Shanghai Qin Chou Electronic Scale href="http://www.qinchoush.cn">Electronic Scale Electronic Platform Scale: Basic Knowledge Training for Electronic Vehicle Scales, Scale Knowledge Training Floor Scale, Electronic Floor Scale, Vehicle Scale, Electronic Scale, Electronic Pricing Scale, Electronic Crane Scale
1. What is the difference between calibration and inspection?
Calibration: A mandatory inspection of whether the scale's metrological performance meets national legal requirements, usually carried out by national metrology management departments.
Inspection: Checking if the scale in use meets the calibration regulations; whether it is in good working condition; and whether its operation is correct and reliable. This non-mandatory inspection can be conducted by both manufacturers and users.
2. Which scales need to undergo calibration?
1 Newly manufactured or newly installed scales;
2 Scales recently imported from abroad;
3 Scales that have reached the end of their calibration cycle;
4 Repaired scales;
5 Scales required by users or whose seals are invalid due to some reasons and need calibration;
3. How does the state specify the maximum allowable error for electronic vehicle scales?
Initial Calibration: For 0≤m≤500, the maximum allowable error is +0.5e; For 500＜m≤2000, the maximum allowable error is +1.0e; For 2000＜m≤10000, the maximum allowable error is +1.5e;
Subsequent Calibration: The maximum allowable error is the same as the above standards.
In-use Inspection: The maximum allowable error during in-use inspection is twice the maximum allowable error of the initial calibration.
4. What are the state requirements for errors in the weighing results of vehicle scales?
The error value of any single weighing should not exceed the maximum allowable error of the scale.
5. How to check if the weighing error of a vehicle scale is within the specified range?
1 Perform repeatability testing: The difference in results obtained from repeated weighings of the same load should not exceed the absolute value of the maximum allowable error of the scale.
2 Perform eccentricity testing: The error in readings of the same weight at different positions should not exceed the maximum allowable error for that capacity.
6. What are the state requirements for the error of standard weights used in calibration?
The error of the standard weights used in calibration should not exceed one-third of the maximum allowable error of the corresponding capacity.
7. What is the accuracy requirement for the zero-setting device of a vehicle scale to meet national calibration requirements?
After zero-setting, the influence of zero-point deviation on the weighing result should not exceed 0.25e.
8. What are the markings on a scale?
Compulsory marks: Manufacturer's name, trademark; Accuracy class; Maximum capacity, minimum capacity, division value, manufacturing license mark and number. Other marks: Serial number, etc.
9. What impact will不合格calibration of a vehicle scale have on the manufacturing enterprise?
Scales that fail the initial calibration and subsequent calibration will be issued a calibration result notice and shall not be manufactured, sold, or used. Scales found不合格during in-use inspections shall not be used.
10. Into how many categories can sensors be divided according to the signal output method? What are the characteristics of each?
They can be divided into two categories: digital sensors and analog sensors. Digital sensors output digital signals such as quantity and weight; Analog sensors input analog signals such as voltage and current to the instrument. In addition to all the advantages of analog sensors, digital sensors also have the following advantages:
1 Strong anti-interference ability: Not affected by temperature changes and electromagnetic interference;
2 Intuitive digital display, easy to detect faults: The status or slight changes of each sensor can be intuitively indicated on the instrument, making it easy to discover and find which sensor has problems; Analog sensors cannot reflect the specific situation of each sensor through the unified value input from the junction box to the instrument (the sensitivity of several sensors must be unified), and its disadvantage is that it belongs to a new type of sensor, although its excellent performance has been verified, but the repair technology is not yet mature and widespread. Once a fault occurs, it is inconvenient to repair or replace parts, easily delaying user operations.
11. Is four-wire connection or six-wire connection better between the junction box and the instrument? Why?
Six-wire connection is better. Four-wire connection can easily lead to the following issues: ① Changing the length of the signal wire will cause errors in the weighing result: When the length of the signal wire changes, the resistance of the signal wire will change accordingly, causing a change in the excitation voltage applied across the sensor terminals, thus generating an error. To reduce the error, recalibration must be performed; ② When the temperature changes, the resistance of the signal wire will definitely change, causing a change in the excitation voltage output, thereby leading to weighing errors; ③ Instability of the excitation power supply itself will also cause errors. With the six-wire system, the signal wire for the sensor is six-core. After adopting the six-wire system, the added two cable cores act as the reflection line for the bridge voltage connected to the reference voltage input terminal of the instrument. This connection format ensures that the accuracy of the scale only depends on the sensor, amplifier, and A/D converter (the latter two are internal components of the instrument), and is independent of the length of the cable, temperature, and voltage stability conditions. Therefore, the six-wire system is better than the four-wire system.
