CA1111941A - Turbine rotational speed measurement and control utilizing a x-band doppler transceiver - Google Patents
Turbine rotational speed measurement and control utilizing a x-band doppler transceiverInfo
- Publication number
- CA1111941A CA1111941A CA293,494A CA293494A CA1111941A CA 1111941 A CA1111941 A CA 1111941A CA 293494 A CA293494 A CA 293494A CA 1111941 A CA1111941 A CA 1111941A
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- CA
- Canada
- Prior art keywords
- output
- pulse
- signal
- frequency
- rotating object
- 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.)
- Expired
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/50—Systems of measurement based on relative movement of target
- G01S13/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
- G01S13/583—Velocity or trajectory determination systems; Sense-of-movement determination systems using transmission of continuous unmodulated waves, amplitude-, frequency-, or phase-modulated waves and based upon the Doppler effect resulting from movement of targets
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- Engineering & Computer Science (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Computer Networks & Wireless Communication (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Radar Systems Or Details Thereof (AREA)
- Control Of Velocity Or Acceleration (AREA)
- Magnetic Bearings And Hydrostatic Bearings (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An electromagnetic system using a Doppler transceiver for the control and monitoring of the rotation speeds of various objects such as turbines. A digital readout of the revolutions per minute of the object is produced and thumb wheel counters are utilized to provide a maximum speed reference, which if exceeded, initiates a pulse to activate a solid gate relay for governor control.
The system described is effective over RPM ranges of 250 to 30,000 RPM and the accuracy of speed measurement within plus or minus one-half percent. The range can be readily increased by using additional circuitry.
An electromagnetic system using a Doppler transceiver for the control and monitoring of the rotation speeds of various objects such as turbines. A digital readout of the revolutions per minute of the object is produced and thumb wheel counters are utilized to provide a maximum speed reference, which if exceeded, initiates a pulse to activate a solid gate relay for governor control.
The system described is effective over RPM ranges of 250 to 30,000 RPM and the accuracy of speed measurement within plus or minus one-half percent. The range can be readily increased by using additional circuitry.
Description
This invention is directed to a Doppler radar technique for monitoring the revolutions per minute of rotating objects. More particularly, this invention is directed to a contactless system for the monitoring of the revolutions per minute of the shaft of a gas turbine using a Doppler radar technique.
BACKGROUND OF THE INVENTION
Presently used methods of monitoring the revolutions per minute of rotating objects such as gas turbines rely upon the use of devices or systems which are physically coupled to the turbine through moving parts. Because physical wear is involved, the devices and systems wear out in time, require maintenance to correct errors, and frequently need replacement. Some systems are coupled to the rotating object through moving parts, other systems involve the use of rotary transformers, and still other systems utilize magnetic pickups. Although all of these techniques are effective in their own right~ and for the purposes required, they all have shortcomings.
The use of rotary transformers is frequently satisfactory, but the cost of additional equipment makes these techniques expensive. Magnetic pickup systems are also useful but suffer from installation problems and high cost. Stroboscopes are often used to synchronize a flashing light with the shaft rotation, making the shaft appear stationary. While this instrument offers a non-contacting method of rotational velocity measurement, thereby eliminatin~ wear of moving parts, it has the disadvantage of being able to synchronize on harmonics of the fundamental shaft speed, thus requiring the user ~i~
--2-- ~7 . .
-- . ..
, to know the approxim2te velocity at which the object, e.g. shaft, is rotating in order to avoid error. While the stroboscope lends itself to discrete monitoring, it is impractical for continuous monitoring or speed control.
SUMMARY OF THE INVENTION
The inventors have developed a non-contact method for measuring and monitoring the speed of rotation of a rotating object such as the shaft of a gas turbine which has reliability and accuracy, requires an insignificant alteration to existing installations and is economical to install. The contactless method of monitoring the rotation of the rotating object such as a gas turbine shaft is done utili~ing a Doppler radar technique which involves no moving parts and has solid-state reliability.
The principle of operation is based on the shift in frequency resulting from the reflection of a radio signal from a moving body. The frequency difference provides a direct correlateable indication of the speed of the moving body, for example, a rotating turbine shaft.
