Shanghai Qin Chou Industrial Company specializes in selling electronic scales, digital floor scales, electronic balances, desktop electronic scales, stainless steel electronic scales, hydraulic pallet truck scales, commercial goods parts cabinets, etc. The environmental impacts on sensors are mainly as follows: 1. Extremely low-temperature environments can cause issues such as coating material melting, weld point cracking, and structural changes in internal stress of the elastic body for sensors. For sensors operating in ultra-low temperature environments, ultra-low temperature resistant sensors are commonly used; additionally, insulation, water cooling, or air cooling devices must be added. 2. Dust and humidity can cause short-circuit effects on sensors. In such environmental conditions, sensors with high sealing should be selected. Different sensors have different sealing methods, and there are significant differences in their sealing performance. Common sealing methods include filling or covering with sealant; mechanical tightening seals with rubber gaskets; welding using argon arc welding, plasma beam welding, and vacuum nitrogen filling seals. From the perspective of sealing results, welded seals are the best, while filled or covered seals with sealant are the worst. For sensors working in clean and dry indoor environments, adhesive-sealed sensors can be chosen, whereas for sensors working in humid and dusty environments, membrane heat shrinkage sealed or membrane welded sealed, vacuum nitrogen-filled sensors should be selected. 3. In highly corrosive environments, such as humidity and acidity that can damage the elastic body of the sensor or cause short circuits, sensors with good corrosion resistance and sealing, such as those with sprayed plastic or stainless steel covers, should be selected. 4. Electromagnetic fields can cause chaotic signal output from sensors. In such cases, the shielding performance of the sensor must be strictly checked to see if it has good electromagnetic resistance. 5. Flammable and explosive environments not only damage the integrity of the sensor but also pose a great threat to other equipment and personal safety. Therefore, sensors operating in flammable and explosive environments require higher explosion-proof performance: explosion-proof sensors must be selected for such environments. The sealed cover of this type of sensor must not only consider its sealing but also take into account explosion-proof strength, as well as waterproofing, moisture-proofing, and explosion-proofing of the cable lead-out heads.
Selection of Sensor Quantity and Range:
The selection of the number of sensors is based on the purpose of the electronic scale and the number of support points required by the scale body. The number of support points should follow the principle of aligning the geometric center of gravity with the actual center of gravity of the scale body. Generally speaking, if the scale body has several support points, then the same number of sensors should be selected. However, for some special scale bodies, such as electronic hook scales, only one sensor can be used, and for some electromechanical combined scales, the number of sensors should be determined according to the actual situation. The determination of the sensor range can be based on various factors such as the maximum weighing value of the scale, the number of selected sensors, the self-weight of the scale body, the maximum possible eccentric load and dynamic load, etc., to determine the appropriate range. Generally speaking, the closer the sensor's range is to the load allocated to each sensor, the higher the accuracy of its measurement will be. However, in actual operation, since the load applied to the sensor includes not only the object being weighed but also the self-weight of the scale body, tare weight, eccentric load, and vibration impact, many factors need to be considered when selecting the sensor's range to ensure the safety and service life of the sensor. The calculation formula for the sensor's range is determined after extensive practice, fully considering all factors affecting the scale body.
Formula as follows:
C = K-0K-1K-2K-3Wmax + W/N
Where C is the calculated range of a single sensor,
W is the self-weight of the scale body,
Wmax is the maximum net weight of the object being weighed,
N is the number of support points used by the scale body,
K-0 is the safety factor, usually taken between 1.2 and 1.3,
K-1 is the impact factor,
K-2 is the center of gravity offset coefficient,
K-3 is the wind pressure coefficient.
For example: A 30t electronic vehicle scale, with a maximum weighing capacity of 30t, a self-weight of 1.9t, and four sensors are used. According to the actual situation at the time, the safety factor K-0 = 1.25, impact factor K-1 = 1.18, center of gravity offset coefficient K-2 = 1.03, and wind pressure coefficient K-3 = 1.02. Try to determine the tonnage of the sensor.
Solution: According to the sensor range calculation formula: C = K-0K-1K-2K-3Wmax + W/N, we get:
C = 1.25 × 1.18 × 1.03 × 1.02 × (30 + 1.9) / 4 = 12.36t.
Therefore, a sensor with a range of 15t can be selected.
Sensor tonnages generally include 10T, 15T, 20t, 25t, 30t, 40t, 50t, etc., unless specially customized. According to experience, sensors should generally operate within 30% to 70% of their range. However, for some scales that experience significant impact forces during operation, such as railway scales, vehicle scales, and steel scales, the sensor range should be expanded so that the sensor operates within 20% to 30% of its range to increase the weighing reserve and ensure the safe operation and service life of the sensor.
Consider the applicable scope of various types of sensors: The accuracy class of the sensor includes technical indicators such as non-linearity, creep, creep recovery, hysteresis, repeatability, and sensitivity of the sensor. When selecting a sensor, do not solely pursue high-grade sensors but consider both meeting the accuracy requirements of the electronic scale and cost. The selection of the sensor grade must meet the following two conditions: 1. Meet the output requirements of the instrument. The weighing display instrument processes the output signal of the sensor through amplification, A/D conversion, etc., to display the weighing result. Therefore, the output signal of the sensor must be greater than or equal to the input signal size required by the instrument. By substituting the output sensitivity of the sensor into the matching formula between the sensor and the instrument, the calculated result must be greater than or equal to the input sensitivity required by the instrument.
Matching formula between sensor and instrument: Sensor output sensitivity * excitation power supply voltage * maximum weighing capacity of the scale / number of divisions of the scale * number of sensors * sensor range.
For example: A 25kg quantitative packaging scale, with a maximum number of divisions of 1000; the scale body uses three LBE25 type sensors, with a range of 25kg and a sensitivity of 2.0 ± 0.008mV/V, bridge power supply voltage of 12V, and an A D4325 instrument is used. Is the selected sensor compatible with the instrument?
Solution: After checking, the input sensitivity of the A D4325 instrument is 0.6Vd. Therefore, according to the matching formula between the sensor and the instrument, the actual input signal of the instrument can be obtained as follows:
(2 * 12 * 25) / (1000 * 3 * 25) = 8Vd > 0.6Vd.
Therefore, the selected sensor meets the input sensitivity requirement of the instrument and can be matched with the selected instrument.
2. Meet the accuracy requirements of the entire electronic scale, with electronic counting scale precision of 0.2g. An electronic scale mainly consists of three parts: the scale body, sensors, and instruments. When selecting the accuracy of the sensor, it should be slightly higher than the actual calculated value because practical considerations often constrain the accuracy of the scale, such as weaker scale body strength, less-than-ideal instrument performance, and harsher scale operating environments. All these factors directly affect the accuracy requirements of the scale. Therefore, requirements must be raised in various aspects, while also considering economic benefits, to ensure the goal is achieved.
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Shanghai Qin Chou Industrial Company specializes in selling electronic scales, digital floor scales, electronic platform scales, electronic vehicle scales, electronic floor scales, electronic hook scales, electronic balances, electronic bench scales, electronic desk scales, explosion-proof electronic scales, stainless steel electronic scales, hydraulic pallet truck scales, electronic drum tipping scales, industry-specific scales, commercial goods parts cabinets, etc. "Persist in enriching the people and guiding them to reduce differences together."