12. What are the environmental requirements for the normal operation of a vehicle scale?
① Operating environment humidity: ≤95%
② Operating power supply: 220V error range: -15%～+10%, 50HZ maximum error: ±1%
③ Operating environment temperature: Sensor -20℃～60℃; Instrument -10℃～40℃
④ Maximum safe load: 125%F.S of the maximum capacity
⑤ Temperature change: ≤5℃/h
⑥ For special environments, determine based on needs
13. How are sensors classified typically? What are the characteristics of each?
1 Sensors can be classified into column-type, bridge-type, spoke-type, cantilever beam-type, etc.
2 Characteristics of column-type sensors: Low cost, small size (easy maintenance and repair), excellent sealing performance, suitable for humid environments, strong load-bearing capacity; Their disadvantages are low sensitivity (if the weight increase or decrease is small, it is difficult to display on the instrument) and low stability (easy drift, inaccurate readings). Within a certain range, they have better anti-eccentricity and anti-lateral capabilities than bridge-type sensors, but limit devices must be assembled. Spoke-type sensors: The sensors themselves are short in height and can withstand large lateral forces; Anti-eccentricity, insensitive to force point changes; Suitable for low-height scales like axle weighers. Cantilever beam-type sensors have the following characteristics: Strong anti-eccentricity capability, high accuracy, similar sensitivity when the sensor is under tension and compression, so particularly suitable for simultaneous tension and compression measurements; Low profile, small size, light weight, easy to assemble and maintain; Disadvantage is low full-scale accuracy. Bridge-type sensors' characteristics are high sensitivity, strong stability, automatic reset (due to the steel ball in bridge-type sensors), no need to assemble limit devices; Disadvantage is that within a certain range, they are easily affected by lateral forces, with larger errors than column-type sensors.
14. What is shielding? How to prevent shielding?
In the manufacturing industry, magnetic fields, radio frequency (broadcast, television, communication, radar, etc. transmission devices) noise, vibrations, etc., all affect the transmission of voltage signals in vehicle scale signal lines. To prevent these effects or minimize them, shielding technology is produced. Shielding works from two aspects:
1 Grounding of sensors to shield the sensors;
2 Instrument shielding: One is to design the instrument housing structure for anti-interference; Two is to design the shielding between the internal circuits and components of the instrument, including the transformer shielding design, amplifier shielding design, and grounding.
15. What materials are commonly used for sensors now?
Nowadays, there are three common materials for sensors: Stainless steel sensors: Mainly used in corrosive environments such as food, chemical, and pharmaceutical industries; Alloy steel: Used in non-corrosive environments; Aluminum alloy: Generally used in low-range and low-cost applications.
16. What are the requirements for the construction of the base plate plane for each weighing point when constructing the foundation of a vehicle scale?
Each plane degree error should be within 3-5mm.
17. What are the components of a sensor? What functions do they serve?
Three parts: Elastic body, strain gauge, and detection circuit. The function of the elastic body is to transmit the gravity of the heavy object itself and apply it to the strain gauge; It causes the strain gauge to deform ideally, truly reflecting the magnitude of the force. The function of the strain gauge is to deform under force, changing its own resistance value. The function of the detection circuit (actually a Wheatstone bridge) is to convert the resistance change into an electrical signal output.
18. What are the requirements for the location selection of the vehicle scale foundation?
1 The site facilitates vehicle entry and exit and turning;
2 Try to avoid wind mouths;
3 Easy drainage, good ventilation and air circulation, convenient for lifting and placing the scale body;
4 No high-voltage lines within 50 meters around the ground part;
5 No cables, optical cables, pipelines, or pipes in the hidden part.
19. For abnormal lengths, is a three-section scale body better or a four-section scale body better?
Three sections are better. Because a three-section scale body has 8 sensors, while a four-section scale body has 10 sensors. In terms of cost: A three-section scale body saves material and sensors compared to a four-section scale body, thus saving costs; In terms of accuracy: Due to the different sensitivities of each sensor, as the number of sensors increases, the possible weight display error also increases, easily causing inaccurate weighing. However, if using the same sensors, compared to a four-section scale, a three-section scale has a smaller maximum load (including allowable overload) and less safety margin. Additionally, because each sensor bears more force, it is also easier to damage the sensors.
20. What does baud rate mean?
Data transmission speed is called baud rate.
21. What is the function of a filter?
To reduce the error caused by noise signals on the weighing result.
