Electronic weighing apparatus is a digital weight measuring instrument with electronic devices. A weighing sensor, an operational amplifier, an a/D conversion integrated circuit, an intelligent singlechip, a display drive and display circuit, a keyboard circuit, a multifunctional interface circuit and an AC/DC/charging/storage/voltage stabilizing circuit. The phenomena and root causes of all kinds of faults are strange. 1.Do not return to zero (do not return to zero, do not weigh) A. Check whether the output signal value of the sensor is within the standard. (Total amplification code of A/D/range of inner code used/range of bottom code) B. If it is not within the standard, please refer to the tenth item for compensation. C. If the compensation cannot be made, please check whether the sensor is defective. (Please test according to Item 8) D. Please correct the weight according to the instructions. 2. Inaccurate weighing A. Observe whether the internal code value is stable, whether there is friction at each part of the sensor, whether the regulated power supply is stable, whether the operational amplifier circuit is normal, whether there is foreign matter in the circuit board of the A/D circuit, and whether the feedback resistor/capacitor/filter capacitor is defective or has leakage. B. Check whether the output signal value of the sensor is within the standard. C. If it is not within the standard, please refer to the tenth item for compensation. D. Use weights to test whether the four-foot weighing of the scale is even. (If it is uneven, please refer to the ninth item for grinding and weighing) E. Please correct the weight according to the instructions. 3. Unable to power on A. Please make sure that it is not caused by the problem of fuse, power switch, power cord and voltage switch. B. Check whether the transformer has AC110/220 input and AC18V output. C. Please remove the battery and turn on the machine with AC power supply to find out whether it is caused by insufficient battery voltage. (Measure the battery voltage, which should be higher than 6 V. If it is lower than 6 V, please charge it. If it is lower than 5.5 V, please replace the battery if it is out of power soon after full charge.). 4.Poor display A. Connect the normal LCD pin to the LCD of the maintenance scale in parallel by hand, and then start the machine to observe whether the normal LCD has the same condition. If not, it can be determined that the LCD is defective. B. Check the CPU pin for oxidation, cold welding or short circuit. Whether the pins and holes of the C. LCD are oxidized, cold-welded or short-circuited. D. Check the circuit between CPU and LCD for open circuit. 5. Bad keys A. Please update the K/B test first. If the new K/B function is normal, it can be judged as a defective K/B. B. Measure the circuit between K/B and CPU for open circuit and cold welding. C. Check the K/B foot for poor contact. D. Measure whether the diode on the circuit of K/B and CPU has short circuit or open circuit. 6. Unable to weigh to full load A. Check whether the output signal value of the sensor is within the standard. B. If it is not within the standard, please refer to the tenth item for compensation. C. If the compensation cannot be made, please check whether the sensor is defective. (Please test according to Item 8) D. Replace the sensor if it is unstable or cannot be compensated after compensation. E. Check whether there is interference of internal wireless material or protective device. F. Whether the battery voltage is above 6 V. G. Replace L/C to test whether it is caused by poor sensor. 7. The battery cannot be charged A. Please make sure that it is not caused by the problem of fuse, power switch, power cord and voltage switch. B. Check whether the transformer has AC110/220 input and AC18V output. C. Connect the battery to the board and remove the PIN. Measure whether the charging voltage of the board is about 7.2 V. If not, check the relevant circuit of the power supply. D. Check whether the diode near the PIN at the input end of the transformer is normal. E. Replace the battery. 8.Sensor Defect Discrimination A. Static method: use the ohm range of the multimeter to measure whether the E + to S +, S- (or E- to S +, S-) resistance of the sensor is the same. Generally speaking, if the error is more than 0.5Ω, compensation is required. If the error is too large (more than 2Ω), it is recommended to replace the L/C. B. Dynamic method: correctly connect the sensor back to the motherboard, and use the DCV file of the digital ammeter (more than four and a half digits are preferred) to measure whether the voltage of S + to ground and S- to ground are equal (preferably 0 error). If they are not equal, the sensor compensation is required. 9.Angular differential adjustment (single sensor) A. Carry out weight correction first. B. Measure the four corners of the scale with 1/3 weight of the full load to see the displayed value. C. Use the file to grind the side with the lowest weighing value in the 1-4 angles, and then press to return to zero. (When grinding the scale for the first time, please test the force with small force to avoid damage to the sensor.) D. Repeat 2 ~ 3 actions until the error of the four corners of the scale is within ± 1 jump based on the center, and then correct the weight. E. If the error of the four corners of the scale is too large, and it is still too large after grinding the scale, it indicates that the sensor has failed, or the method of grinding the scale is wrong. F. Pay attention to the sensor specification when grinding the scale. The lighter the full load is, the lighter the grinding force is. 10.Sensor compensation A. If the output signal of the sensor is too high, please add a resistor (50K ~ 2.2MΩ depending on the situation) between the "E + S-" of the sensor to make the signal value reach the normal range (the lower the resistance value is, the lower the output signal of the sensor is). B. The output signal of the sensor is too low or -ERR. Please add a resistor (50k ~ 2.2MΩ depending on the situation) between "E + ~ S +" of the sensor to make the signal value to the normal range (the lower the resistance value is, the higher the output signal of the sensor is). Appendix: Method for Detecting Amplification Code of A/D Circuit Adjust the electronic scale to the internal setting state (make it display the current internal code state), apply the full weighing weight, record the amplification code value, and their relationship is: bottom code value + full weighing amplification code + safety area code electronic