SU1525475A1 - Device for measuring mass and controlling flow of loose material - Google Patents

Abstract

The invention relates to a weight measuring technique and can be used to measure the mass of moving objects or the mass of cargo transported by conveyors. The invention improves measurement accuracy by compensating for the zero drift of the weight sensor and increasing the accuracy of the analog-digital conversion. The signal from the weight sensor 1 is fed to the information input of the specialized analog-frequency converter 2, from whose information output during the time T _U1 and T _{U2 the} frequency signal passes to the third counter of timer 5. Forming the same measurement time intervals T _U1 and T _{U2 is} carried out first the timer counter 5, which is filled with pulses of the generator 4 under the control of the microprocessor computing unit 7. Moreover, to compensate for the component of the measurement error due to the zero drift of the weight sensor 1, measuring sig The weight sensor 1 in the time intervals T _U1 and T _{U2 is} produced at different polarities of the supply voltage of the load cells of the weight sensor 1. For this, the device is equipped with a trigger 3, which is switched by pulses from the microprocessor computing unit 7 and changes the signal level at the control input of the converter 2 analog-frequency, which also generates the supply voltage for the load cells of the weight sensor 1. The second counter of timer 5 forms the time interval Τ (between T _U1 and T _U2 ), during which the signal of the weight sensor 1 stops measuring for the period of switching the polarity of the voltage of the load cells. The code N _U , recorded during the measurement time T _U1 + T _U2 in the third counter of timer 5, proportional to the signal from the weight sensor 1, is further processed in the microprocessor computing unit 7. 2 Il.

Description

The invention relates to a weighing equipment and can be used to measure the mass of moving objects, the mass of cargo transported by belt or other conveyors, in continuous or batch metering devices with analogue weight sensors.

The purpose of the invention is to increase the measurement accuracy by increasing the accuracy of the analog-digital conversion of the weight sensor signal.

FIG. 1 shows a diagram of the proposed device; in fig. 2 - time diagrams of his work.

A device for measuring mass and controlling the flow of bulk materials (Fig. 1) contains an analogue weight sensor 1, a specialized converter 2 analogue - frequency, trigger 3, generator D of rectangular pulses, timer 5, containing three pulse counters, inverter 6, microprocessor computing unit 7, provided with an I / O interface 8, a weighing result indicator 9, actuators 10 for controlling the flow of bulk materials and a pulse velocity sensor 11 connected via the I / O interface 8 to one input of the microprocessor computing unit 7. The output of weight sensor 1 connected to data input transducer 2 analogue - frequency, a first output of which is connected to the data input of the third timer counter 5, the second output - to an input of Nutrition datchi5

0

five

0

five

0

five

1, and the information inputs of the first and second counters of the timer 5 and the second input of the microprocessor computing unit 7 (via the input-output interface 8) are connected to the output of the square pulse generator A. The enabling inputs of the first and second counters of the timer 5 are connected to the source of the reference voltage, and the enabling input of the third counter of the timer 5 is connected via inverter 6 to the output of the first counter of timer 5 and via the input-output interface 8 to the third input of the microprocessor computing unit 7. Fourth input microprocessor computing unit 7 through the input-output interface 8 is connected to the output of the second counter of timer 5, and the first output of the microprocessor computing unit 7 through the input-output interface 8 is connected to the counting input of the trigger 3, one of the outputs of which is connected to the control input of the converter analog - frequency. The second and third outputs of the microprocessor computing unit 7 through the I / O interface 8 are connected respectively to the Read input and the Record entry of the timer 5, and the data bus (11Shch) and the address bus (ShA) of the microprocessor computing unit 7 are connected to the corresponding I / O interface 8 timer buses 5. Indicator 9 through the interface 8 input-output connected to the fourth output of the microprocessor unit 7, the fifth output of which through the interface 8 in 15

yes output connected executive

mechanisms 10.

Each counter of timer 5 is a 16-count countdown registrar, i.e. working only on the subtraction. The microprocessor computing unit 7 contains a microprocessor (MP), a permanent memory (ROM), random access memory (RAM) and other elements and is intended to control the weighing and dosing process, as well as arithmetic operations.

