Common Troubleshooting of Electronic Scale

Common troubleshooting of electronic scale
With the development of commercial trade and the progress and renewal of microcomputer technology, integrated circuit technology and sensor technology, electronic scales have been widely used in all aspects of our life. Because electronic scales have the characteristics of fast, accurate, continuous and automatic, and effectively eliminate human errors, it is not accidental that electronic scales are widely used. This or that kind of fault will also occur in the frequent use of the electronic scale, so how can we solve these faults of the electronic scale?
Basic concept: a measuring instrument that uses the gravity acting on an object to measure the mass (weight) of the object. The scale equipped with electronic device is an electronic scale.
Working principle: the weighing object converts gravity into analog signal of voltage or current through the weight sensor installed on the mechanism. After amplification and filtering, it is converted into digital signal by a / D processor. The digital signal is calculated and processed by central processing unit (CPU), and the required peripheral functions and various interface circuits are also connected and applied with CPU, Finally, it is displayed digitally by the display screen.
Workflow description: when the object is placed on the scale, the pressure is applied to the sensor, and the sensor deforms, so as to change the impedance. At the same time, the excitation voltage changes and outputs a changed analog signal. The signal is amplified by the amplification circuit and output to the analog-to-digital converter. It is converted into a digital signal convenient for processing and output to CPU operation control. The CPU outputs this result to the display according to keyboard commands and programs.
1、 Specific faults and maintenance methods of electronic scale:
1. No return to zero (no return to zero, no weighing)
a. Check whether the sensor output signal value is within the standard. (total amplification code of a / D / inner code range / bottom code range)
b. If it is not within the standard, please refer to item 10 for compensation.
c. If it cannot be compensated, check whether the sensor is poor.
d. Please correct the weight according to the instructions in the manual.
2. Unable to power on
a. Please make sure it is not caused by the problems of fuse, power switch, power line and voltage change-over switch.
b. Check whether the transformer has ac110 / 220 input and ac18v output.
c. Please remove the battery and turn it on with AC power to see if it is caused by insufficient battery voltage. (when measuring the battery voltage, it should be higher than 6V. When it is lower than 5V, please charge it. If it is lower than 5.5V, and it will run out soon after full charge, please replace the battery).
3. Inaccurate weighing
a. Observe whether the internal code value is stable, whether there is friction at all parts of the sensor, whether the regulated power supply is stable, whether the operational amplifier circuit is normal, whether there are foreign matters on the circuit board of a / D circuit, and whether the feedback resistance / capacitance / filter capacitance is poor or leakage.
b. Check whether the sensor output signal value is within the standard.
c. If it is not within the standard, please refer to item 10 for compensation.
d. Use weights to test whether the weight of the four legged scale on the scale plate is average.
e. Please correct the weight according to the instructions in the manual.
4. Bad key
a. Please update the K / B test first. If the new K / b function is normal, it can be determined that the K / B is defective.
b. Measure the circuit between K / B and CPU for open circuit and cold welding.
c. Check whether the K / b foot base has poor contact.
d. Measure whether the diodes on the K / B and CPU circuits are short circuited or open circuited.
2、 General troubleshooting methods
This process should be followed to observe the fault phenomenon: analyze the cause of the fault, determine the fault location, then apply the medicine to the case, further test, check and repair the electronic scale. The simplest and fastest way to find out where the fault occurred is to use a sensing simulator. The usage is as follows: Unplug the signal line plug behind the weighing display instrument, insert the simulator plug, turn on the instrument power supply, and observe whether the instrument works normally. If it works normally, it indicates that there is no problem with the weighing display instrument, and the fault lies in the scale body, junction box and signal line. If the operation is not normal, it indicates that the fault is in the power supply part of the weighing display instrument or the front end. This method is only qualitative judgment, not quantitative analysis. When the electronic scale fails and the instrument cannot display normally, such as the instrument does not display the weight value and the display is unstable, this method is very effective to judge the fault position. However, sometimes the instrument can display normally, and when the weighing error of the electronic scale is large or the bias error is large and the repeatability is very poor, and the weighing result has deviated greatly from the actual value, it can not be judged simply. At this time, the sensor simulator can be used for simulation verification to observe the repeatability or judge with the help of standard weight and multimeter. In this case, the possibility of failure of the weighing display instrument is very small. You can directly check all parts of the scale body, focusing on the sensor limit device and other parts.

Based on the principle of outside first and then inside, the influence of external factors should be eliminated first after the failure of electronic scale. The change of external environment will have a direct impact on the weighing of electronic scale. The change of power supply, vibration, wind force and lightning will cause the instability of the electronic scale, among which wind force and lightning are force majeure. Therefore, try to avoid starting up in windy and thunderstorm weather, and take lightning protection measures and grounding protection for the electronic scale. For vibration, damping measures such as buffer device and isolation ditch can be taken to reduce its impact. The impure power supply can be solved by wiring the electronic scale separately or installing a parameter regulator.

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