22. What is zero tracking?
When there is no load on the scale, the instrument should display zero. However, in reality, due to changes in external temperature, wind, radio frequency, noise, vibration, etc., the instrument reading often is not zero, but shows zero drift. Also, when a large amount of material is scattered on the scale body, the instrument reading will appear. Therefore, compensation must be made for these minor changes to keep the reading at zero. This is called zero tracking.
23. What are the main uses and characteristics of an electronic pricing scale?
The weighing range of an electronic pricing scale is small, generally between 3 kg and 15 kg. It is low-cost, small-sized, very portable and easy to move, highly accurate, stable, easy to repair, and provides intuitive displays (some can show dual-sided displays). Therefore, it is popular among stores, supermarkets, and individual vendors. It belongs to Class III scales and generally uses cantilever beam sensors. Its main function is to accurately, intuitively, and conveniently calculate the total price and display it, and it is suitable for different situations. Its functions include: zero setting, tare removal, unit price setting, weighing, and calculation and display of the total amount, as well as giving change. The displayed content includes: unit price, (weight) quantity, total price (amount). Its weighing method can be either one-time weighing or frequent cumulative weighing; it can weigh a single item or multiple items. Specific operation and operating environment requirements are detailed in its user manual.
24. What is the principle of operation of a belt scale?
Common belt scales come in two types: speed measurement and length measurement. Speed measurement is more common. Its principle is to separately measure the weight of the conveyed material and the conveying speed, and then convert them into signals via corresponding circuits, displaying the weighing result on the instrument. It can be expressed by the formula W=QVT, where: W is the material weight; Q is the material weight per unit length; V is the belt speed; T is the continuous operating time. The principle of length measurement is to divide the material on the belt into equal segments using a photoelectric distance detector, sample the weight of each segment at regular intervals, take the average value of the weight of each segment, and finally sum them up to get the total weight of the material over a certain distance.
25. How are sensors categorized?
Sensors are classified into different types according to different classification methods.
By force application method: Compression, tension, beam, and multi-functional types. By data output standard: Analog sensors (output as analog signals such as voltage, current) and digital sensors (output as direct digital signals such as kilograms, tons). By application temperature: Normal temperature sensors (general-purpose sensors suitable for ordinary operating environments); Ultra-low temperature sensors (specialized sensors suitable for ultra-low temperature environments such as metallurgy, nuclear power); Ultra-high temperature sensors (specialized sensors suitable for environments below -30℃, such as freezing experiments).
By structure: Column-type, bridge-type, cantilever beam-type, spoke-type, etc.
26. What are the main aspects of external protection for sensors?
Internal protection mainly involves ensuring that each solder joint inside is securely and solidly soldered. External protection mainly involves ensuring that the signal wires are resistant to aging and have good insulation properties, preventing squeezing, twisting, and pulling of the signal wires.
27. Why is a limit device necessary?
During actual weighing, there often exists a certain amount of horizontal force (such as the force when a car drives onto the scale or brakes after driving onto the scale). However, users require that the indication stabilize quickly and read values rapidly, meaning the scale body should remain nearly fixed even when subjected to forces. Therefore, a limit device is used to meet customer requirements. According to authoritative tests, for a 16-meter-long vehicle scale, braking can produce nearly 30 tons of horizontal force. Trains traveling on smooth tracks can also generate 4 tons of horizontal force. Generally speaking, horizontal forces easily cause tipping and rotation, so setting horizontal limits is important.
28. How to design reasonable limit devices based on user conditions?
Users' application conditions vary, so limit devices should be designed in different forms. Generally, limit columns should have sufficient strength to withstand large horizontal forces and maintain a 2-3 millimeter gap with the fixed body (otherwise, the limit device itself will be stressed, creating bypasses, affecting weighing, and causing errors). Specifically:
1 For large-platform electronic vehicle scales, track scales, etc., where the scale platform is not allowed to sway back and forth, setting the horizontal limit device at the four corners of the scale platform is very unreasonable because the thermal expansion and contraction of the scale platform can lock up small limit gaps. Therefore, limiters must be installed in the middle of the scale platform so that the entire platform can freely expand and contract while still being "fixed" (relatively fixed).
2 For hopper scales, container scales, etc., horizontal rod limits should be used to prevent horizontal displacement, horizontal changes, and complete tipping. Specifically, the connection points at both ends of the rod should be flexible or pliable to prevent the generation of side forces, causing errors (inaccurate weighing).
29. When sensor signal wires are gathered into the junction box, they are often left longer. How should this extra length be handled?
It should be retained and not cut. Cutting it can lead to data drift, jitter, and increased sensitivity (if the resistance of the signal wire is sufficiently large, cutting 10 meters will increase the full-scale output value by 20-40 kilograms, causing corner errors).