All units of the proposed device are standard and commercially available. For example, as the trigger 3, you can use the K155TV1 chip, timer 5 - the K58VI53 chip. As a source of supports

For a voltage U, any device voltage corresponding to 1 can be used.

The device works as follows.

When measuring the mass of the load moved by a belt conveyor, i.e. when the device operates pulses from

The presence in the expression (2) of the ± sign is due to the fact that at the second output of the specialized converter 2 analogue-frequency, the supply voltage for the load cells of the weight sensor 1 is formed. Moreover, the polarity of the supply voltage supplied from the analogue converter — the frequency to the strain gauges depends on the signal level on the fy (t) proportional to the speed of the conveyor belt, through the input-output interface 8 goes to the microprocessor computing unit 7, which, by the duration of the period T, the arrival of pulses is determined by the SP

The reference input of the transducer 2 is ana-speed sensor (Fig. 2) with frequency. If this signal is 1, then the voltage level of the load cells of one polarity, if O, is different.

Direct measurement of the signal, weight sensor 1 is preceded by setting timer 5. To initialize timer 5 from microprocessor computing unit 7, a set of control words must be entered into timer 5, where h is the segment of the path, passing 40 Gives zero the mode and initial knowledge of the conveyor belt speed sensor 11 generates another pulse.

The operation of the device consists in repeated measurement in the range of the signal values of the sensor 1 weight, the calculation of the mass of the load M; relocatable

velocity v is made on interval t

wed; h / Tc .;

C.I

tape movement

(one)

45

each individual counter. To do this, at time t, the address of the first counter of timer 5 is set through the input-output interface 8 from the microprocessor computing unit 7. Then from the third output of the microprocessor computing unit 7 via the input-output interface 8 to the input Record timer 5 (communication line 14) a zero-polarity pulse is applied, by which the SM of the microprocessor computing unit 7, through the I / O interface 8, writes the initial code n to the first counter of timer 5. The next command, the microprocessor computing unit 7, sets the address of the third counter of timer 5 on the I / C and searches the microprocessor unit 7 for the check-in during T

J.; and finally

determining the resulting mass of cargo Mp moved by the conveyor during the weighing time o.

The signal and, from the weight sensor 1, proportional to the mass of the load in the measurement area of the conveyor, is fed to the information input of the converter 2 analogue-frequency. On the first (informational) output; formaker 2 analogue — the frequency is produced by the signal u2 with the frequency

() 2fo T

X o

 K, (Ugt.1, J,

(2)

with

where f.

f,:

0

k. L a converter transducer 2 analogue - frequency; coefficient of proportionality; useful information signal of the weight sensor 1; the value of the drift zero sensor 1

weight or magnitude of the unbalance of the bridge strain gauges.

The presence in the expression (2) of the ± sign is due to the fact that at the second output of the specialized converter 2 analogue-frequency, the supply voltage for the load cells of the weight sensor 1 is formed. Moreover, the polarity of the supply voltage supplied from the analogue converter — the frequency on the strain gauge depends on the signal level on the direct measurement of the weight sensor 1 signal is preceded by setting timer 5. To initialize timer 5 from the microprocessor computing unit 7, it must be entered in timer 5, a set of control words specifying the zero mode and initial values

each individual counter. To do this, at time t, the address of the first counter of timer 5 is set through the input-output interface 8 from the microprocessor computing unit 7. Then from the third output of the microprocessor computing unit 7 via the input-output interface 8 to the input Record timer 5 (communication line 14) a zero-polarity pulse is applied, by which the SM of the microprocessor computing unit 7, through the I / O interface 8, writes the initial code n to the first counter of timer 5. The next command, the microprocessor computing unit 7, sets the address of the third counter of timer 5 on the AE, and with the search for microprocessor unit 7 through the input-output interface 8, the initial code FFFF ,, -) is written to the third counter of the timer (units in all counters) . Writing into the first counter of timer 5 of the initial code P) in the presence of 1 at the enabling input PJ opens the first counter of timer 5, and the pulses from the generator A of rectangular pulses with a frequency f will start to pass to the first counter of timer 5, decreasing its value, i.e. the first measurement interval ty signal of the weight sensor 1. The pulses from the generator 4 also arrive via the communication line 17 continuously via the input-output interface 8 to the microprocessor computing unit 7, synchronizing the operation of all its nodes.

