Application of load cell and speed measurement

From the weighing principle, the instantaneous flow rate of the material measured by the load cell depends on two parameters, that is, the instantaneous flow rate is equal to the material load value q (kg/m) on the carrier measured by the load cell and the belt measured by the speed sensor The speed value v (m/s) is obtained by multiplying the two parameters. It can be seen that the measurement and stability of the speed sensor are as important as the measurement and stability of the load cell. At present, the accuracy of the load cell is generally increased to a few ten thousandths, and the speed of the speed sensor is mostly a few thousandths, so improving the speed of the speed sensor is one of the effective ways to improve the efficiency of the electronic belt scale system.

After the pulse signal of the speed sensor enters the display instrument, it usually completes the multiplication operation with the load cell signal in three ways. The first method is to transform the speed measurement pulse signal into a 0～10VDC analog signal after being reshaped and amplified, which is used as the bridge voltage of the load cell to realize the multiplication operation in the load cell; the second method is to shape the speed measurement pulse signal , After amplification, it is converted into an analog (or digital) signal, and the analog (or digital) signal amplified by the load cell is multiplied in a dedicated multiplier; the third method is to directly use the speed measurement pulse signal as a display instrument after shaping The trigger signal of the accumulator, every time it receives a speed measuring pulse signal, the accumulator will sample the input signal of the load cell. The faster the belt speed, the more times the accumulator will sample, and the sampling value will accumulate continuously, so it is implemented digitally. Multiplication operation.

In the process of using the load cell, there are many problems related to the speed sensor, but due to the very little information on this aspect, the user is often at a loss when encountering these problems. The author enumerates some solutions to problems based on his own experience and experience, hoping to learn from readers in solving such problems. The speed sensors used on electronic belt scales currently mainly include magnetoresistive pulse type and photoelectric pulse type. The analog tachometer generator-type tachometer sensor is no longer in use, and replaced by the above two digital tachometer sensors that output pulse signals.