A fault occurred in an electronic scale, which required analysis, inspection, and adjustment. This is a relatively complex and meticulous task that requires both theoretical knowledge and practical skills. During the process, I developed an effective method called the "Segmented Fault Detection Method." Its content is as follows: Based on the working principle of the electronic scale (i.e., the weight on the scale platform generates a signal proportional to its weight through the deformation of sensors under gravity, then the weighing instrument converts this signal into a digital display), faults can be detected by checking each of the five parts of the scale system one by one: the scale body, the weighing sensor, the junction box, the wiring, and the weighing instrument. Below is an overview of the Segmented Fault Detection Method.
### Segmented Parts
#### Inspection Content
**Scale Body**
- Whether the limit screws are too tight or stuck;
- Whether there are any foreign objects underneath the scale body;
- Whether there is any friction around the scale body.
**Sensor**
- Whether all sensors are fully in contact with the ground;
- Whether any sensor is damaged or has abnormal output signals;
- Whether the base of any sensor has sunk.
**Junction Box**
- Whether the junction box is damp;
- Whether there is any cold soldering or corrosion on the circuit board inside the junction box;
- Whether the terminals are loose or crossed.
**Wiring**
- Whether the wiring is damaged;
- Whether the wiring connectors have cold soldering or loose connections;
- Whether the connectors are damp.
**Instrument**
- Whether all internal components of the instrument are securely fastened; whether the voltage at various measurement points is normal;
- Whether there is any burnt, cold-soldered, smoking, or sparking phenomenon on the circuit board;
- Whether there is any abnormal noise from the current rectifier;
- Whether relevant components are overheating;
- Whether there is any burnt smell inside the instrument.
### Fault Phenomenon:
The weighing instrument does not return to zero.
### Maintenance Process:
A 100t electronic scale was functioning normally when vehicles were on the scale platform but failed to return to zero after the vehicle left. This issue occurred repeatedly during testing. According to the segmented fault detection method, we first checked the instrument using a simulator, confirming it worked normally. We then inspected the wiring, finding no damage. Using our own instruments, we tested the junction box and sensors, verifying they were also functioning properly. At this point, we preliminarily judged that the problem lay with the scale body.
According to feedback from the scale operator, the scale did not exhibit this issue during the day or night but only during midday. This strengthened the suspicion that the scale body's fault was related to temperature. Since it was midday in summer with temperatures reaching 40°C, the iron plate of the scale body reached approximately 50°C. It was possible that the limit screws had expanded due to heat and were jamming the scale body. Subsequently, upon opening the cover of the scale body, we discovered that the gap between the limit screws was too small. When the temperature rose, the limit screws expanded due to heat and jammed the scale body. After loosening the limit screws, the scale returned to normal operation.