SU763690A1 - Level measuring device - Google Patents

Description

The invention relates to a measurement technique, in particular, to devices for periodically measuring the level in industrial containers filled with an aggressive and non-aggressive, liquid, as well as bulk material. There are known devices for measuring levels in which, as a parameter characterizing the filling levels of a container, the time interval between the moment the probe begins to move and the moment when the probe meets the filling material, which contains a probe lowered to the surface of the material under test, is controlled by the drum. control circuit. The counting pulses from the generator through the coincidence circuit, the counter and the digital-to-analog converter are fed to the indicating and recording device 1. The disadvantage of this device is that since the frequency of the pulse generator is not related to the actual speed of the probe down, the measurement accuracy will change when voltage and frequency fluctuations occur in an electrical network and, it will accumulate as the probe is lowered into the capacitance. The closest to the proposed device according to the technical essence is a level gauge containing a probe on a cable wound on a drum with a one meter turn length, electric drum drive, signal flags in the amount of usually ten pieces fastened on the drum and passing as the drum rotates through a contactless sensor, a meter for detecting the level, and a control circuit 2. A disadvantage of the known device is insufficient measurement accuracy. The aim of the invention is to improve the measurement accuracy. The goal is achieved by the fact that the device is equipped with a counter for the number of fractions of a drum’s turn, a time relay and a pulse generator at a stable frequency, when the output of the non-contact drum rotation sensor is connected to the input, a reset counter for the drum’s turn is connected to the input and the counting input of the rotational speed counter drum, and the output of the generator 3 pulses of a stable frequency is connected to the counting input of the counter of the shares of the 6afra bar. FIG. 1 shows a block diagram of a level gauge; in fig. 2 shows a specific implementation of an equalization control circuit. The device consists of a probe 1 on a cable 2, wound with a coil length of 1 m, on drum 3 connected to an electric drive 4. Signal flag 5 is fixed on the cheek of the drum, under which there is a contactless sensor 6 of the drum speed. The probe in the initial position by means of the strip 7 acts on the limit switch 8. The probe, the electric drive and the limit switch are electrically connected to the control circuit 9 containing the sensor 10 commands, control unit II, time relay 12 and generator 13 of stable frequency pulses. For recording the readings, there is a block of 14 readings, including a 15 meter counter and a 16 meter meter counter, not connected to each other, but electrically connected to the control circuit 9. The 6 rpm sensor is electrically connected to the reset input of the meter 16 meter and through the relay 2 contacts time delayed with a counter with a counter input of 15 meters. The magnitude of the required preliminary elevation of the probe in the initial position above the monitored capacity is determined based on two boundary conditions: the indicated elevation of the probe must not be less than the distance that the probe travels during the acceleration of the electric drive to the nominal speed; . The elevation of the probe should be no greater than the difference between the circumference of the circle described by the signal flag and the radius of winding of the cable on the drum, and the width of the signal flag. The prerequisite for fixing the signal flag on the drum cheek in order to clearly fix the level zero point is that the arc length of the circle traversed by the signal flag from the initial state before meeting the drum speed sensor, reduced to the winding radius of the cable be equal to the elevation of the probe above the controlled capacity. The position of the flag on the neck of the Barbara is determined by the angle on which the drum turns while moving the signal flag from the initial position to an encounter with the drum speed sensor equal to | b (degree). The device works as follows. The signal from the sensor 10 commands (start button or software device) control unit 11 resets the counters 15 and 16 of the previous measurement Ursv, turns on the time relay 12 and turns on the electric drive 4 to soften the cable 2, which lowers the probe 1. When the drum 3 rotates, the signal flag 5 acts on the drum speed sensor 6. This effect occurs at the moment when the probe base passes the level, i.e. upper cut-off controlled capacity. By the time the probe reaches the base of the reference level, the transient process of the electric drive (acceleration) has ended, and the probe descends at a uniform rate. On the pulse signal of sensor 6, the control unit 11 connects a generator of 13 pulses of stable frequency to a counter of 16 parts of meter, the level reading in the monitored capacitance begins. The first pulse signal of sensor 6, from which the level begins (a fraction of a meter) is not detected by a 15 meter counter, since the time delay relay 12 is chosen equal to the time interval between the start of the drum rotation and any moment between the first and second passes of the signal flag through the pulse sensor. This prevents the meter from being recorded as an extra meter, and the level reading begins with a fraction of a meter. When the signal flag passes the sensor 6 again (the probe from the base of the level has lowered exactly 1 m), the pulse signal from the sensor resets the counter of 16 fractions of a meter, starts it up again and records the unit in the meter 15 meters. Therefore, if the frequency of the pulse generator 13 turned out to be mismatched with the actual probe lowering speed for one reason or another, then the error in level measurement due to this discrepancy will not accumulate over the entire measured height and will not exceed the accumulated one during the drum rotation (during the passage of one meter). When a probe reaches the surface of a material in a controlled capacitance, a control signal is received (for example, from a relay in the probe circuit, if the material is electrically conductive, or any other sensor that detects when the probe reaches the "Controlled medium") The control circuit on this signal stops on both counters and issues a command (with a time delay for ending the transients in the electric drive) on the reverse

electric drive. The electric drive with the drum begins to raise the probe; the counters do not work, but they keep the readings.

Upon reaching the initial position, the probe through the bar 7 acts on the final

switch 8, at the signal of which the control circuit turns off the electric drive.

The device is ready for a new measurement cycle.

The specific implementation of the control circuit of the gage is shown in the FNG. 2. The above control scheme is made using contact equipment. Possible implementation of the control circuit and contactless logic elements.