When a rotating object such as a turbine shaft is beamed at an angle to the axis by a Doppler type radar, the presence of any mechanical imbalance in the shape of the rotating object (e.g. shaft) for example balancing holes, screws, keyways, slots or protrusions, surface roughness, etc. gives rise to bursts of Doppler signals which can be readily identified and evaluated by signal processing.
Any beam angle will work and the strength of the returned signal is roughly proportional to the cosine of the angle.
According to experimented evidence, a beam angle of 90 may not necessarily be optimum - the optimum angle is dependent on shaft discontinuity geometry. Each revolution of the object produces an identical pattern and these may be monitored using a counter to read the revolutions per minute of the object (e.g. turbine shaft). The degree of electrical imbalance required to give a useful signal is very small and one can usually rely on normal surface roughness of the object to give adequate reflection for satisfactory operation of the technique, unless discontinuities exist which give larger bursts of a return signal.
The invention is directed to a method of measuring, controlling and monitoring the rotational speed of a rotating member comprising employing a Doppler effect transceiver to measure the rotation speed of the rotating member, feeding the signal from the Doppler transceiver into an amplifier, subsequently into a wave shaper, subse~uently into a digital multiplier, subsequently into a readout and comparator, and finally into control circuitry which, if the rotational speed of the object ; ~20 exceeds a predetermined speed, shuts down the member.
The invention also includes a method of measuring, monitoring and controlling the rotational shaft speed of a turbine by utilizing a Doppler transceiver which detects discontinuities on the surface of the rotating shaft of the turbine, whereby the audio output of the Doppler transceiver is amplified and is then fed into a wave shaper which eliminates the harmonics, renders the signal compatikle with logic being used in the system, the signal being multiplied by a digital frequency multiplier and being fed into a readout, the - .
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fre~uency of the signal being fed into the readout whereby it is monitored by a comparator, and if the frequency exceeds a predetermined set point, the comparator produces a pulse which is utilized to activate speed control circuitry attached to the rotating shaft of the turbine. A 3 milli watt transceiver can be used.
The output of the transceiver can be directed onto the rotating shaft by a horn, or an antenna system, and can be shielded to prevent the movement of objects other than the rotating shaft being monitored from affecting the transceivers electromagnetic field.
The invention is also directed to a method of determining the rate of rotation of a rotating object comprising utilizing an electronic measuring means based on the Doppler effect for transmitting a signal for reflection off a rotating object and receiving the signal reflected from the rotating object and mixing the signal to produce an audio signal with a frequency proport-ional to the rotational speed of the rotating body.
In the invention described above, the output signal from the Doppler measuring unit can be amplified to 5 Volt (5 V) peak whereby it is easily shaped for TTL compatibility using a one shot and is reduced to a fundamental harmonic by a fre~uency divider circuit. The method can employ amplifier/wav~ shaper means to produce one pulse per revolution and such pulses are counted for one second utilizing an X 60 multiplier means.
Multiplication can be accomplished by dividing the period of the incoming frequency by the multiplicand, a 10 MHz pulse train being gated by the incoming frequency into a counting circuit, the aacumulated pulse count, for one period being then divided by the multiplicand and being fed into a down counting circuit clocked at 10 MHz, the resulting output frequency therefore being greater according to the multiplicand ratio than the incoming frequency.
A digital readout means can be used whereby the multiplier is divided into three decades to reduce resolution error. The readout value can be compared with a thumb wheel switch means value preset by means of digital circuitry, and if the readout value exceeds the set on the thumb wheel switch, a latch relay means can be pulsed which in turn closes a set of contacts to shut down the rotating object.
The invention is also an electromagnetic system operable for measuring, and monitoring the rotational speed of a rotating object comprising in combination the following elements:
(1) A continuous wave Doppler transceiver which is operable to transmit an electromagnetic signal towards the rotating object. The Doppler transceiver is operable to receive an electromagnetic signal reflected from the rotating object and produces an audio fre~uency output electrical signal. The period of the audio frequency output electrical signal is inversely proportional to the rotational speed of the rotating object.
