Electronic scales are not accurately attracted by magnets. Can you calibrate it?

The mechanical scale measures the mass of the measured object by using the principle of lever displacement, which is a kind of analog measurement, so the displayed value has great error.

Based on the principle of sensor measurement, electronic weighing instrument changes the resistance of strain gauge attached to external pressure through the deformation of sensor elastic beam, and outputs an analog electrical signal proportional to the measured object to AD circuit under the action of excitation voltage. The AD circuit of the electronic weighing instrument modulates, amplifies, filters, samples and integrates the analog signals sent by the sensors, outputs stable and efficient digital signals, and sends them to the central microprocessor (CPU). The CPU controls the internal working program and displays the weight value of the measured object through the display circuit.

The calibration of weighing is based on the quality of national standard value (legal weight). When the output digital code (BCD code) is consistent with the program calibration code compiled by the internal program memory of CPU, the weighing calibration can be completed.

Analog weighing instruments are calibrated directly with standard weights, which has low technical content and is easy to be faked (depending on the quality of standard weights).

The weighing calibration of electronic scales requires standard weights, but also calibration passwords. The calibration password is held by the weighing instrument manufacturer and kept strictly confidential.

The illegal calibration of electronic scales is carried out by using the allowable range of the mass value of standard weights and the calibration code value of calibration procedures, because the calibration digital value has a certain spatial range (for example, an electronic scale with a maximum weighing of 150kg can be calibrated as a 50kg display value in the range of 12000 ~ 18000). If the actual weight of the calibrated weight is 49kg and the calibrated display value is 50kg, then the actual weight when the electronic scale shows 150kg is 147kg. It goes without saying what consequences this scale will have in market transactions. This is the importance of legal measurement in the national economy.

After installation, check whether all parts of the scale are well connected. The scale body should not contact with any part of the foundation, and the distance between the scale body and the surrounding fenders is 10 mm ~ 15 mm.

Before commissioning, turn on the power switch to warm up for 15 minutes, and try to use a vehicle close to the maximum weight to pass through and stop on the load-bearing platform for many times, and tighten the high-strength bolts of each load cell with a torque wrench.

1. Measure the output voltage of each load cell in turn with a digital voltmeter. If there is any inconsistency, adjust the corresponding two precision adjustable resistors in the junction box to reduce the difference between them. However, we must pay attention to the adjustment. The two adjustable resistors should rotate in the same direction and by the same amount. When rotating clockwise, the resistance decreases, the output voltage increases and the displayed value increases, and vice versa. Until the output of each load cell is adjusted to be consistent.

Generally, the weight method can be used for debugging, that is, the weights with the maximum weighing value of110 are placed in the center of the bearing table and above each weighing sensor in turn, and the difference of the output of each weighing sensor is accurately measured by the real difference method, and at the same time, the two precision adjustable resistors corresponding to each weighing sensor are adjusted respectively to reduce the difference, but the rotation direction and amount are the same.

2. After debugging the key points, evenly add the weights equivalent to the maximum weight to the bearing table. After the displayed values are consistent with the weight values according to the positions and methods introduced in the instructions of various weighing displays, remove the weights and confirm that the empty scales display "0". Finally, the maximum weighing is divided into several parts, which must include all weighing points with minimum weighing, maximum weighing and tolerance variation, and the weighing error of each point is required to be no greater than the maximum tolerance requirement of each measuring point.

3. Refer to the instruction manual of weighing display (professional technical manual), check the correctness of various function keys, and improve the weighing accuracy of electronic truck scale.

Common sense of using electronic scales