Basic principles and common problems of multihead weigher

Author: Smartweigh–Multihead Weighter

When it comes to multihead weigher, many people think that this is just a sensor that accurately measures the net weight of an object. In fact, this is not entirely true, and it is still used in many industries. The multihead weigher shares basic principles with the previously detailed level sensors, but they don't look the same. The multihead weigher used in the industrial production and application of contemporary technological progress is ubiquitous. I will introduce the principle and application of the multihead weigher in detail in the following pickup trucks in my country.

Definition of multihead weigher A multihead weigher is a device that transforms a quality data signal into an electronic signal output that can be accurately measured. In the basic elements and evaluation methods of the key performance indicators of multihead weigher, there are qualitative differences between the old and new national standards. The key types are S type, cantilever type, spoke type, plate ring type, bellows type, bridge type, cylindrical disc type and so on.

The principle of multihead weigher has two basic structures: linear type and turntable type (disc type). Multihead weigher is composed of sliding ruler and fixed ruler (linear type) that can move relatively, or motor rotor and motor stator (turntable type). of. These two types of weighing sensor synchronizers are manufactured using the same processing technology. The multihead weigher firstly uses an insulating layer caulking agent to glue the conductive copper (0.04~0.05mm thick) on the base steel plate of non-magnetic conductive materials such as high carbon steel or laminated glass, and then uses photolithography according to the design plan. The technical or chemical etching process etches the copper into different rough-looking plan windings, which are generally referred to as printed circuit board windings.

The fixed-length and sliding scale, the windings on the motor rotor and the motor stator are not the same. The windings on the fixed-length and rotor are continuous windings, while the windings on the sliding scale and the motor stator are segmented windings. The windings are divided into 2 groups according to the segment, and they are arranged to be separated by a left phase angle of 7r in the indoor space. The principle of multihead weigher is also called sine and cosine windings.

The continuous and segmented windings of the inductive synchronizer are equivalent to the primary and secondary windings of the transformer, and work using the basic principles of alternating magnetic fields and mutual inductance. Multihead weighers can be divided into eight categories according to the conversion rules: 1. Resistor strain force type Resistor strain force type is a widely used multihead weigher, which uses the basic principle that the resistance of the resistance strain gauge changes with the change of the basic principle. The key is composed of elastic elements, resistance strain gauges, accurate measurement power supply circuits and transmission cables.

2. The oil pressure sensor has a simple and sturdy structure, and has a large detection range, but the accuracy is generally not more than 1/100. 3. The capacitance sensor uses the oscillation frequency f of the resonant circuit of the power capacitor and the positive ratio of the pole piece interval d relationship work. The capacitive sensor sensor consumes less electricity, has low engineering cost, and has an accuracy of 1/200 to 1/500.

4. The digital display data multihead weigher is a force-electrical conversion device that can change the applied force into electronic signals. A new sensor in one. The technical development trend of data multihead weigher and data measurement and verification instrument panel has gradually become a new favorite in the field of weighing technology. It has been outstanding in the industry for its advantages of simple adjustment, high efficiency, and strong ability to work on the spot. 5. The structure of plate ring type multihead weigher has the advantages of established ground stress streamline distribution, high output sensitivity, polyurethane elastomer as a whole, simple structure, stable bearing capacity, and easy production and processing.

At this stage, it still occupies a large proportion in the sensor production, and the calculation of the design formula for this type of structural sensor is not very sound at this stage. 6. After the vibrating elastic element bears the force, its original vibration frequency is positively correlated with the square root of the interaction force. By measuring the shift of the resonant frequency, the force of the measured object on the elastic element can be calculated, thereby calculating its quality.

There are two types of vibration sensors: vibrating wire and tuning fork. 7. Mobile phone gyro ceremony The mobile phone gyro ceremony sensor has a fast response speed (5 seconds), no backward conditions, good temperature characteristics (3ppm), small vibration hazards, accurate frequency measurement and high precision, so it can obtain high screen resolution and high measurement accuracy. 8. Optical type includes grating ruler type and code disc type.

Optical sensors have been mainly used in electromechanical engineering fusion scales. The multihead weigher isn't quite right, and it has flaws that can't be avoided. 1. Frequency characteristics Discrete system The frequency characteristics of the capacitive sensor multihead weigher are discrete systems. Although the differential signal type is used to improve, it is unlikely to be completely eliminated.

Other types of capacitive sensors only have a linear frequency characteristic when the fringing effects of the electrostatic field are ignored. Otherwise, the extra capacitance caused by the fringe effect will immediately add up to the inductor power capacitors, making the frequency characteristic of the system discrete. 2. Parasitic capacitance harms the original capacity of the multihead weigher of the large capacitance sensor, while the wire capacitor connecting the sensor and the electronic circuit, the stray capacitor of the electronic circuit and the capacitor composed of the inner plate of the sensor and the surrounding electrical conductors are parasitic. The large shortage of capacitors not only reduces the sensitivity of the inductor, but also the capacitors are often changed arbitrarily, which will make the instrument and equipment very unstable during operation and endanger the measurement accuracy.

