SU1046619A1 - Balance having electromagnetic balancing - Google Patents

Abstract

1. BALANCES WITH ELECTROMAGNETIC EQUALIZATION containing a sensitive element with a load-bearing platform, with a suspension system and with a measuring coil located in the gap of the magnetic circuit and connected via an adder to the current source, the reference coil located in the same gap of the magnetic circuit, connected to the first output of the first switch , the control input of which and the control input of the switch are connected to the command unit, a reading device, a storage unit and an electrical compensation system in the form of a support O and controlled sensor 6mT1 compensating generators connected to a frequency subtractor, reversible counter, outputs of which are connected to a reading device, and connected to a reference oscillator count generator, code outputs of which are under: key to the code comparison circuit, phase comparator, output of which is connected to control the current input of the current key, the information input of which through the stabilizer is connected to the output of the storage unit, and the direct output - with an adder, characterized in that, in order to improve the accuracy and due to the possibility of installing zero in the process of long-term mass measurement, a second switch is inserted in them, the information inputs of the second switch are connected to the output of the subtractor, the control input is connected to the command unit, one pair of outputs of the second switch I is connected to the inputs of the memory (L block, and the other - to the inputs of the reversible counter, the outputs of the loop counter are connected to the inputs of the switch, the output of which is connected to one input of the comparator, the other input of which is connected to the code comparison, and the control input of the readout drive is connected to the command block. o 2. The balance according to claim 1, distinguishing 4 CD O) so that, in order to increase accuracy by providing a stable temperature mode of the magnetic system, an additional coil is inserted into them, connected through the first switch to the inverse of the current key output, moreover, the measuring, reference and additional coils are made with equal resistances 1. /

