GB2284053A - Detecting presence or absence of liquid in a vessel - Google Patents
Detecting presence or absence of liquid in a vessel Download PDFInfo
- Publication number
- GB2284053A GB2284053A GB9421425A GB9421425A GB2284053A GB 2284053 A GB2284053 A GB 2284053A GB 9421425 A GB9421425 A GB 9421425A GB 9421425 A GB9421425 A GB 9421425A GB 2284053 A GB2284053 A GB 2284053A
- Authority
- GB
- United Kingdom
- Prior art keywords
- electronic signal
- signal
- output
- liquid
- time interval
- 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
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring 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
- G01F23/28—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring 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 electromagnetic or acoustic waves applied directly to the liquid or fluent solid material
- G01F23/296—Acoustic waves
- G01F23/2961—Acoustic waves for discrete levels
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring 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
- G01F23/28—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring 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 electromagnetic or acoustic waves applied directly to the liquid or fluent solid material
- G01F23/296—Acoustic waves
- G01F23/2966—Acoustic waves making use of acoustical resonance or standing waves
- G01F23/2967—Acoustic waves making use of acoustical resonance or standing waves for discrete levels
Landscapes
- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Electromagnetism (AREA)
- Thermal Sciences (AREA)
- Fluid Mechanics (AREA)
- General Physics & Mathematics (AREA)
- Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
- Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
Abstract
An ultrasonic pulse is injected into the wall 12 of a pipe or vessel by a transducer 10 secured to the exterior surface of the wall 12 so as to cause ringing of the signal within the wall 12, the amplitude of which is measured by the method and compared to a threshold level so as to determine whether or not liquid is present on the other side of the wall from the transducer. The ringing signal will attenuate more rapidly in the presence of a liquid than it will in the absence of a liquid. The same transducer is used to inject the pulse and to monitor the ringing signal. The ringing signal is preferably monitored for a predetermined period following an initial blanking period. <IMAGE>
Description
Ultrasonic Liquid Sensing Method and Apparatus
The present invention relates to methods and apparatus for sensing the presence or absence of liquid within a vessel, pipe or the like using ultrasonic signals.
There are numerous applications in which it is necessary to monitor or control the levels of liquids in vessels, pipes or the like, requiring some form of detector device capable of generating a signal indicating the presence or absence of liquid at a predetermined point on the wall of the vessel. There are numerous types of level detector which may be installed inside a vessel for this purpose. However, in many cases it is preferable for the detector to be located on the outside of the vessel wall; e.g. for ease of installation and maintenance, or for hygiene reasons. Arrangements of ultrasonic transducers, which can transmit ultrasonic signals through a tank wall, have been used in the past for such non-intrusive level detection.
Hitherto known methods involving ultrasonic signals through a wall of the vessel or pipe rely on the difference in the velocity of sound through the liquid and the velocity of sound through air. A transducer mounted on the vessel wall transmits a signal into the vessel and the length of time taken for the signal to cross to a receiving transducer on the opposite vessel wall (or to be reflected from the opposite wall back to the transmitting transducer) is measured. The time taken for the signal to travel the known path length allows the presence or absence of liquid at the reference point to be determined.
Systems of this type rely on the transmitted signal reaching the opposite transducer or being reflected back to the transmitting transducer, and are therefore not suited to use with liquids containing gas bubbles or liquids which are otherwise likely to absorb or dissipate the ultrasonic signal, or with very large vessels. Also, the transducer(s) have to be accurately aligned on the tank wall(s).
In another non-intrusive, ultrasonic level detecting arrangement, first and second transducers are vertically spaced on the vessel wall, and are mounted at equal and opposite angles to the wall surface. The first sensor transmits a signal which travels through the wall by internal reflection to be detected by the second sensor. The degree of attenuation of the signal between transmission and reception provides an indication of the presence or absence of liquid on the other side of the wall. This system has been found to lack reliability and accuracy, and also requires the use of two transducers.
