The topic we are talking about today is about the weighing problem of concrete mixing plant . The cost of the mixing plant is bound to be higher when the amount is too large, and the quality of concrete cannot be guaranteed when the amount is low. Therefore, don’t relax the inspection and maintenance of the weighing system at any time. So, in everyday situations, what should we do when we encounter the weighing problem of the mixing plant ?

Know the weighing sensor of concrete mixing plant

The weight sensor is a device which changes the object mass signal into measurable electrical signal output.

From the above definition, we can know that the weighing sensor is an electrical element, through which we can measure the weight of the raw material we need.

The most commonly used load cells in general concrete mixers are shear beam and s-shaped pull type weighing sensors, as shown in the two figures below.

In the concrete mixing plant , the measurement of aggregate, powder and water is made of shear beam type weighing sensor, while the s-shaped pull-type weighing sensor is mainly used in the measurement of admixture.

Both the working principle of about the same, sensors built into the elastic element, if there are external forces, on which the elastic element deformation will occur, and adhesion on the resistors, so will produce deformation resistance resistance will change, through the change of the resistance, the output of the sensor will change the current or voltage, this process will object is converted into electrical signals, the weight of the electrical signal through interpretation, finally through the display screen, this is what we are weighing the weight of the object value.

2. Common fault causes and treatment methods of sensors in concrete mixing plant

1. No weighing reading

This fault is generally more common, a certain weighing value is zero, regardless of whether there is anything above it, its weighing value is always zero.

The above faults are caused by the following reasons: a, damage of sensor, b, circuit break, c, fault of signal transmitter, d, poor contact of junction box

A. Sensor damage: the voltage value of the sensor output signal line when detecting the null and the raw materials above. If the values of both are the same, the sensor is damaged. The sensor output signals are detected according to the following figure. The working principle and boundary mode of different brands of sensors are basically the same. The following figure shows the connection principle of 6-wire sensor.

B. short circuit in the circuit: if the sensor is not damaged, it can be checked to see if there is any break in the circuit. The method is to follow the circuit of the sensor to see if there is any mark of skin or shear.

C. Fault of signal transmitter: after the above two reasons are eliminated, we finally check the signal transmitter. Its detection method is basically similar to that of the sensor.

D. Poor contact of the junction box: this is mainly because the connection is not made firmly.

2. The weight value fluctuates

This phenomenon is manifested in the fluctuation of a certain weight value, which is beyond the normal error range.

Main reasons: a. large mechanical vibration near the sensor; b. high frequency signal transmitter near the mixing station (including mobile signal tower, substation with ultra-high voltage)

If the hopper attached to the sensor mounting seat is purely mechanical vibration, the deformation of the sensor will be constantly changing. Therefore, the weight value of the weight will cause the fluctuation.

As for the problem of signal interference near the concrete mixing station, it should choose a reasonable site at the beginning of the construction of the station and stay away from these interference sources.
The weighing system

3. Weighing system maintenance

Weighing sensor is a precision electrical element, which needs to be kept away from dust, water and other substances. It is necessary to keep the sensor clean around, so some protective cover can be added to the sensor. At the same time, the weighing system needs to be recalibrated at intervals.

When checking the failure of the weighing system in the concrete mixing plant , we’d better adopt the elimination method to minimize the root cause of the problem.