Description

The invention relates to weighing technology, in particular to weights, in which equilibration is achieved using electromagnetic forces. Known electromagnetic-digital scales, containing a sensitive element with a lifting device, a suspension system, a magnetoelectric transducer, a reference coil. a given mass, a command unit, an electromagnetic overlap device of the reference coil, an Uncompensating converter, and an electrical balance system 1. In the known weights, an increase in accuracy is achieved by calibrating the device before starting the measurement, however, the condition of the mandatory absence of the measured load on the load-lifting device in the calibration mode and manual calibration does not allow the use of scales of this type during continuous mass measurement (without removing the load during for a long time - weighing the substance flux on automated lines, measuring the mass in a physicochemical analysis}. The essence is an electromagnetic equilibrium balance containing a sensitive element with a lifting platform, a suspension system and a measuring coil located in the gap of the magnetic conductor and connected through an adder to a current source located in the same gap of the magnetic circuit the reference coil connected to the first output of the first the switch, the control input of which and the control input of the switch are connected to the command unit, the reading device, the storage unit and the electrical compensation system and as reference sensor and controllably non-compensation generator connected to the subtractor frequency down counter whose output is connected to the reference device, and a reference generator connected to the cyclic counter. code outputs of which are connected to a code comparison circuit, a phase comparator, the output of which is connected to the control input of the current key, whose information input is connected to the output of the storage unit through the stabilizer, and My output is connected to the adder C23. A disadvantage of the known device is that when measuring the mass for a long time, there is a decrease in the measurement accuracy associated with the complete impossibility of performing an automatic calibration of the scales in the presence of a measured load on the load-carrying cup. The aim of the invention is to improve the accuracy by providing the possibility of setting zero in the process of long-term mass measurement. The goal is achieved by the fact that in scales with electromagnetic balancing, containing a sensitive element with a lifting platform, with a suspension system and with a measuring coil located in the gap of the magnetic circuit and connected through an adder to a current source located in the same gap of the magnetic circuit, a reference coil connected to the first output of the first switch, the control input of which and the control input of the switch are connected to the command unit, a reading device, a storage unit and an electrical system trictive compensation in the form of a reference and sensor-controlled uncompensation of generators connected to a frequency subtractor, a reversible counter whose outputs are connected to a reading device, and connected to a reference cyclic counter generator, whose code outputs are connected to a code comparison circuit, a phase comparator whose output is connected A second key is connected to the control input of the current switch, the information input of which through the stabilizer is connected to the output of the storage unit and the direct output to the adder. a switch, the information inputs of the second switch are connected to the output of the frequency reading, the control input is connected to the command unit, one pair of outputs of the second switch is connected to the inputs of the storage unit, and the other to the inputs of the reversible counter, the output of the loop counter is connected to the inputs of the switch, the output which is connected to one input of the comparator, the other input of which is connected to the code comparison circuit, and the control input of the reading device is connected to the command unit. In addition, in order to improve accuracy by providing a stable temperature mode of the magnetic system, an additional coil is inserted in them, connected via a first switch to the inverse output of the current switch, and the measuring, reference, and additional coils are made with equal resistances. The drawing shows a structural diagram of the scales. The balance contains a sensitive element 1 with a lifting platform 2, stretching 3 and 4, a non-compensating transducer (sensor) 5 made in the form of a light source 6, a photodetector 7, a slit diaphragm 8 made in the frame of the measuring coil 9, a permanent magnet 10, a magnetowire 11, a reference coil 12 of known mass, a mechanical stroke limiter system consisting of stops 13–16, an electrical compensation system 17 consisting of a controllable generator 18, a reference generator 19, a frequency subtractor 20, a reversible counter 21, a circuit 22 with codes, cyclic counter 23 with intermediate output 24, pulse, which appears in the counter's distance, a certain number of NPs away from the state in which the overflow pulse, phase comparator 25, current switch 26 is output, and inverse output, the control input of which is connected to the output of the phase comparator, current regulator 27, reading device 28, first switch 29, second switch 30 ,. memory unit 31, logical switch 32, Tara current source 33, current adder 34, additional coil 35, command unit 36. Structurally sensitive element 1, load-bearing platform 2 and measuring coil 9 are rigidly fastened to each other and fixed on 3 and 4, forming the movable part of the balance. The operation of the scales is based on the compensation of the weight of the cargo P by the electromagnetic force F Py m g. F В „3„ 4t, / T, s / 1sG where m is the measured mass; g — free fall acceleration; B — induction in the gap of a constant magnet 10; . 3j, stabilizer current 27; ut is the duration of the current pulse T — the period of the pulse sequence, determined by the ratio of the capacitance of the cyclic counter 23 to the frequency 2 of the reference generator 19; Np - readings of the reversible counter 21; 10 - the capacity of the cyclic counter 23. The scales work as follows. When assembling and adjusting the weights, the mass of the HPA of coil 12 is preliminarily adjusted until the equality gSg Njj is reached, where Sp is the nominal sensitivity of the weights. From the start of the measurement, in the initial position, in the absence of a measurable load on load-lifting area 2, i.e at P 0, the command unit 36 sets the switch 29 and the switch 32 to position A, and the switch 30 moves to the lower position, connecting the outputs of the subtractor 20 frequencies to the inputs of the reversing counter 21, From the manually adjustable source 33 of the tare current through the current adder 34 to the measuring Coil 9 is supplied with a current T of initial calibration that compensates for the weight of the movable part of the balance, the tare weight and the drift zero. At the same time, the slit aperture 8 is in the zero position, the signals from the outputs of the non-compensation converter 5, the subtractor 20 frequencies, the reversing one, the counter 21 are equal to zero. On the reading device. 28 is set to zero. . The coil 12 through the switch 29 and the inverse output of the current switch 26 receives the current JQ of the current regulator 27. The coil 12 is in the extreme upper position, pressed against the stops 14 and 16 by the force FP ВРдЗц Рд m ,, g, where PO is the length of the drive in coil a2; Rd is the weight of the coil 12. In contrast to the known device, in this case, an additional source of current is not required. allows you to simplify the design of the scales, as well as provide a constant thermal regime of the magnetic system. After balancing the tare, the weight of the movable part and the drift correction, the nud is adjusted according to the signal. The PO is lowered onto the stops 13 and 15. Thus, the calibration force PQ is applied to the sensitive element 1. Simultaneously with the supply of P, the output of the phase comparator 25, due to the switching of the switch 32, impulses with relative duration Atp / T N / o appear. This leads to the creation of a compensating force F}, where in and Jg are, respectively, induction in the gap of the magnetic system and the current stabilizer current at the time of the calibration. 31 JHOM where at B BHOM nom are B and 3 values corresponding to the nominal sensitivity, produced compensating force. The movable part of the balance remains in the zero position, the state of the storage unit changes. This eliminates the transient processes of balancing the weight of the PO, which occur in the known device, thereby increasing the speed of the device action. If there is a sensitivity error (Ffi PO) f which may be caused by instability B, J or inclination of the balance, which is equivalent to a change in the component of acceleration of gravity along the axis of sensitivity, the movable part of the balance shifts from.