It is a first object of the present invention to provide methods and apparatus for detecting the presence or absence of liquid in a vessel or pipe using ultrasonic sound using a single transducer, in which the measuring signal is not required to traverse the interior of the vessel.
According to a first aspect of the invention there is provided a method of detecting the presence or absence of a liquid within a vessel or pipe, comprising the steps of:
applying an ultrasonic transducer to an outside surface of a wall of the pipe or vessel, said transducer being adapted to produce output ultrasonic signals in response to input electronic signals and to produce output electronic signals in response to input ultrasonic signals;
applying an input electronic signal pulse to said transducer so as to produce an output ultrasonic pulse into said wall;
monitoring an output electronic signal from said transducer produced in response to input ultrasonic signals arising from ringing of the originally output ultrasonic signal within said wall; and
comparing said output electronic signal with a predetermined reference and thereby determining the presence or absence of liquid on the opposite side of said wall.
Preferably, the step of monitoring said output electronic signal comprises monitoring said signal during a predetermined time interval following the application of said input electronic signal.
Preferably also, the step of comparing said output electronic signal comprises comparing the amplitude of said signal during said time interval to a predetermined threshold level.
Preferably also, the output electronic signal is blanked during a predetermined blanking interval preceding said predetermined time interval. Most preferably, the output electronic signal is also blanked following said predetermined time interval.
Preferably, said blanking interval is selected so as to minimise the amplitude of the output electronic signal detected during said predetermined time interval in the presence of liquid. Preferably also, the duration of said input electronic signal pulse is selected so as to maximise the amplitude of the output electronic signal detected during said predetermined time interval in the absence of liquid.
According to a second aspect of the invention there is provided apparatus for detecting the presence or absence of a liquid within a vessel or pipe, said apparatus comprising:
an ultrasonic transducer for attachment to an outside surface of a wall of the pipe or vessel, said transducer being adapted to produce output ultrasonic signals in response to input electronic signals and to produce output electronic signals in response to input ultrasonic signals;
electronic signal transmission means for applying an input electronic signal pulse to said transducer so as to produce an output ultrasonic pulse into said wall;
electronic signal receiver means for monitoring an output electronic signal from said transducer produced in response to input ultrasonic signals arising from ringing of the originally output ultrasonic signal within said wall; and
comparator means for comparing said output electronic signal with a predetermined reference and thereby determining the presence or absence of liquid on the opposite side of said wall.
Preferably, said electronic signal receiver means is adapted to monitor said signal during a predetermined time interval following the application of said input electronic signal.
Preferably also, said comparator means is adapted to compare the amplitude of said signal during said time interval to a predetermined threshold level.
Preferably also, the apparatus further includes signal blanking means for blanking the output electronic signal during a predetermined blanking interval preceding said predetermined time interval. Most preferably, said signal blanking means is further adapted to blank the output electronic signal following said predetermined time interval.
Preferably, said blanking means is adjustable such that the blanking interval may be selected so as to minimise the amplitude of the output electronic signal detected during said predetermined time interval in the presence of liquid.
Preferably also, said transmitter means is adjustable such that the duration of said input electronic signal pulse may be selected so as to maximise the amplitude of the output electronic signal detected during said predetermined time interval in the absence of liquid.
An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which:
Fig. 1 is a schematic block diagram of an
ultrasonic liquid sensing apparatus embodying the
invention; and
Fig. 2 is a schematic representation of various
signal wave forms applying to the method and
apparatus of the invention in the absence of
liquid (dry) and in the presence of liquid (wet).
Referring first to Fig. 1 the invention utilises an ultrasonic transducer 10 secured to a wall 12 of a vessel, pipe or the like to detect the presence or absence of a liquid on the opposite side of the wall 12. The transducer 10 may be driven by an input electronic signal so as to generate an output ultrasonic signal, and will also produce an output electronic signal in response to an applied ultrasonic signal. An electronic input pulse to the transducer 10 produces an output ultrasonic pulse in the wall 12. The ultrasonic pulse will be multiply reflected within the wall 12 producing a "ringing" effect. It has been found that the "ringing" of the ultrasonic pulse will continue for a longer period at a sustained amplitude in the absence of liquid, ie when wall 12 is dry, than in the presence of liquid, ie when wall 12 is wet.The presence of liquid appears to have the effect of dampening the "ringing".
