The working principle of belt scale

                                            The working principle of belt scale

First, the composition of belt scale

General framework by weighing, weighing sensor, speed sensor and display instrument and so on four parts

Second, the control principle of belt scale

1, the scale for quantitative feeding of material

Continuous feeding, feeding process for belt feeder will come from the user to bin or other feeding equipment of conveying and through the weighing bridge test weight, at the same time, installed in the tail wheel speed sensor was carried out on the belt speed detection. By measuring the weight of the signal and speed signal into together MT3105P integrator differential processing and display in tons per hour as the unit of instantaneous flow rate, and the corresponding signal according to the deviation from the size of the output value (PID) signal, speed changing motor speed by frequency converter to change quantificationally, to that of the specified period, so as to complete a constant feed flow rate control. From weighing principle, the instantaneous flow rate measured by the electronic belt scale materials depends on the size of the two parameters, namely the instantaneous flow rate is equal to the carrying on of the weighing sensor material load value q (kg/m) and speed measuring sensor measurement value v belt speed (m/s) when multiplied two parameters, i.e., w (t) = qv visible and speed sensor of measuring accuracy and stability and the measurement precision and stability of the weighing sensor is equally important. The general improvement in the accuracy of weighing sensor to several per, and the accuracy of the speed sensor is mostly in a few parts per thousand, so to improve the precision speed sensor is one of the ways to improve accuracy of electronic belt scale system effectively.

2, start feeding machine:

In site operation box to press the start button 1 s b, 1 1 ka3 relay ka1, and at the same time, the inverter start signal is closed, the feeder and motor fan began to run, run indicator 1 hl2 on (batching scale fault when the lights flashing), through the speed control knob 1 rp make inverter output current and the motor speed changes, and in the process of running found wandering should press the stop button sb2 1 belt adjustment, also can adjust the phone is switched on. Central boot tell commonly switch hit central location, panel must be ready lights on, or on behalf of the central unbootable or damage of the lamp.

Three, parameter setting and calibration of the weighing feeder

1, instrument calibration parameters:

Running belt to stabilize after period of time, can the MT3105 instrument set parameters, such as losing the instrument decimal point position, unit scale, capacity, sensors, capacity and sensitivity, the belt length parameters, such as a week. First time use need to input the original parameters, in normal use generally don't need to change at will.

2, the calibration of the weighing feeder:

Acquire the test cycle, then zero calibration, after the zero stability interval can be standard, divided into physical calibration interval, chain code, hanging code calibration methods, such as the Ramsey dedicated AUTO - MAT (automatic) material calibration software, can automatically correct belt scale interval value, after N times calibration, make according to weighing measurement standard, can be put into normal weighing measuring, the cumulative.
4、 Causes of zero drift and interval drift
Zero drift is generally related to the conveying system. The causes of zero drift are as follows:
a. Dust and materials accumulated on the weighing bridge.
b. Materials and sundries are stuck in the weighing bridge.
c. There is sticky material on the belt conveyor.
d. Uneven belt tension.
e. Due to the temperature characteristics of materials and the long-term use of the belt, the belt is elongated.
f. Failure of electronic measuring element.
g. Severe overload of load sensor.
Causes of interval drift
① Conveyor belt tension change
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② Sliding of speed measuring drum or change of its diameter
③ Change of belt speed
④ Heavy overload of load cell
⑤ Failure of electronic components
⑥ Severe deformation of scale frame
5、 Fault analysis and judgment
1. Load cell
There are two common forms of load cells: pressure and tension. ± exc is the excitation terminal, and this voltage is provided by the instrument, which should be 10VDC ± 5%, ± Sen is the compensation terminal, and this voltage is consistent with ± exc. ± sig is the signal output terminal, and the size should be a value between 0 and 20mV. In normal use, the output of the belt under no load shall not exceed 15MV, and increases with the increase of load. Therefore, the most direct way to judge the quality of the load cell is to measure the DC voltage of the multimeter. First, ensure that ± exc is 10VDC ± 5%. If there is no such voltage, check the instrument; If there are multiple sensors, remove the signal terminal and measure them separately to ensure that the output of each sensor is 0-20mv, and the value increases with the increase of load. In addition to voltage judgment, it can also be judged by measuring the input and output resistance. The specific method is as follows: ± exc (± SEN) is 400 Ω± 5 Ω, ± sig is 350 Ω± 5 Ω, and the shielded wire and any terminal are greater than 5000m Ω.
2. Speed sensor
The speed sensor is actually a stepping motor, and its output signal frequency is directly proportional to the number of revolutions of the input shaft. Therefore, there are still two methods when checking with a multimeter: resistance measurement method: use the resistance gear of 200 Ω, and the resistance measurement should be 135 Ω± 2 Ω. Voltage measurement method: use the gear of 20vac to measure the voltage. When the conveyor stops, the voltage is zero. When the conveyor operates normally, the voltage is a value of 3-10vac. The higher the speed, the greater the value. During routine maintenance, the connecting shaft sleeve between the speed sensor and the speed measuring drum should be cleaned. The shaft sleeve couples the two shafts together through the jacking wire. Therefore, the loosening or falling off of the jacking wire will affect the normal speed measurement and cause the inaccurate voltage value measured by us.
3. Appearance
Detect the function of each signal. If a fault is found, it will appear on the display screen at any time. When the fault disappears, the fault display must be reset to remove the fault of the instrument. Common faults of the instrument include: load cell fault, speed sensor fault, division error, etc. if the instrument crashes (this is a rare phenomenon, but sometimes it will inevitably occur), cold start the instrument to restore all data to the factory setting data. The instrument can be used normally only after it is reset and calibrated.
6、 Maintenance of electronic belt scale
With only a small amount of maintenance, the electronic belt scale system can achieve satisfactory use effect in a few weeks. Even if the newly installed first calibration, it can be calibrated and put into use by simply carrying out zero calibration and interval calibration.
1. Clean regularly to prevent the scale volume from accumulating ash, resulting in inaccurate weighing.
2. Regularly check whether there are materials or foreign matters stuck in the moving part of the belt scale. The specific inspection positions include: the middle position between the idler and the conveyor frame, and the cross beam between the scale frame and the scale body.
3. If the belt deviates, it shall be adjusted regularly to prevent inaccurate measurement.
4. Do not impact the scale body and sensor with external force. It is strictly prohibited for maintenance personnel to stand on the belt scale or operate other equipment during maintenance.
5. During equipment overhaul, do not carry out electric welding, gas cutting and other operations on the scale body.
6. The signal cable shall not be cross arranged with the power cable during laying or use to prevent interference.
7. The instrument shall be reliably grounded with independent power supply.
8. Ensure that the weighing idler and the idler in the weighing area can operate freely, otherwise replace it.
9. The speed measuring drum shall be cleaned regularly to prevent sticking.
10. The bearing seat of the speed measuring drum shall be lubricated regularly.
11. Regularly check the jacking wire at the shaft sleeve of the speed sensor to prevent loosening or falling off.