensors, practical considerations need to be fully taken into account
Working conditions, ensure that the load cell used is in accordance with the actual load requirements
Sign. To carefully and carefully check the surrounding electromagnetic field environment, so that
The sensor used should not only have strong electromagnetic resistance, but also have good electromagnetic resistance
Shielding, especially in places where the working environment is harsh, sensing
The device should also have good tightness, and the type of sensor is not the same as its density
The sealing effect also varies greatly [2]. If there is a lot of dust in the environment, it is very easy
The short-circuit phenomenon of the sensor should be caused from the installation and use environment
Choose a sensor with good sealing. If there are salts and alkalis
The problem will easily bring corrosion to the sensor, and the selection of the sensor at this time
It should not only have good airtight outside, but also strong corrosion resistance.
2.2 Number and range of sensors
When determining the number of sensors, electricity should be fully considered
Sub-truck scale use, scale body and other required support points, reasonable selection
For the determination of the sensor range, it is mainly based on the maximum of the scale
Large scale value, the number of sensors, the weight of the scale body and the maximum partial load and dynamic load
Factors, etc. The sensor can only be secured if all factors are taken into account
The use of safe, prolong its life. Weighing is determined according to the sensor parameters
The number of sensors should ensure the accuracy of the sensor and the input signal of the instrument,
The conversion circuit is matched and takes into account the sensor input sensitivity, not
Can be lower than the input sensitivity on the electronic scale instrument, i.e. using load sensing
The weighing range with the best linearity is usually the full degree range
Two-thirds of it. Load cell preferably 30%-70% range, sensitivity S
Is 2MV/V, for S is 1MV/V, with a single load sensing
For example, as long as the weighing sensor responds to (output) changes and excites accordingly
The ratio of excitation (applied load) change does not exceed S=1MV/V, then
To meet the relevant regulations.
2.3 Determination of sensor accuracy level
The accuracy level of weighing sensor is mainly determined by the nonlinear,
Technical indicators such as creep, repeatability, hysteresis and sensitivity are used in the selection and
In the process of application, the accuracy level of the electronic truck scale needs to be considered in
Inside. In general, the total accuracy of the sensor used is non-linear and non-repetitive
The value of the root mean square of the three indicators and the lag is higher than the precision of the scale
The accuracy of the load cell is graded by a single sensor and a single sensor
A transmitter constitutes a sensor, and has characteristics in terms of output and input
Not good, if you choose a combination of differential, symmetrical structure and differential circuit
Differential technology can effectively eliminate zero values and reduce nonlinearity.
It not only improves the sensitivity, but also completes the temperature compensation to avoid the common
Interference caused by mode error [3]. In this way the sensor technology can be made
The technical performance is improved, and the accuracy of the weighing sensor is improved
The precision class of the weight sensor is the maximum basic error and the full amount within the range
A percentage representation of the process ratio.
In order to conform to the instrument input requirements, the sensor output message
After the number is enlarged, A/D conversion and other processing, it can be displayed in the weighing
The weighing results are shown on the table. Sensor output signal cannot be lower than
The input signal size required by the instrument is sensitive to the sensor output
Degree into the sensor and instrument matching formula, the calculation result can not be lower
Input sensitivity required by the instrument. If the rated force of the sensor is
100kg, excitation voltage is 12V, sensitivity is 2±0.0002MV/V,
Then the force is 100kg, when the excitation voltage is 12V, the output is
24±0.0024MV.
To be consistent with the accuracy requirements of the entire electronic truck scale, for transmission
The selection of sensor accuracy, the accuracy of which usually needs to be more than the theoretical calculation value
Be high. Because the theory is usually limited by objective conditions, if the scale body
Insufficient strength, lack of good performance of the instrument, poor working conditions of the scale,
Then the accuracy of the scale is difficult to meet the requirements. For each weighing sensor
For an instrument, the maximum number of degrees nLC must exceed the number of degrees certified by the instrument
n: nLC≥n, according to this provision, by weighing the number of degrees made
Restriction, that is, if the electronic vehicle scale is applied to the C3 level (3000v)
Heavy sensor, then the maximum rating is 3000e. Need for this
Enhance all aspects of the requirements, not only to have good economic benefits, but also
Make sure expectations are met.