3. The output impedance is high and the load capacity is poor. The volume of the multihead weigher of the capacitive sensor is limited by the geometrical specifications of its electric stage. It is not easy to make it very large. Law. Therefore, the output impedance of the capacitive sensor multihead weigher is high, so the load capacity is poor, and it is vulnerable to external influences to cause unstable conditions, and even cannot work in severe cases. Weighing equipment made by multihead weigher has been widely used in various fields to complete the rapid and accurate weighing of raw materials, especially with the emergence of microprocessors, the continuous improvement of the level of automation technology in the whole process of industrial production , multihead weigher has become an indispensable equipment in process management, from the weight measurement of large and medium-sized tanks and silos that could not be weighed before, as well as its crane scales, car scales and other measurement operations, to mixing and dispatching multiple The automatic batching system of various raw materials, the automatic identification in the production process and the control of the powder feed amount all use the multihead weigher. At this stage, the multihead weigher is basically applied to all weighing industries.

1. The reason for the deviation of the characteristics is caused by the machine itself, including the DC drift value, the error of the slope or the nonlinearity of the slope. In the end, there will be a difference between the idealized migration characteristics and the real characteristics of a machine. 2. The reason for the deviation of the multihead weigher is the reason for the deviation caused by the actual operation, including the incorrect placement of the probe, the wrong insulating layer between the probe and the precise measurement location, and the cleanliness of the gas or other gas. Incorrect process, incorrect placement of smart transmitters, etc. There are various reasons for deviation caused by incorrect actual operation.

3. The reason for the deviation of the dynamic performance The sensor that applies the static data standard will have strong vibration damping, so the response to the change of the key parameters is relatively slow, and it even takes a few seconds to respond to the step change of the temperature. Some weighing machines with a delay time feature are the cause of deviations in dynamics when responding to rapid changes. Response speed, amplitude dropout, and phase difference dropout are all causes of skewed dynamics.

4. The reason for the deviation of the insertion is that when a sensor is inserted into the system software, the main parameters of the accurate measurement are changed and the deviation is caused. The application of a system to an excessively large smart transmitter, the dynamic characteristics of the system software is too slow, and the self-heating in the system software loads too much energy, etc., all of which will cause the insertion deviation. 5. Reasons for deviations in the natural environment The multihead weigher application is also affected by environmental hazards such as temperature, shaking, vibration, altitude, compound evaporation, etc. These factors are very easy to cause deviations in the natural environment.

Resistor strain force multihead weigher is one of the most widely used multihead weighers. Its durability, reliability and accuracy are beyond doubt. To some inconvenience, what should be paid attention to when using multihead weigher? 1. Pay attention to the application of high temperature, smoke, humidity and cold in the natural environment, as well as the environment with high corrosion, and the natural environment of the magnetic field, which will cause serious damage to the multihead weigher. Therefore, it is necessary to pay attention to the use of the multihead weigher in the natural environment, or select the relative multihead weigher in a clear environment. 2. Avoid super important to prevent damage to the multihead weigher caused by overweight, even if the multihead weigher has a certain load capacity.

3. The power supply circuit is connected to the display information power supply circuit or the power transmission line drawn from the power supply circuit should be shielded twisted pair cables. The sensor output data signal reading power supply circuit cannot be connected with some machines that can affect high-calorie food. equipment together. 4. Avoid dirt contamination of the sensor Dirt contamination of the sensor may harm the movement and precision of the sensor. You can set some around the multihead weigher“Separator”Or cover the sensor with a thin metal sheet.

5. Application of electrical equipment bypass In order to better prevent arc welding current or damage caused by lightning strikes, the inductor should use hinged copper core wire (section about 50mm2) to generate electrical equipment bypass, and to prevent obvious heat transfer. 6. Install the level gauge In order to better ensure the precision of the weighing scale, the level is adjusted by the level gauge to solve the installation plan of the single sensor installation base. In order to better make the load borne by each sensor basically the same, the installation surfaces of the installation bases of several sensors can be adjusted to a level surface as much as possible.

7. Handle and handle the multihead weigher with care. Avoid all shocks, falls, etc., handle with care. In addition, the base on which the sensor is installed should be leveled and cleaned, with sufficient compressive strength and rigidity, without all oil slicks, adhesive tape, etc. 8. To avoid some lateral force functions, structural parts with automatic precise positioning or calibration functions such as ball rolling bearings, joint bearings, and precise positioning tighteners can be selected on the sensor.

9. The power plug and control wire should be twisted together at a level of 50 rpm/m. If the sensor power cord must be increased, a specially made sealed cable terminal should be used. If the communication cable is long, it should be considered to select the cable containing the wireless repeater amplifier to compensate the power supply circuit. 10. The communication cable of the protective grounding sensor cannot be arranged in parallel with the weak current power plug or control line.

Summary: I will introduce the multihead weigher in detail here. I firmly believe that with the development of technology, the multihead weigher may be used in a large number of industries with its characteristics and advantages, which will bring convenience to everyone's daily life.

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