BACKGROUND OF THE INVENTION
Presently used methods of monitoring the revolutions per minute of rotating objects such as gas turbines rely upon the use of devices or systems which are physically coupled to the turbine through moving parts. Because physical wear is involved, the devices and systems wear out in time, require maintenance to correct errors, and frequently need replacement. Some systems are coupled to the rotating object through moving parts, other systems involve the use of rotary transformers, and still other systems utilize magnetic pickups. Although all of these techniques are effective in their own right~ and for the purposes required, they all have shortcomings.
The use of rotary transformers is frequently satisfactory, but the cost of additional equipment makes these techniques expensive. Magnetic pickup systems are also useful but suffer from installation problems and high cost. Stroboscopes are often used to synchronize a flashing light with the shaft rotation, making the shaft appear stationary. While this instrument offers a non-contacting method of rotational velocity measurement, thereby eliminatin~ wear of moving parts, it has the disadvantage of being able to synchronize on harmonics of the fundamental shaft speed, thus requiring the user ~i~
--2-- ~7 . .
-- . ..
, to know the approxim2te velocity at which the object, e.g. shaft, is rotating in order to avoid error. While the stroboscope lends itself to discrete monitoring, it is impractical for continuous monitoring or speed control.
SUMMARY OF THE INVENTION
The inventors have developed a non-contact method for measuring and monitoring the speed of rotation of a rotating object such as the shaft of a gas turbine which has reliability and accuracy, requires an insignificant alteration to existing installations and is economical to install. The contactless method of monitoring the rotation of the rotating object such as a gas turbine shaft is done utili~ing a Doppler radar technique which involves no moving parts and has solid-state reliability.
The principle of operation is based on the shift in frequency resulting from the reflection of a radio signal from a moving body. The frequency difference provides a direct correlateable indication of the speed of the moving body, for example, a rotating turbine shaft.
When a rotating object such as a turbine shaft is beamed at an angle to the axis by a Doppler type radar, the presence of any mechanical imbalance in the shape of the rotating object (e.g. shaft) for example balancing holes, screws, keyways, slots or protrusions, surface roughness, etc. gives rise to bursts of Doppler signals which can be readily identified and evaluated by signal processing.
Any beam angle will work and the strength of the returned signal is roughly proportional to the cosine of the angle.
According to experimented evidence, a beam angle of 90 may not necessarily be optimum - the optimum angle is dependent on shaft discontinuity geometry. Each revolution of the object produces an identical pattern and these may be monitored using a counter to read the revolutions per minute of the object (e.g. turbine shaft). The degree of electrical imbalance required to give a useful signal is very small and one can usually rely on normal surface roughness of the object to give adequate reflection for satisfactory operation of the technique, unless discontinuities exist which give larger bursts of a return signal.
The invention is directed to a method of measuring, controlling and monitoring the rotational speed of a rotating member comprising employing a Doppler effect transceiver to measure the rotation speed of the rotating member, feeding the signal from the Doppler transceiver into an amplifier, subsequently into a wave shaper, subse~uently into a digital multiplier, subsequently into a readout and comparator, and finally into control circuitry which, if the rotational speed of the object ; ~20 exceeds a predetermined speed, shuts down the member.
The invention also includes a method of measuring, monitoring and controlling the rotational shaft speed of a turbine by utilizing a Doppler transceiver which detects discontinuities on the surface of the rotating shaft of the turbine, whereby the audio output of the Doppler transceiver is amplified and is then fed into a wave shaper which eliminates the harmonics, renders the signal compatikle with logic being used in the system, the signal being multiplied by a digital frequency multiplier and being fed into a readout, the - .
- -~ $ ~ ~ L ~
fre~uency of the signal being fed into the readout whereby it is monitored by a comparator, and if the frequency exceeds a predetermined set point, the comparator produces a pulse which is utilized to activate speed control circuitry attached to the rotating shaft of the turbine. A 3 milli watt transceiver can be used.
The output of the transceiver can be directed onto the rotating shaft by a horn, or an antenna system, and can be shielded to prevent the movement of objects other than the rotating shaft being monitored from affecting the transceivers electromagnetic field.
The invention is also directed to a method of determining the rate of rotation of a rotating object comprising utilizing an electronic measuring means based on the Doppler effect for transmitting a signal for reflection off a rotating object and receiving the signal reflected from the rotating object and mixing the signal to produce an audio signal with a frequency proport-ional to the rotational speed of the rotating body.
