GB2034470A - Level detector for free-flowing and viscous materials - Google Patents

Level detector for free-flowing and viscous materials Download PDF

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Publication number
GB2034470A
GB2034470A GB7844314A GB7844314A GB2034470A GB 2034470 A GB2034470 A GB 2034470A GB 7844314 A GB7844314 A GB 7844314A GB 7844314 A GB7844314 A GB 7844314A GB 2034470 A GB2034470 A GB 2034470A
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GB
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Patent type
Prior art keywords
oscillation
system
mechanical
output
level
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB7844314A
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GB2034470B (en )
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BARANOVSKY A
MARKELOV V
Original Assignee
Baranovsky A
Markelov V
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date

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Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01FMEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00Indicating or measuring liquid level, or level of fluent solid material, e.g. indicating in terms of volume, indicating by means of an alarm
    • G01F23/22Indicating or measuring liquid level, or level of fluent solid material, e.g. indicating in terms of volume, indicating by means of an alarm by measurement of physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
    • G01F23/28Indicating or measuring liquid level, or level of fluent solid material, e.g. indicating in terms of volume, indicating by means of an alarm by measurement of physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring the variations of parameters of electric or acoustic waves applied directly to the liquid or fluent solid material
    • G01F23/296Acoustic waves
    • G01F23/2966Acoustic waves making use of acoustical resonance or standing waves
    • G01F23/2967Acoustic waves making use of acoustical resonance or standing waves for discrete levels

Abstract

In a level detector a mechanical oscillation system (1) is periodically excited by short pulses from an impact oscillator (2). Free oscillations are amplified in an amplifier (3) and an indication is produced by an indicating device (4) if the amplitude exceeds a certain threshold.The amplified signals are clipped in a voltage limiter (5) and differentiated in a network (6) to produce pulses which synchronise the impact oscillator (2) with the natural oscillations of the mechanical oscillation <IMAGE>

Description

SPECIFICATION Level detector for free-flowing and viscous materials This invention relates to a level detector for freeflowing and viscous materials.

A vibration-type level detector forfree-flowing and viscous materials, comprising a level-detecting probe made in the form of a mechanical oscillation system and a device for exciting this mechanical oscillation system and converting oscillations thereof into electric oscillations, electrically connected through an amplifier to an output indicating device, further includes according to the invention an impact oscillator adapted for impact excitation of the mechanical oscillation system, having an output connected to the level-detecting probe and to the input of the amplifier, a voltage amplitude limiter having an input connected to the output of the amplifier, and a differentiating network having its input connected to the output of the voltage amplitude limiter and its output electrically connected to the impact oscillator of the mechanical oscillation system.

Such construction of the vibration-type level detector enables periodical forced excitation of the mechanical oscillation system in synchronism with the natural oscillations of the oscillation system.

Therefore variation of the natural oscillation fre quencyofthe mechanical oscillation system, which occur under operating conditions due to sticking of the material onto the level-detecting probe, ambient temperature, aging of the material from which the probe is constructed, and the like, does not effect the operation of the level detector.

Given below is an embodiment of the invention taken in conjunction with the accompanying drawins.

A vibration-type level indicator for free-flowing and viscous materials comprises a level-detecting probe 1 (Figure 1) connected to an output of an impact oscillator 2 and to an input of an amplifier 3.

Connected to an output of the amplifier 3 are an output indicating device 4 and a voltage amplitude limiter 5, the output of which is connected through a differentiating network 6 to the impact oscillator 2.

The level-detecting probe 1 includes a mechanical oscillation system 7 made in the form of a rod fixed on a membrane 9 mounted on a base 10. The level-detecting probe 1 further includes a device 11 for exciting the mechanical oscillation system 7 and converting oscillations thereof into electric oscillations, comprising windings 12 with a ferromagnetic core 13 serving as an electromagnet and magnetic displacement transducer for converting oscillation of the mechanical oscillation system into voltage variation having a frequency equal to the oscillation frequency ofthe mechanical oscillation system.