Fig. 2b illustrates the difference between the "ringing" signals obtained with a dry wall and with a wet wall. It can be seen that the two signals are essentially similar during an initial time period, but that the dry signal continues at substantially the same amplitude for an extended period after said initial period, whereas the wet signal attenuates rapidly after the initial period. The present invention operates by discriminating between these two signal wave forms which are characteristic of a dry wall and a wet wall respectively.
Referring again to Fig.1 the sensing apparatus embodying the invention includes means for generating and transmitting an electronic pulse signal to drive the transducer and means for receiving and monitoring electronic signals subsequently generated by the transducer in response to the "ringing" of the original ultrasonic pulse. The transmitting means includes a transmitter 14 (suitably a 12 volt HT), transmitter trigger 16, an astable PRF generator 18 and first and second monostables 20, 22. The receiving means includes a radio frequency amplifier 24, a simple diode peak detector 26, and a comparator 28, suitably a variable threshold Schmitt trigger.
In order to discriminate between the dry and wet signals a blanking signal is applied to the electronic output signal from the transducer for a predetermined blanking interval T corresponding to the period during which a ringing signal is obtained in the presence of liquid, so as to blank out that portion of the "ringing" signal which occurs both in the presence and absence of liquid. The signal is then monitored during a subsequent predetermined time interval G, during which the continued ringing signal will be detected in the absence of liquid and substantially no signal will be detected in the presence of liquid. The signal is again blanked following the predetermined time interval
G so as to avoid possible interference from subsequent signals arising from further reflection of the ultrasonic pulse.
The presence or absence of liquid can thus be detected by monitoring the signal during the predetermined interval G and comparing the amplitude of the signal with a predetermined threshold value set between the values of signal amplitude obtained in the presence and in the absence of liquid respectively.
Fig. 2d shows the difference in the output from the peak detector 26 in dry and wet conditions respectively as a result of the selective blanking of the received signal. Fig. 2e shows the corresponding outputs from the comparator 28.
Comparator 28 compares the amplitude of the "ringing" signal during the interval G with a predetermined threshold level. An amplitude above the threshold level corresponds to the dry condition and a high output is obtained. Conversely, an amplitude falling below the threshold level corresponds to the wet condition and a low output is obtained.
The output signal from the comparator 28 can be used, for example, to control the operation of a relay 30, or for any other control or monitoring function as will be apparent to those of ordinary skill in the art, such as automatic feedback control of the liquid level within a vessel.
In the present embodiment, the blanking interval T, the predetermined time interval G, the signal pulse width, the amplifier gain and the comparator threshold are all adjustable for calibration purposes.
A meter 32 can be included in or connected to the apparatus for calibrating the system, as follows. With liquid present (wet) the blanking interval T is adjusted from zero to the point where the ringing signal is less than 20% full scale deflection (FSD) of the meter. With the liquid removed (dry), the meter reading obtained will be higher, and the signal pulse width is adjusted until a meter reading greater than 80% FSD is obtained. If the maximum reading obtainable by adjusting the pulse width is less than 80% FSD, then the amplifier gain may be adjusted. With liquid again present, a new reading is taken to confirm that the wet reading remains below 20%. The comparator threshold is set half way between the high (dry) and low (wet) readings.
The apparatus is thus easily calibrated using a meter and screwdriver, without the need for an oscilloscope.
The configuration of the transducer, including the choice of backing materials and coupling materials for the transducer crystal, and the selection of the signal frequency, can be varied to optimise the performance of the system with different vessel wall materials and liquids to be monitored.
Modifications and improvements may be incorporated without departing from the scope of the invention.