In the invention described above, the output signal from the Doppler measuring unit can be amplified to 5 Volt (5 V) peak whereby it is easily shaped for TTL compatibility using a one shot and is reduced to a fundamental harmonic by a fre~uency divider circuit. The method can employ amplifier/wav~ shaper means to produce one pulse per revolution and such pulses are counted for one second utilizing an X 60 multiplier means.
Multiplication can be accomplished by dividing the period of the incoming frequency by the multiplicand, a 10 MHz pulse train being gated by the incoming frequency into a counting circuit, the aacumulated pulse count, for one period being then divided by the multiplicand and being fed into a down counting circuit clocked at 10 MHz, the resulting output frequency therefore being greater according to the multiplicand ratio than the incoming frequency.
A digital readout means can be used whereby the multiplier is divided into three decades to reduce resolution error. The readout value can be compared with a thumb wheel switch means value preset by means of digital circuitry, and if the readout value exceeds the set on the thumb wheel switch, a latch relay means can be pulsed which in turn closes a set of contacts to shut down the rotating object.
The invention is also an electromagnetic system operable for measuring, and monitoring the rotational speed of a rotating object comprising in combination the following elements:
(1) A continuous wave Doppler transceiver which is operable to transmit an electromagnetic signal towards the rotating object. The Doppler transceiver is operable to receive an electromagnetic signal reflected from the rotating object and produces an audio fre~uency output electrical signal. The period of the audio frequency output electrical signal is inversely proportional to the rotational speed of the rotating object.
(2) Amplifier ~ and wave shaper means which receive the audio frequency output electrical signal from the Doppler transceiver for generating a train of electrical pulses.
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(3) Multiplication means for increasing the pulse repetition rate of the pulse train.
(4) Pulse counting means for counting the total number of pulses output from the multiplication means in a desired time period
(5) Comparison means for comparing the total number of pulses counted in a given period of time with a pre-selected value.
The electromagnetic system described above may further 10 include control means connected to the output of the comparison means. The control means are operable for controlling the rotational speed of the rotating object.
The rotational speed of the object is increased if the number of pulses counted by the pulse counting means in the desired time period is less than the pre-selected value. However, if the number of pulses counted by the pulse counting means in the desired time period is greater than the pre-selected value then the control means reduce the rotational speed of the object.
According to another aspect of the invention, there ; is provided hn electromagnetic apparatus operable for measuring and controlling the rotational speed of a rotating ; object, comprising in combination the following:
(a) A continuous wave Doppler transceiver comprising a radar frequency electromagnetic transmitter and a radar fre~uency electromagnetic Feceiver. The transmitter is operable to transmit a radar frequency electromagnetic signal towards the rota~ing object via an antenna system. The receiver is operable to to receive at least a portion of the signal reflected ~i - 6a -from the rotating object. The reflected signal is mixed with a portion o~ the transmitted signal in the receiver so as to generate an output audio frequency electrical signal whose period is inversely proportional to the rotational speed of the rotating object.
(b) A low noise electronic amplifier coupled to the output of the transceiver for amplifying the magnitude of the output audio signal of the transceiver.
(c) Wave shaper means connected to the output of the amplifier for generating a train of electrical pulses.
An integer number of pulses corresponds to each revolution of the rotating object.
(d) Frequency multiplier means are connected to the output of the wave shaper means for multiplying the pulse repetition rate of the pulse train which appears at the output of the wave shaper means. The pulse repetition rate of the pulse train is multiplied by a second integer and thereby reduces the time required to make a measurement of the rotational speed of the -~
rotating object. The output pulse train from the ~ frequency multiplier means has a pulse repetition rate ; exceeding the pulse repetition rate of the input pulse train by a fa~tor equal to the second integer.
(e) Digital readout means, connected to the output of the frequency multiplier means for counting the number of pulses at the output of the frequency multiplier means in a desired period of time and thereby providing an indication of the number of revolutions of the rotating object in the desired period of time.
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(f) Comparison mear.s coupled to the readout means operable for comparing the number of revolutions of the rotating object in the desired period of time with a predetermined number.
(g) Control means connected to the comparison means for controlling the rotational speed of the rotating object.