neutral position. At the output of the non-compensating converter 5, a signal appears, the sign of which depends on the sensitivity error. The generators 18 and 19 are mismatched, and the difference frequency signal a appears at the outputs of the frequency subtractor 20. The differential frequency pulses are counted in a storage unit 31, which adjusts the current JQ of the stabilizer 27 until equality

Po-- o () fi) and)

where lr is the change in the component of accelerating the force of gravity along the sensitivity axis;

AD is the current increment of the current stabilizer 27 during the instrument calibration process. The mobile part returns to its original state, indicating that the calibration is complete. The value of the stabilizer current 27 at the end of the calibration cycle is equal to

er; l; ± le t (± d) ((.2)

At the end of the calibration, the command unit 36 switches the switch 30 to the lower position, and the logical switch 32 and the switch 29 sets it to position A. This will lock the memory unit 31 and release the lock from the reversing

Counter 21. Coil 12 occupies an extreme position. Scales are prepared for measurement.

When a load with a measured mass t is established, on the platform 2 the movable part of the balance shifts downwards by. the output of the transducer 5. a mismatch signal U appears, dependent on PX () / oscillators 18 and 19 are mismatched, at the outputs

The subtractor 20 is the signal of the difference frequency j-, the reversible counter 21 counts the pulses that have arrived during the balancing process. As the number of pulses in the reverse counter 21 pocTai increases, the residence time of the phase comparator 25 in a single state is determined by the difference between the instants of cyclic counter 23 overflow pulses through the logical switch 32 and pulses from the output of the circuit 22 coincidence. This leads to an increase in the duration of l ± and an increase in the compensating current Ojj. The process of changing the current Ll continues as long as the produced compensating force

 F, j does not balance P. After equilibration, the movable part of the balance returns to its original state, the raion at the outputs of the subtractor 20 often

becomes zero, and the reversing counter 21 stops, memorizes the dialed code pattern

Nx / r) "X / BPn OK (I

Substituting the value 0 from (2) into (3), we get

.. 5g.

 () the result is not dependent on the sensitivity error.

A feature of the scale is the ability to perform subsequent calibrations of the instrument without removing the load from the load receiving platform. Based on the possible Rate of change of sensitivity error, the command unit 36 is given calibration frequencies.

Let the code combination be written in the reversible counter 21K.

N () r. (s ± jsJ,

X

where L5 and j-dS / Sp are, respectively, absolute and relative error of sensitivity to the time of calibration caused by a change in B, Ed and nd in the measurement process m. Calibration, performed by a signal from the command unit 36, is similar to the calibration described above without the load t on the load carrying area 2. The difference is that in the calibration mode, in addition to the calibration force PQ, the sensitive element 1 is acted upon by the force R. The duration of a single pulse of the phase comparator 25 is defined as

() / T- (x) °. which leads to the creation of a compensating force Fp (N |, + NoJ-ro, where B and, J are B and JQ values at the time of the calibration.