Claims (16)
1. A method of detecting the presence or absence of a liquid within a vessel or pipe, comprising the steps of:
applying an ultrasonic transducer to an outside surface of a wall of the pipe or vessel, said transducer being adapted to produce output ultrasonic signals in response to input electronic signals and to produce output electronic signals in response to input ultrasonic signals;
applying an input electronic signal pulse to said transducer so as to produce an output ultrasonic pulse into said wall;
monitoring an output electronic signal from said transducer produced in response to input ultrasonic signals arising from ringing of the originally output ultrasonic signal within said wall; and
comparing said output electronic signal with a predetermined reference and thereby determining the presence or absence of liquid on the opposite side of said wall.
2. A method as claimed in Claim 1, wherein the step of monitoring said output electronic signal comprises monitoring said signal during a predetermined time interval following the application of said input electronic signal.
3. A method as claimed in Claim 2, wherein the step of comparing said output electronic signal comprises comparing the amplitude of said signal during said time interval to a predetermined threshold level.
4. A method as claimed in Claim 2 or Claim 3, wherein the output electronic signal is blanked during a predetermined blanking interval preceding said predetermined time interval.
5. A method as claimed in Claim 4, wherein the output electronic signal is also blanked following said predetermined time interval.
6. A method as claimed in Claim 4 or Claim 5, wherein said blanking interval is selected so as to minimise the amplitude of the output electronic signal detected during said predetermined time interval in the presence of liquid.
7. A method as claimed in any preceding Claim, wherein the duration of said input electronic signal pulse is selected so as to maximise the amplitude of the output electronic signal detected during said predetermined time interval in the absence of liquid.
8. Apparatus for detecting the presence or absence of a liquid within a vessel or pipe, said apparatus comprising:
an ultrasonic transducer for attachment to an outside surface of a wall of the pipe or vessel, said transducer being adapted to produce output ultrasonic signals in response to input electronic signals and to produce output electronic signals in response to input ultrasonic signals;
electronic signal transmission means for applying an input electronic signal pulse to said transducer so as to produce an output ultrasonic pulse into said wall;
electronic signal receiver means for monitoring an output electronic signal from said transducer produced in response to input ultrasonic signals arising from ringing of the originally output ultrasonic signal within said wall; and
comparator means for comparing said output electronic signal with a predetermined reference and thereby determining the presence or absence of liquid on the opposite side of said wall.
9. Apparatus as claimed in Claim 8, wherein said electronic signal receiver means is adapted to monitor said signal during a predetermined time interval following the application of said input electronic signal.
10. Apparatus as claimed in Claim 9, wherein said comparator means is adapted to compare the amplitude of said signal during said time interval to a predetermined threshold level.
11. Apparatus as claimed in Claim 10, further including signal blanking means for blanking the output electronic signal during a predetermined blanking interval preceding said predetermined time interval.
12. Apparatus as claimed in Claim 11, wherein said signal blanking means is further adapted to blank the output electronic signal following said predetermined time interval.
13. Apparatus as claimed in Claim 11 or Claim 12, wherein said blanking means is adjustable such that the blanking interval may be selected so as to minimise the amplitude of the output electronic signal detected during said predetermined time interval in the presence of liquid.
14. Apparatus as claimed in any one of Claims 8 to 13, wherein, said transmitter means is adjustable such that the duration of said input electronic signal pulse may be selected so as to maximise the amplitude of the output electronic signal detected during said predetermined time interval in the absence of liquid.
15. A method of detecting the presence or absence of a liquid within a vessel or pipe, substantially as hereinbefore described with reference to the accompanying drawings.