In the system described above, the frequency multiplier means may comprise:
(a) First means for generating a first pulse train of known pulse repetition rate and period.
(b) Second means, coupled to the first pulse train generating means, for generating a second pulse train having a pulse repetition rate equal to the known pulse repetition rate of the first pulse train multiplied by the reciprocal of the second integer.
(c) Means for gating the second pulse train by the input pulse train to the frequency multiplier means.
(d) Counting means, coupled to the output of the gating means, for counting the number of pulses output from the gating means during a selected period of time corresponding to the period of the input pulse train.
(e) A down counting aircuit, coupled to the output of the counting means, the down counting circuit being clocked at the ~irst pulse train repetition rate, the output pulse train o~ the down counting circuit, being the output pulse train of the frequency multiplier means, having a pulse rate exceeding that of the input pulse train by a multiplicand equal to the second integer.
. -, :.,.. . ~ ', .- - ' . :
_ WINGS
In the drawings:
FIGURE 1 represents a block diagram of a digital readout tachometer.
DETAILED DESCRIPTION OF THE INVENTION_ A transceiver, while mainly used in the past for the measurement of linear velocities, is utilized for the measurement of rotational velocities. The module transmits a microwave signal, and mi~es the signal reflected from a linearly moving or rotationally moving object to produce an audio signal whose period is inversely proportional to either the linear or the rotational speed of the object being observed. This signal is then processed by analog and digital circuitry to give the desired readout.
For angular velocity measurement, the transceiver is used to detect discontinuities on the surface of the rotating member, e.g., shaft surface. Even minute discon-tinuities on a rotating member have been shown to produce audio signals. Using a 3 mW transceiver, signals of the order of tens of mV- peak have been measured from a machined shaft and in the order of tens ofJuV-peak from a rotating he~a~onal nut.
The main advantage of using a Doppler transceiver system is that it is non-contacting. The rotating member e.g. turbine shaft, does not have to drive any mechanisms, and no modifications have to be made to the member, that is, the attachment of magnets or reflective tape. The output of the transceiver merely has to be directed onto the member via a horn, or other antenna system, and shielded to prevent the movement of objects other than the member :
' .. .. , : ' ` ~ ~ ' ' being monitored from affecting the transceivers electromagnetic field and introducing extraneous signals. The economics of using a Doppler transceiver also make it attractive over other RPM measuring devices available on the market.
Since the receiver detects discontinuities on the rotating surface, the only real disadvantage of this system is that the readout may be a multiple of the actual velocity of the rotating member. This problem is easily overcome by using analog circuitry to eliminate the lower level discontinuity si~nals and then using digital circuitry to eliminate whatever harmonics are left. However, the unit must be individually calibrated for each shaft to be monitored.
As shown in Figure 1 (which shows a block diagram of the digital readout tachometer) the audio output of the Doppler transceiver is amplified and is then fed into the wave shaper which eliminates the harmonics as described previously, and makes the signal compatible with the logic being used. The signal is then multiplied by a digital frequency multiplier and is fed into a readout. The fre~uency of the signal being fed into the readout is monitored by a comparator. If this frequency exceeds a predetermined set point, the comparator produces a pulse which is used to activate the turbines speed control circuitry.
TTL was used to construct the logic, however other types of logics such as CMOS could also have been used. It is also conceivable that a CPU could have been used in place of the logic.
The Doppler transceiver that has been used is a preconstructed microwave device that is now commonly .
., .... ,. . , , . ~
available on the electronics market-place. The Doppler transceiver transmits a signal in the 10 GHz region, receives the reflected signal and mixes the signals to produce an audio signal whose frequency is proportional to the linear or rotational speed of the moving or rotating body at which its transmitted beam is directed, and is also proportional to the number of discontinuities on the surface of the rotating body. Even minute surface discontinuities produce measurable audio signals.
A low noise amplifying circuit is required since the output signal of the Doppler transceiver unit in some cases may be quite small (10uV peak). Once the signal is amplified to SV peak, it is readily shaped for TTL
compatibility using a one shot and is reduced to its fundamental harmonic by a frequency divider circuit.
Any frequency Doppler module may be used.