In the preferred embodiment of the invention the impact oscillator 2 comprises a thyristor 14 (Figure 3) connected with the winding 12 through a discharge capacitor 15. Charging the capacitor 15 is effected a resistor 16 from a power source whose output 17 is shown in Figure 3. Timing circuit of the impact oscillator 2 is made in the form of an emitter foilower comprising a transistor 18. A basic circuit of the transistor 18 includes a timing RC circuit formed by a resistor 19 and a charging capacitor 20. An emitter circuit of the emitter follower includes a stabilotron 21 for setting an operation threshold of the thyristor 14. The current of the transistor 18 at the moment of its being rendered conducting is limited by a resistor 22, whereas a resistor 23 together with an input impendance of the thyristor 14 from a load of said emitter follower.A diode 24 serves for discharging the charging capacitor 20 at the moments when the thyristor 14 comes into action.

Figure 3 represents the differentiating network 6 comprising a resistor 25, a capacitor 26 and a diode 27.

The amplifier 3 comprises two transistors 28, 29 (Figure 4) with direct connections between stages.

Direct current regime of the amplifier is provided by a RC circuit comprising resistors 30, 31 and a capacitor 32. Resistors 33, 34 form a load in the amplification stages. Capacitors 35, 36 provide separation of the direct current connections. A resistor 37 provides connection with sinchronization circuits. A stabilotron 38 is the high-pass limiter 5 of the output voltage amplitude of the amplifier 3. A capacitor 39 precludes excitation of the amplifier 3 at high frequencies.

The output indicating device 4, shown in Figure 5, comprises a transistor 40 in the collector circuit of which there is included an electomagnetic relay 41 which is shunted by a capacitor 42. An emitter circuit of the transistor 40 includes a stabilotron 43 for setting operation threshold of the output indicating device 4. A basic circuit of the transistor 40 comprises diodes 44 and 45 serving as a detector, and a capacitor 46 with a resistor 47. A circuit comprising a resistor 48 and stabilotron 49 generates an output signal for contactless automatic devices. The relay 41 has contacts 50,51 for switching on and off respective indicator tubes 52 and 53.

The proposed level indicatorforfree-flowing and viscous materials operates as follows.

The impact oscillator 2 produces short pulses the duration of which is considerably shorter than the period of natural oscillations of the mechanical oscillation system 7 with the repetition period being several times longer than the period of natural oscillations of the mechanical oscillation system.

Short pulses produced by the oscillator 2 are applied to the winding 12 and thereby exciting by impacts the mechanial oscillation system 7. In a released state the mechanical oscillation system 7 possesses a high quality factor, owing to which its oscillations does not attenuate during the period between successive pulses.

In the intervals between two successive exciting pulses the oscillations of the mechanical oscillation system is received by the same winding 12 and converted to an alternating voltage which is applied to the input of the amplifier 3 connected with the winding 12. After being amplified by the amplifier 3 said voltage the frequency of which coincides with the natural oscillation frequency of the mechanical oscillation system 7, is applied to the input of the output indicating device 4.

The alternating voltage is converted in the output indicating device 4 into the direct voltage which cause the actuating electromagnetic relay to operate. With its contacts 50 and 51 the relay 41 closes the feeding circuit of the tube 52 or 53 indicative of the presence or absence of the material at the location of the mechanical oscillaltion system 7.

Being amplified by the amplifier 3 the alternating voltage is passed into the voltage amplitude limiter 5 wherein it undergoes peak limiting so that at the output of the amplitude limiter there is formed an alternating voltage which is close by its form to the square one. The resultant pulses are differentiated by the differentiating network 6 connected to the output of the limiter 5. As a result at the output of the differentiating network 6 there is formed a train of synchronizing pulses each coinciding in time with the start of the oscillation periods of the mechanical oscillation system 7.

In the intervals between successive exciting pulses the oscillations of the mechanical oscillation system are received by the same winding 12 and converted into an alternating voltage which is applied to the input of the amplifier 3 connected with the winding 12. After being amplified by the amplifier 3 said voltage the frequency of which coincides with the natural oscillation frequency of the mechanical oscillation system 7, is applied to the input of the output "nicating device 4.