16. Apparatus for detecting the presence or absence of a liquid within a vessel or pipe, substantially as hereinbefore described with reference to the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB939321942A GB9321942D0 (en) | 1993-10-25 | 1993-10-25 | Ultrasonic liquid sensing method and apparatus |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9421425D0 GB9421425D0 (en) | 1994-12-07 |
| GB2284053A true GB2284053A (en) | 1995-05-24 |
| GB2284053B GB2284053B (en) | 1997-06-18 |
Family
ID=10744062
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB939321942A Pending GB9321942D0 (en) | 1993-10-25 | 1993-10-25 | Ultrasonic liquid sensing method and apparatus |
| GB9421425A Expired - Fee Related GB2284053B (en) | 1993-10-25 | 1994-10-25 | Ultrasonic liquid sensing method and apparatus |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB939321942A Pending GB9321942D0 (en) | 1993-10-25 | 1993-10-25 | Ultrasonic liquid sensing method and apparatus |
Country Status (1)
| Country | Link |
|---|---|
| GB (2) | GB9321942D0 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0769685A2 (en) * | 1995-10-17 | 1997-04-23 | Endress + Hauser GmbH + Co. | System for monitoring a predetermined level of a fluid in a container |
| GB2321107A (en) * | 1997-01-14 | 1998-07-15 | Smiths Industries Plc | Fluid level detector |
| US9957794B2 (en) | 2014-05-21 | 2018-05-01 | Weatherford Technology Holdings, Llc | Dart detector for wellbore tubular cementation |
| US11154796B2 (en) | 2018-11-16 | 2021-10-26 | Infinite Automated Solutions Llc | Apparatus, systems, and methods for automated separation of sand from a wellbore slurry |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102014113470A1 (en) * | 2014-09-18 | 2016-03-24 | Maschinenfabrik Reinhausen Gmbh | Electric device with a housing filled with insulating oil and measuring device and method for monitoring such an electrical device |
| EP3822660A1 (en) | 2019-11-13 | 2021-05-19 | ABB Schweiz AG | Integrity detection system for an ultrasound transducer |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB826789A (en) * | 1957-04-17 | 1960-01-20 | Bailey Meters Controls Ltd | Improvements in apparatus for indicating the level of a body of liquid |
| US4144517A (en) * | 1977-08-05 | 1979-03-13 | Joseph Baumoel | Single transducer liquid level detector |
| US4203324A (en) * | 1977-08-05 | 1980-05-20 | Joseph Baumoel | Sonic liquid level detector |
| GB2050604A (en) * | 1979-05-14 | 1981-01-07 | Chemetron Corp | Liquid level detector |
-
1993
- 1993-10-25 GB GB939321942A patent/GB9321942D0/en active Pending
-
1994
- 1994-10-25 GB GB9421425A patent/GB2284053B/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB826789A (en) * | 1957-04-17 | 1960-01-20 | Bailey Meters Controls Ltd | Improvements in apparatus for indicating the level of a body of liquid |
| US4144517A (en) * | 1977-08-05 | 1979-03-13 | Joseph Baumoel | Single transducer liquid level detector |
| US4203324A (en) * | 1977-08-05 | 1980-05-20 | Joseph Baumoel | Sonic liquid level detector |
| GB2050604A (en) * | 1979-05-14 | 1981-01-07 | Chemetron Corp | Liquid level detector |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0769685A2 (en) * | 1995-10-17 | 1997-04-23 | Endress + Hauser GmbH + Co. | System for monitoring a predetermined level of a fluid in a container |
| EP0769685A3 (en) * | 1995-10-17 | 1998-01-07 | Endress + Hauser GmbH + Co. | System for monitoring a predetermined level of a fluid in a container |
| GB2321107A (en) * | 1997-01-14 | 1998-07-15 | Smiths Industries Plc | Fluid level detector |
| US9957794B2 (en) | 2014-05-21 | 2018-05-01 | Weatherford Technology Holdings, Llc | Dart detector for wellbore tubular cementation |
| US11154796B2 (en) | 2018-11-16 | 2021-10-26 | Infinite Automated Solutions Llc | Apparatus, systems, and methods for automated separation of sand from a wellbore slurry |
| US11772015B2 (en) | 2018-11-16 | 2023-10-03 | Infinite Automated Solutions Llc | Apparatus, systems, and methods for automated separation of sand from a wellbore slurry |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2284053B (en) | 1997-06-18 |
| GB9321942D0 (en) | 1993-12-15 |
| GB9421425D0 (en) | 1994-12-07 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20111025 |