The system also uses an amplifier/wave shaper which produces one pulse per revolution of the rotating member e.g. turbine shaft. To obtain a readout in revolutions per minute, it would normally be necessary to count pulses for one minute. This is a rather long and impractical counting time and was considered by the inventors to be potentially detrimental. This was so because any circuit used to detect excessive speed of the member e.g. turbine shaft (overspeed detector) would be connected to the counting circuit and there was therefore the possibility of the turbine, for example, running a full minute at an excessive and possibly dangerous speed before the shut down sequence would be initiated. A more reasonable solution would be to count for only one second, thus requiring an x60 multiplier.
~ . :
A computerized study showed that it would be best to divide the meter range into three decades, 30 to 300, 300 to 3,000 and 3,000 to 30,000 RPM. The multiplier was assigned a different multiplicand for each decade: 600 for 30 to 300, 60 for 300 to 3,000 and 6 for 3,000 to 30,000. The result of this decadization was to assure a maximum quantitization error of 0.1 percent in the multiplier. This technique also reduced the resolution error in the readout.
The multiplication can be accomplished readily by dividing the period of the incoming frequency by the multiplicand. A 10 MHZ pulse train is gated by the incoming frequency into a counting circuit. The accumulated pulse count for one period is then divided by the multiplicand (M) and fed into a down counting circuit clocked at 10 MHZ. The resulting output frequency will then be M times greater than the incoming frequency.
The invention also uses a readout which consists of six digits (00000.0). The multiplier, as explained previously, is divided into three decades to reduce resolution error. The reduction in resolution error can be accomplished as follows: whenever a digital readout is used, there is always an uncertainty in the last digit. Using the three decade system, the first decade (30 to 300) has a resolution of +0.1 RPM (0.33% maximum). The second ~ decade (300 to 3,000) has a resolution of +1 RPN (0.33%
; ~ maximUm). The third decade (3,000 to 30,000) has a resolution ; of +~10 RMP (0.33% maximum). The third decade cannot have its resolution reduced to +l RPM without increasing the multiplier quantization error beyond acceptable limits.
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Fin~lly, the system utilizes a comparator and a shut-down actuator. The readout value and thumb wheel switch values can be compared quickly and easily utilizing digital circuitry. If the readout value exceeds that set on the thumb wheel switches, a latching relay is pulsed, closing a set of contacts to initiate the shut-down sequence.
The maximum delay between overspeed occurrence and shut-down initiation will be one second. Normally, no significant damage to the rotating member e.g. turbine can occur in one second. The latching relay is manually reset once the shut down has been initiated.
To facilitate easy repair and maintenance in the field, the circuits are sub-divided into a number of small boards, each counting from 3 to 5 IC's per board.
Edge connectors can be used to enhance maintenance and repair.
The system described above has been bench tested at the University of Regina, Regina, Saskatchewan, Canada, and has been found to be very successful. The range of the monitor is easily extended and probably can be adapted into a hand-held tachometer by using memory chips, etc.
The system has been found to be reliable and has resulted in a considerable cost saving over the mechanical system previously used at this station.
While particular embodiments of the present invention have been shown and described, it is apparent that various changes and modifications may be made, and it is therefore intended in the following claims to cover all such obvious modifications and changes as may fall withln the true spirit and scope oE this invention.
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The electromagnetic system described above may further 10 include control means connected to the output of the comparison means. The control means are operable for controlling the rotational speed of the rotating object.
The rotational speed of the object is increased if the number of pulses counted by the pulse counting means in the desired time period is less than the pre-selected value. However, if the number of pulses counted by the pulse counting means in the desired time period is greater than the pre-selected value then the control means reduce the rotational speed of the object.
According to another aspect of the invention, there ; is provided hn electromagnetic apparatus operable for measuring and controlling the rotational speed of a rotating ; object, comprising in combination the following:
(a) A continuous wave Doppler transceiver comprising a radar frequency electromagnetic transmitter and a radar fre~uency electromagnetic Feceiver. The transmitter is operable to transmit a radar frequency electromagnetic signal towards the rota~ing object via an antenna system. The receiver is operable to to receive at least a portion of the signal reflected ~i - 6a -from the rotating object. The reflected signal is mixed with a portion o~ the transmitted signal in the receiver so as to generate an output audio frequency electrical signal whose period is inversely proportional to the rotational speed of the rotating object.
