Large electronic scales and troubleshooting
First, the working principle Electronic scales are composed of weighing indicator, weighing sensor, junction box, weighing platform and other components, is the weight of the weighing platform under the influence of gravity generated by the sensor bridge into output and weighing value The proportional analog signal is then amplified by the meter filter and the conversion becomes a reading to the meter window.
Second, the electronic scale failure analysis and processing Electronic truck scale failure, we must first identify the fault site. Fault location is generally two major parts: First, the display instrument, and second, the scale body. The simplest method is to use the simulator to distinguish whether the fault is coming from the instrument or the scale body. Use the following method: Unplug the signal cable plug behind the weighing indicator, insert the simulator plug, turn on the instrument power supply, and observe whether the instrument is powered normal work. If it works normally, it means that there is no problem with the weighing indicator and the fault is in the scale body or junction box; if it is not working properly, it indicates that the fault is in the weighing indicator or power supply part; if the weighing platform is faulty, the limit device can be checked first. There are two kinds of horizontal and vertical limit devices, check whether the limiting device limit spacing is reasonable, the general distance is adjusted to 2mm ~ 3mm. Subsequent step-by-step inspection: (1) Junction box, now check the junction box with water vapor intrusion, if there is water vapor scrubbing with alcohol, and then blow dry with a hair dryer; find the wiring for short circuit, at the same time check each wire and ground or signal cable The outer stainless steel shield wire has no leakage and short circuit. (2) sensor, find the sensor fault is as follows: in the junction box with a multimeter to check the positive and negative excitation resistance between the resistance, the resistance is approximately 400Ω / number of sensors, with a multimeter to measure the total output of the positive output and negative output between Resistance, its resistance is approximately 250Ω/number of planes. If you find that the resistance is incorrect, press Next to continue to search and disconnect the sensor one by one. Use the method described above to measure the impedance between the positive and negative output terminals of the positive and negative excitation terminals and investigate the damaged sensor. If there is no problem in this step, press step to continue searching, place the weights on the sensor corners of each section of the weighing platform one by one, and find the +si and -si terminals of the bad sensor or disconnection sensor. The measured resistance value should be around 350Ω.
Third, the case of a case, a 30-ton electronic scales weighing error was found when the load is large, the material on the platform is not where the weight difference shows 200kg or so, and the repeatability is poor, the same car two On the next pound, the result has an error of 60kg. Failure analysis: This phenomenon is obviously the cause of the scale body. The focus of the inspection is on the balance of the scale body, whether the limit device is against the scale body and whether the sensor is damaged. After checking the scale under the body and around without foreign matter, the limit device is normal. Further inspect the sensor to measure the resistance of the four sensors are within the normal range, the output voltage is also normal, with a 20-ton weight measured eccentric load showed an angle of 119,620 kg, the adjacent three corners were: 219940 kg 319980 kg 419980 kg This judges that the 1 angle sensor is damaged, and after replacing the angle sensor, it is said to return to normal.
Case II. A 50-ton electronic truck scale. There are often signs that the signal is sometimes interrupted and sometimes good, and the meter indicates that the car has a wrong or under-loaded sign when it is on a weighing platform.
Failure analysis: After eliminating external environmental factors, check the signal cable, because the display instrument and scale are connected by a seven-core shielded cable, which will always supply power to the load cell and transmit the output signal of the sensor junction box to Instrument, inspection found that the signal line connected to the instrument was bitten by rats, intermittently connected, when the car vibrates when the pound, the meter will be shown inaccurate. Cut the end of the cable and re-strip the welding signal cable connector. Troubleshooting, the scale returned to normal.
Electronic scale case 3, a 60-ton electronic truck scale instrument shows that the unstable display value is beating, and when the same vehicle is weighed, the same material is weighed many times and the results are inconsistent.
Failure analysis: first check the external environment, whether there is debris, limit is too small. After everything is fine, dial the plug of the signal cable behind the meter and connect it to the simulator. The meter is working properly. It shows that there is no problem with the instrument and the fault is in the scale body. Check the connector of the signal wire and the connector in the terminal box. No problem. Do not suspect the fault. The output voltage of the load cell is normal. Use the detachment method, open the terminal box, and disconnect one by one. The connecting lines of sensors No. 1 and No. 6 were found to be broken when they were separated from the No. 3 sensor angle. After replacing the sensor, the scale returns to normal.
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