Because of the presence of sensitivity error j, the force developed

 () something leads to displacement of the moving part of the balance from the neutral position, misalignment of the generators 18 and 19. The memory 31 begins to change the current of the current stabilizer 27 until a compensating force Ppc returns the moving part of the balance to the neutral position. This indicates the fulfillment of equality

f) (V) / - ° K%); () (four)

The current value of the stabilizer 27 at the end of the calibration is

U -h.) - K -%) (

. ° K)

It should be noted that if, i.e. Nj SQ m state. the storage unit 31 in the calibration mode does not change.

In case of a subsequent change in the reversible counter 21, the code will be written

  ,, (

(B)

 t

hk

 about rt

Substituted the current value (in (6), we get

N - (-) K) n NX

; XK -%) (i).

- ..

 K: ScC% / 5o% -)% / (% / v) The relative sensitivity error after calibration has

view and,} I

.. ,, (

J

From (7), it can be seen that the efficiency of calibration depends on the ratio of the measured and the reference mass. Thus, with m, m (, incomplete correction J can be taken into account when choosing the calibration frequency. If necessary, measurement accuracy can be performed using a signal from the command unit to carry out a series of calibrations, in this case the indication of the reading instrument is extinguished during the calibration and only allowed the end of the last cycle. The relative sensitivity error for the calibration steps has

Ггп / / т, П j (ij).

So prk

view

 1st /% a.

tn mp at the end of the second calibration ° end of the third jj j / in, etc. .

The proposed implementation of the weights allows to significantly improve the measurement accuracy by fully automating the calibration mode indifferent to the weighing character (both for one-time and long-term weighing), which significantly expands the functionality of the scales. In the known device for automating calibration, it is possible5 for only one-time weighing, where it is easy to find time for an error — in moments of no load at the receiving platform. In addition, in the known device, the condition for correct calibration is preliminary correction of additive error; in the proposed device, the result of calibration does not depend on. additive error.

In the proposed balance in the pauses of the current pulse in the meter, coil 9, the current stabilizer 27 current flows either into the reference coil 12 (in measurement mode) or into the additional coil 35 (in calibration mode), and the minimum value is the current value in the reference coil 12 should be sufficient to create an electromagnetic force greater than the weight of the PQ. This makes it possible to refuse additional

current source. Since the resistances of the laziness of the coils 9,12, and 35 are equal, the total power released in the Katoumk is constant, which leads to

Q is the constant temperature of the air gap of the magnetic system.

j I a {If

Yjv

f f

Is.

Claims (2)

1. ELECTROMAGNETIC SCALES By balancing, containing a sensitive element with a load pad, with a suspension system and with a measuring coil located in the gap of the magnetic circuit and connected through an adder to a current source located in the same gap of the magnetic circuit of the reference coil connected to the first output of the first switch, the control input of which and the control input of the switch is connected to the command unit, a reading device, a storage unit, and an electric compensation system in the form of a __ • reference and controlled sensor ompensatsii generators connected to the subtractor frequency down counter, the outputs of which are connected to a reading device, and a reference generator connected to the cyclic counter, which outputs a code; Keys to the comparison circuit codes the Optional _(Izovogo comparator whose output .Connect to the control input of the current key information input via a stabilizer connected to the output of the storage unit, and a direct output - to an adder, characterized in that, in order to increase the accuracy of due to the possibility of setting zero during a long measurement, mass, a second switch is introduced into them, and the information inputs of the second switch are connected to the output of the frequency subtractor, the control input is connected to the command at the unit, one pair of outputs of the second switch is connected to the inputs of the storage unit, and the other to the inputs of the reversible counter, the outputs of the cyclic counter are connected to the inputs of the torus, the output of which is connected to one input of the comparator, the other input of which is connected to the code comparison circuit, and the control the input of the readout drive is connected to the command unit. 2. The balance according to claim 1, characterized in that, in order to increase accuracy by ensuring a stable temperature regime of the magnetic system, an additional coil is introduced in them, connected through the first switch to the inverse output of the current switch, and the measurement, reference and additional coils, made with resistance. equal to /