(b) A low noise electronic amplifier coupled to the output of the transceiver for amplifying the magnitude of the output audio signal of the transceiver.
(c) Wave shaper means connected to the output of the amplifier for generating a train of electrical pulses.
An integer number of pulses corresponds to each revolution of the rotating object.
(d) Frequency multiplier means are connected to the output of the wave shaper means for multiplying the pulse repetition rate of the pulse train which appears at the output of the wave shaper means. The pulse repetition rate of the pulse train is multiplied by a second integer and thereby reduces the time required to make a measurement of the rotational speed of the -~
rotating object. The output pulse train from the ~ frequency multiplier means has a pulse repetition rate ; exceeding the pulse repetition rate of the input pulse train by a fa~tor equal to the second integer.
(e) Digital readout means, connected to the output of the frequency multiplier means for counting the number of pulses at the output of the frequency multiplier means in a desired period of time and thereby providing an indication of the number of revolutions of the rotating object in the desired period of time.
_ ~ - 6b -~ .
,. ' ~ , . ., . ., - . : :': .
(f) Comparison mear.s coupled to the readout means operable for comparing the number of revolutions of the rotating object in the desired period of time with a predetermined number.
(g) Control means connected to the comparison means for controlling the rotational speed of the rotating object.
In the system described above, the frequency multiplier means may comprise:
(a) First means for generating a first pulse train of known pulse repetition rate and period.
(b) Second means, coupled to the first pulse train generating means, for generating a second pulse train having a pulse repetition rate equal to the known pulse repetition rate of the first pulse train multiplied by the reciprocal of the second integer.
(c) Means for gating the second pulse train by the input pulse train to the frequency multiplier means.
(d) Counting means, coupled to the output of the gating means, for counting the number of pulses output from the gating means during a selected period of time corresponding to the period of the input pulse train.
(e) A down counting aircuit, coupled to the output of the counting means, the down counting circuit being clocked at the ~irst pulse train repetition rate, the output pulse train o~ the down counting circuit, being the output pulse train of the frequency multiplier means, having a pulse rate exceeding that of the input pulse train by a multiplicand equal to the second integer.
. -, :.,.. . ~ ', .- - ' . :
_ WINGS
In the drawings:
FIGURE 1 represents a block diagram of a digital readout tachometer.
DETAILED DESCRIPTION OF THE INVENTION_ A transceiver, while mainly used in the past for the measurement of linear velocities, is utilized for the measurement of rotational velocities. The module transmits a microwave signal, and mi~es the signal reflected from a linearly moving or rotationally moving object to produce an audio signal whose period is inversely proportional to either the linear or the rotational speed of the object being observed. This signal is then processed by analog and digital circuitry to give the desired readout.
For angular velocity measurement, the transceiver is used to detect discontinuities on the surface of the rotating member, e.g., shaft surface. Even minute discon-tinuities on a rotating member have been shown to produce audio signals. Using a 3 mW transceiver, signals of the order of tens of mV- peak have been measured from a machined shaft and in the order of tens ofJuV-peak from a rotating he~a~onal nut.
The main advantage of using a Doppler transceiver system is that it is non-contacting. The rotating member e.g. turbine shaft, does not have to drive any mechanisms, and no modifications have to be made to the member, that is, the attachment of magnets or reflective tape. The output of the transceiver merely has to be directed onto the member via a horn, or other antenna system, and shielded to prevent the movement of objects other than the member :
' .. .. , : ' ` ~ ~ ' ' being monitored from affecting the transceivers electromagnetic field and introducing extraneous signals. The economics of using a Doppler transceiver also make it attractive over other RPM measuring devices available on the market.
Since the receiver detects discontinuities on the rotating surface, the only real disadvantage of this system is that the readout may be a multiple of the actual velocity of the rotating member. This problem is easily overcome by using analog circuitry to eliminate the lower level discontinuity si~nals and then using digital circuitry to eliminate whatever harmonics are left. However, the unit must be individually calibrated for each shaft to be monitored.