The synchronizing pulses initiate the impact oscillator 2 at moments corresponding to the start of the oscillation periods of the mechanical oscillation system 7. As the exciting pulses pass from the output of the impact oscillator 2 to the winding 12 interacting with the mechanical oscillation system 7, periodical impact pulses produced by said winding will coincide in-phase with oscillations of the mechanical oscillation system 7 thereby maintaining the oscillation as its natural frequency.

In case when the level-detecting probe 1 is covered by the material the quality factor of the mechanical oscillation system considerably lowers and its oscillations after being excited by the exciting pulse of the impact oscillator 2, rapidly attenuate. As a result to the output of the output indicating device 4 are passed only very short exciting pulses which after being averaged in the circuit comprising elements 40, 41,42, 44,45,46,47 (Figure 5) produce in the basic circuit of the transistor 40 a direct voltage which is much lower than the operation threshold thereof set by the stabilotron 43, the current of the 40 decreasing and thereby deenergizing the electromagnetic relay 41. The contacts 50, 51 of the relay 41 switch on a respective tube indicating the presence of material at the location of the level-detecting probe.Changes in the natural oscillation frequency of the mechanical oscillation system 7 which may occur under operating conditions due to the change of its mass as a result of sticking of the material onto the probe or because of the change of the rigidity caused by the ambient temperature variation, or aging of the material from which the oscillation system is constructed, does not affect the operation of the oscillation system, since with the change of the frequency of the oscillation system the timing of the synchronizing pulses also changes.

Thus in the proposed device owing to the periodical forced excitation of the mechanical oscillation system 7, effected by the impact exciter 2 and synchronized with the alternating voltage produced by converting said oscillations, there is achieved precise matching of the excitation with the natural oscillation frequency of the mechanical oscillation system, thereby improving the reliability of the level detector and simplifying the construction of the level-detecting probe.

Claims (2)

1. A vibration-type level detector for free-flowing and viscous materials, comprising a level-detecting probe made in the form of a mechanical oscillation system, and a device for exciting oscillations in the mechanical oscillation system and converting said oscillations into electrical oscillations, said device being electrically connected through an amplifier to an output indicating device; an impact oscillator adapted for impact excitation of the mechanical oscillation system and having an output connected to the level-detecting probe and to an input of the amplifier; a voltage amplitude limiter having an input connected to an output of the amplifier; a differentiating network connected with its input to an output of the voltage amplitude limiter and electrically connected with its output to the impact oscillator adapted for impact excitation of the mechanical oscillation system.
2. A vibration-type level detector for free-flowing and viscous materials substantially as hereinbefore described with reference to, and as shown in the accompanying drawings.
GB7844314A 1978-11-13 1978-11-13 Level detector for freeflowing and viscous materials Expired GB2034470B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB7844314A GB2034470B (en) 1978-11-13 1978-11-13 Level detector for freeflowing and viscous materials

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB7844314A GB2034470B (en) 1978-11-13 1978-11-13 Level detector for freeflowing and viscous materials

Publications (2)

Publication Number Publication Date
GB2034470A true true GB2034470A (en) 1980-06-04
GB2034470B GB2034470B (en) 1983-01-19

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB7844314A Expired GB2034470B (en) 1978-11-13 1978-11-13 Level detector for freeflowing and viscous materials

Country Status (1)

Country Link
GB (1) GB2034470B (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3721213A1 (en) * 1987-06-26 1989-01-05 Vega Grieshaber Gmbh & Co Level measuring device
US5035140A (en) * 1988-11-03 1991-07-30 The Boeing Company Self cleaning liquid level detector

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3721213A1 (en) * 1987-06-26 1989-01-05 Vega Grieshaber Gmbh & Co Level measuring device
DE3721213C2 (en) * 1987-06-26 1998-04-09 Grieshaber Vega Kg level meter
US5035140A (en) * 1988-11-03 1991-07-30 The Boeing Company Self cleaning liquid level detector

Also Published As

Publication number Publication date Type
GB2034470B (en) 1983-01-19 grant

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PCNP Patent ceased through non-payment of renewal fee