The value of the initial code n is chosen such that, at a frequency f of the generator 4 rectangular pulses, to provide the required duration of the measurement interval t y, (for example.

-U.1

0.1 s)

HI fr tu.i (3)

After entering the initial code hi into the first counter of timer 5 (the time t signal at output Q (i timer 5 becomes equal to zero, therefore, the enable input P of the third counter of timer 5 through the inverter 6 gives a signal and a high level (Fig. 2) allowing Thereby, the passage of pulses from converter 2 is analogous to the frequency on the third counter of timer 5, i.e. the counting begins in the reverse code of the number of pulses from converter 2 to analogue to frequency.

After the first counter of timer 5 receives a number of pulses equal to a given n (time t), the output Q of timer 5 produces a single interrupt signal, which

through the input-output interface 8 enters the microprocessor computing unit 7 (communication line 15). At the same time, the first counter of timer 5 is automatically locked and, through inverter 6, a low level at the enable input P blocks the count of the third counter of timer 5. At the same time, the third counter of timer 5 records the value of the N code proportional to the signal of the weight sensor 1 in the measurement interval

neither t

0

N, tu., - f t., Kf, U,

tu, K (U., 1, .J,

Q with

n

five

d

0

five

five

where UQ, is the useful information signal of the weight sensor 1 in the time measurement interval

tu, - At the interrupt signal (on line

communication 15) the microprocessor computing unit 7 exposes through the interface 8 input-output address to the address of the second counter of the timer 5, and to the reference data - the initial code n of the counter. Then through the interface 8 input-output microprocessor computing unit 7 /

line 14) sends a signal to the timer 5 Record, according to which the second code of the timer 5 with the SM rewrites the initial code n and opens the second counter timer 5 (for the enable input P, high signal level) for counting. Then, from the first output of the microprocessor computing unit 7 (communication line 12), through the input-output interface 8, a pulse arrives at the counting input of trigger 3, tilting trigger 3 to the opposite state (in our example, one). This leads to a change in the opposite value of the polarity of the supply voltage supplied from the converter 2 analog-frequency to the strain gauges of the weight sensor 1. The code value n is chosen so that at the received frequency f of the generator of 4 square-wave pulses, the measurement cycle is interrupted for a time sufficient to stop all transients in the weight sensor 1 and the analog-to-frequency converter caused by switching the voltage of the strain gauge voltage - fork weight sensor I (20 ms).

.(five)

At time t (the second counter of timer 5 received a number of pulses equal to the given n), the second counter of timer 5 is automatically locked, and the output Q of timer 5 produces a single interrupt signal, which via communication line 16 enters microprocessor interface 8 of I / O computational unit 7. According to the interrupt signal, the microprocessor computational unit 7, through the input-output interface 8, sets the address of the first counter of timer 5 to the AE, and the initial code of the first counter in the SM. Then, using the Record signal, the timer enters 5 Interface I / O interface 8 from microprocessor computing unit 7, code n is rewritten into the first counter of the SM timer 5, and the first counter of timer 5 is opened for counting (the formation of the second measurement interval tu begins); At the same time, the signal at the output Q of timer 5 becomes zero and through the inverter 6, the permitting input Pg of the third counter of timer 5 is given an I single signal, which excites the third counter of timer 5, i.e. the measurement of the output signal of the converter 2 analogue — frequency, continues

After the time t y ,, n, / fp (ty,), the first counter of timer 5 is zeroed (it is automatically locked) and at the output Q time - ipa 5 a single interrupt signal is generated, which through the communication line 15 through interface 8 I / O enters microprocessor computing block 7 / moment i.,

The high signal level at output Q gj of timer 5 through inverter 6 blocks the third counter of timer 5, i.e. suspends his work. In this case, a Mi code will be fixed in the counter, which is proportional to the signal of the weight sensor 1

Nc N + M, (6) where NJ t, f, t (j 1: „(ICM) is the number of pulses received from converter 2 analogue - frequency per Input of the third counter of timer 5 in the interval

and

}

- useful informational sig

the weight of the sensor I in the measurement time interval tm.

