​Uncommon failure analysis and treatment of floor scale (2)

Uncommon failure analysis and treatment of floor scale (2)
Case 2, fault manifestation: a scale instrument number irregular jump reason is difficult to find, check every sensor, meter, check the connection line method exhausted. It turned out that the junction box housing had a voltage of more than 30 volts, as did the metal parts of the case. Investigate its reason is caused by the electronic scale load power supply socket without grounding line, although is just a case, but for the balance the user has a certain influence, so in the future when installing electronic scale load power supply socket must require a ground wire, if there is no ground may cause unstable instrument display, chassis metal belt junction box electric phenomenon, and is directly affect the normal use of electronic floor scale. Although there is no ground line for the power supply used by some electronic floor scale, the above phenomenon does not appear, the reason is related to the internal structure of the meter, we will not explore, but in the new installation of electronic floor scale, there are strict requirements on the power socket.

Inspection method: if the meter number appearing in the electronic floor scale maintenance irregular jump reason hard to find charged when consider instrument shell metal parts, its method is to use digital multimeter play in voltage profile (dc, ac check respectively) instrument metal parts and one end grounded at one end, and if there is electricity, according to the communication as instrument have leakage phenomenon, if the dc transmission shows that electricity is induction. In the same way the junction box housing can be measured to see if it is live.

Solution: if the power socket can be equipped with ground wire, it is better. If it cannot be equipped with ground wire, a ground wire can be temporarily connected to the shell metal of the weighing instrument, one end is connected to the shell metal of the weighing instrument, and the other end is directly grounded.

Case 3: fault manifestation: the display number is unstable due to instrument factors, and it is difficult for people with less experience to judge the cause of this fault. It is mainly caused by incorrect calibration parameters: parameters related to the stability of the instrument include the selection of indexing value, filtering intensity and zero point incorrectness.

Instability caused by incorrect grading value selection: according to article 4.8.6 of general non-automatic weighing verification regulation JJG 555-1996; 'for scales installed outdoors without proper atmospheric maintenance measures, the calibration scale n shall not be too large (n shall not be greater than 3000; In order to improve the accuracy of the electronic weighing scale, some users choose a very small dividing value, which has little influence when there is no wind. Once there is a wind blowing, the weighing instrument will be very unstable, and even unable to be used. In addition, when the electronic floor scale used on the road is unstable, the problem of dividing value setting should be considered, the best dividing degree n is less than 3000.The improper setting of the filter intensity results in poor stability, and the filter intensity of the selected instrument should be determined according to the field situation. If the number of filter intensity selected in the instrument is small, and the operating environment condition of the scale is poor, the  instability of the instrument will be generated. Select a more appropriate filter intensity, electronic weighing indicator filter intensity selection is not strict requirements, general instruments have (0~5) levels, can meet the field use requirements. According to the field experience, small value is selected when the stability condition is good, and large value is selected when the stability condition is poor.