When the control button 1 is pressed, the relay 2 is turned on, which with its contacts 3 resets the meter readings of 5 meters and contacts 4 to reset the meter readings of meters 6, and also contacts 7 switches on the intermediate start relay 8. Relay 8 through its own contacts 9 stanis to self-blocking (contacts 7 of relay 2 are bypassed). When the relay 8 is turned on by means of the contacts 10, the relay 11 also delays the counting time of meters and by means of contacts 12 turns on the coil 13 of the reversible magnetic needle. The latter includes an electric drive to lower the probe down. In addition, when the relay 8 is turned on by its pins 14 and 15, the power supply circuit of the counting inrush relay 16 and the automatic reset circuit of the meter 5 parts are prepared.

When the drum of the equalizer rotates during the first exposure of the signal flagA: on the sensor of the number of revolutions of the drum 17, the relay 18 is triggered with contacts 19 and 20 (activated for the time the signal flag goes through the drum speed sensor) for the duration of the action), which by its contacts 20 closes the circuit resetting the meter to 5 fractions of meters, and also closes the contacts 21 in the circuit the counter of the meter is 6 meters.

When the start-up relay 16 is turned on, it becomes self-blocking via its own contacts 22, and also closes its contacts 23 and 24 in the counter circuit of 5 parts of a meter and a counter of 6 meters, respectively. The output of the generator 25 of them; A stable frequency pulse is connected to the counting input of a 5 meter meter counter.

The counting impulse to the input of counter 6 of the metro when the signal is first applied to the drum speed sensor (when the relay 18 is first triggered) does not pass, because by this time the contacts 26 of the time relay 11 in the circuit have not yet counted. shut up.

Upon completion of the effect of the signal flag on the drum 17 speed sensor, current flow through the winding of the counting start relay 18 stops and the latter opens its contacts 19 in the power supply circuit of relay 16 (relay 16 remains activated due to self-blocking contacts 22), opens contacts 20 in the reset counter circuit 5 parts of a meter (counter 5 starts counting fractions of a meter due to pulses from a stable frequency generator 25) and opens contacts 21 in the circuit through a counter of 6 meters.

At the second (and subsequent) effect of the signal flag on the sensor 17 of the drum speed (by this time, contacts 26 of relay 11 of time in the circuit, the counter of 6 meters is closed, and the probe drops exactly one meter), relay 18 will turn on again and its contacts 20 will produce a reset of the meter is 5 fractions of a meter, and the contacts 21 provide an impulse to the meter input of meters 6 and the meter counter remembers the unit.

At the end of the second (and subsequent) effects of the signal flag on the drum speed sensor 17 along the winding of the relay 18, the current flow stops, its contacts 20 and 21 open and the fractions of the second (and subsequent) meter begin.

This continues until the probe reaches the surface of the controlled medium (liquid) or the bottom of the process tank (reservoir).

When the probe reaches the surface of the controlled medium or the bottom of the technological capacity, the relay 27 is turned on and its open contacts 28 turn off the relay 8, the self-blocking of the relay 8 is removed (contacts 9), the time relay is turned off (contacts 10), the coil 13 of the reverser of the magnetic actuator turns off (contacts 12 ) and the drive stops, turns off the relay 16 (pins 14), opens the circuit for automatic reset of the meter fraction meter (pins 15). When the time relay 11 turns off, its contacts 26 become blurred. The circuit is connected to the meter counter 6 meter. When the relay 16 is turned off, its self-blocking is removed (by contacts 22), and its contacts 23 and 24 are disconnected in the circuit counter of the meter 5 parts of a meter and the meter 6 meters respectively.

Claims (2)

Thus, we have an intermediate state of the circuit when the spectrometer is disabled, the probe is 7 at the surface of the controlled medium or at the bottom of the process tank, the meter of 5 fractions and the meter of 6 meters store their readings, and the reset is disconnected from the control circuit; t When the time relay 27 is turned on, the NfbiKaraTCH contacts 29 are also disconnected and the locking terminal is removed from the base of the transistor 30. ; potential. After a period of time (2 seconds), defined by a chain consisting of a resistor 31 and a capacitor 32, the transistor 30 opens and turns on 33. Relay 33, with its contacts 34, switches on relay 35, which through its own contacts 36 becomes self-blocking, and contacts 37 include the coil 38 of the reversing magnetic starter, the latter includes an electric drive on the rise of the probe up. When the probe-controlled medium is broken, the relays 27 and 33 are turned off, and the relay 35 remains switched on due to self-blocking (contacts 36). Upon the return of the probe to its upper position, the limit switch 39 is triggered, the relay 35 is turned off, the magnetic starter coil 38 is turned off, the electric drive stops, and the control circuit assumes the initial state. An invention of a level measuring device comprising a probe on a cable wound on a drum with a signal flag fixed on the drum's neck and acting on a non-contact sensor of drum revolutions, a limit switch and a control circuit, different from the fact that, in order to improve the measurement accuracy, The device is equipped with a counter for the number of fractions of a drum's turn, a time relay and a pulse generator with a stable frequency, while the output of the proximity sensor for the number of revolutions of the drum is connected to the input reset the counter to lei turnover ba-. and through the make contacts of the time relay with the counting input of the drum speed counter, and the output of the stable frequency pulse generator is connected to the counting input of the drum share counter. Sources of information (taken into account during the examination 1. German Patent No. 1272013, class 42 e 34, published 1968. 2. Development and testing of equalizers for tanks in the production of aluminum and anode paste. Report 5-68-048, inv.№B049681, IF YOU, Irkutsk, 1969 (prototype). - // Ooh