NU tu., Cr (Ugi + ICM) + + tui K Ug, - 1,) ,, (Ug, -H -b) (7)

From the expression (7) it follows that measuring the signal of the weight sensor I for a time t, + t c 2tu, switching the polarity of the power supply voltage of the sensor, eliminates the effect of zero drift (bridge imbalance) of the strain sensors on the value N.

According to the interrupt signal (time tj -) -, received via the input-output interface 8 to the third input of the microprocessor computing unit 7 from the output QJ of the timer 5, the microprocessor computing unit 7 through the input-output interface 8 sets the address of the third counter of timer 5 to the I / O , and whether, Q

0 5

about

five

The communication 13 sprinkles a zero pulse. Reading to the input of timer 5. At the same time, the contents of the third counter (N) of the timer: 5 over the SM are written into the RAM of the microprocessor computing unit 7 (communication line 12), via the I / O interface 8 the counting input of trigger 3 receives a pulse, tilting trigger 3 to the opposite state (in the diagram, to zero), which causes a change in the polarity of the supply voltage of the load cell of the I-sensor.

The time remaining until tg (shaded in the diagram) is used by the microprocessor computing unit 7 for processing the obtained measurement results of the signal from the weight sensor 1 and preparing for a new measurement cycle T, i.e. in the microprocessor computing unit 7, the product Nt (Lc) is calculated and stored in a separate memory cell of the RAM, this product is summed with the value previously obtained in the previous measurement.

At time t, a new, similar to that considered, cycle T of measuring and processing the signal of the weight sensor 1 begins.

At time t (Fig. 2), through the input-output interface 8, a pulse is received from the speed sensor 11 via the input of the microprocessor computing unit 7, which calculates the average speed Vjp in the microprocessor computing unit 7; and the multiplication value (.p /, on the accumulated

the sum of

j i

Ny-ty, where m is the number of, the number of measurement cycles T, laid down in the time period.

I As a result, the mass of the cargo M; conveyed by time and

is defined as m

n; K-Vcp;

.

(eight)

where K is the conversion factor.

The resulting value of M; stored in the RAM of the microprocessor computing unit 7 for subsequent summation by partial masses.

Since the summation of the computational values of the masses is performed periodically with a frequency, the resulting weight of the load: "displaced by the conveyor during the weighing time J) is equal to

Where

eleven

P m Mr K lVcp pj, - t, (9)

- the number of pulses of the speed sensor 11 received at the microprocessor computing input

f block 7 in time T).

-

The result of calculating the mass of cargo Mp from the microprocessor computing unit 7 via the input-output interface 8 enters the weighing result indicator, according to which you can judge the mass of the load moved by the conveyor, or can flow to the actuators 10 to control the dosing process of the conveyed conveyor

material.

Claims (1)

Thus, the proposed device makes it possible to increase the accuracy of measuring the mass of a load transported by a conveyor by eliminating the component measurement error due to the zero drift of the weight sensor, the possibility of placing the analog signal converter in the part directly at the weight sensor by connecting it to a timer via a long line , introducing other characteristics into the measurement process. The use of the device in continuous dispensers, along with an increase in viscosity, the measurement reduces the permissible basic error and loss of the dosage material during preparation of the process, reduces the time to reach the steady state. Invention Formula Device for measuring mass and controlling the flow of bulk material 12 0 five 25 30 0 a la containing a microprocessor computing unit with an indicator and an output for connecting to the control actuator, an analog weight sensor and a speed sensor connected to the first input of the computing unit, characterized in that, in order to improve the accuracy, an analog-frequency converter is inserted into it, trigger, timer with three pulse counters, square pulse generator, inverter and reference voltage source, with the output of the square pulse generator connected to the second input of the calculator The output of the first pulse counter is connected to the third input of the computing unit and through the inverter to the enable input of the third pulse counter, the information input of which is connected to the first output of the first and second pulse counters, enabling inputs of which are connected to the reference voltage source. the analog converter is the frequency, the first Exit of the computing unit is connected to the counting input of a trigger, one of the outputs of which is connected to the control input of the converter A log is the frequency, the information input of which is connected to the output of the weight sensor, the second and third outputs of the computing unit are connected respectively to the input. Read and Write the timer, the data bus and the address bus of which are connected to the corresponding buses of the computing unit, the fourth input is connected to the code. second pulse counter. 40