As shown in Figure 1 (which shows a block diagram of the digital readout tachometer) the audio output of the Doppler transceiver is amplified and is then fed into the wave shaper which eliminates the harmonics as described previously, and makes the signal compatible with the logic being used. The signal is then multiplied by a digital frequency multiplier and is fed into a readout. The fre~uency of the signal being fed into the readout is monitored by a comparator. If this frequency exceeds a predetermined set point, the comparator produces a pulse which is used to activate the turbines speed control circuitry.
TTL was used to construct the logic, however other types of logics such as CMOS could also have been used. It is also conceivable that a CPU could have been used in place of the logic.
The Doppler transceiver that has been used is a preconstructed microwave device that is now commonly .
., .... ,. . , , . ~
available on the electronics market-place. The Doppler transceiver transmits a signal in the 10 GHz region, receives the reflected signal and mixes the signals to produce an audio signal whose frequency is proportional to the linear or rotational speed of the moving or rotating body at which its transmitted beam is directed, and is also proportional to the number of discontinuities on the surface of the rotating body. Even minute surface discontinuities produce measurable audio signals.
A low noise amplifying circuit is required since the output signal of the Doppler transceiver unit in some cases may be quite small (10uV peak). Once the signal is amplified to SV peak, it is readily shaped for TTL
compatibility using a one shot and is reduced to its fundamental harmonic by a frequency divider circuit.
Any frequency Doppler module may be used.
The system also uses an amplifier/wave shaper which produces one pulse per revolution of the rotating member e.g. turbine shaft. To obtain a readout in revolutions per minute, it would normally be necessary to count pulses for one minute. This is a rather long and impractical counting time and was considered by the inventors to be potentially detrimental. This was so because any circuit used to detect excessive speed of the member e.g. turbine shaft (overspeed detector) would be connected to the counting circuit and there was therefore the possibility of the turbine, for example, running a full minute at an excessive and possibly dangerous speed before the shut down sequence would be initiated. A more reasonable solution would be to count for only one second, thus requiring an x60 multiplier.
~ . :
A computerized study showed that it would be best to divide the meter range into three decades, 30 to 300, 300 to 3,000 and 3,000 to 30,000 RPM. The multiplier was assigned a different multiplicand for each decade: 600 for 30 to 300, 60 for 300 to 3,000 and 6 for 3,000 to 30,000. The result of this decadization was to assure a maximum quantitization error of 0.1 percent in the multiplier. This technique also reduced the resolution error in the readout.
The multiplication can be accomplished readily by dividing the period of the incoming frequency by the multiplicand. A 10 MHZ pulse train is gated by the incoming frequency into a counting circuit. The accumulated pulse count for one period is then divided by the multiplicand (M) and fed into a down counting circuit clocked at 10 MHZ. The resulting output frequency will then be M times greater than the incoming frequency.
The invention also uses a readout which consists of six digits (00000.0). The multiplier, as explained previously, is divided into three decades to reduce resolution error. The reduction in resolution error can be accomplished as follows: whenever a digital readout is used, there is always an uncertainty in the last digit. Using the three decade system, the first decade (30 to 300) has a resolution of +0.1 RPM (0.33% maximum). The second ~ decade (300 to 3,000) has a resolution of +1 RPN (0.33%
; ~ maximUm). The third decade (3,000 to 30,000) has a resolution ; of +~10 RMP (0.33% maximum). The third decade cannot have its resolution reduced to +l RPM without increasing the multiplier quantization error beyond acceptable limits.
i 10 .
- ::
Fin~lly, the system utilizes a comparator and a shut-down actuator. The readout value and thumb wheel switch values can be compared quickly and easily utilizing digital circuitry. If the readout value exceeds that set on the thumb wheel switches, a latching relay is pulsed, closing a set of contacts to initiate the shut-down sequence.
The maximum delay between overspeed occurrence and shut-down initiation will be one second. Normally, no significant damage to the rotating member e.g. turbine can occur in one second. The latching relay is manually reset once the shut down has been initiated.
To facilitate easy repair and maintenance in the field, the circuits are sub-divided into a number of small boards, each counting from 3 to 5 IC's per board.
Edge connectors can be used to enhance maintenance and repair.
The system described above has been bench tested at the University of Regina, Regina, Saskatchewan, Canada, and has been found to be very successful. The range of the monitor is easily extended and probably can be adapted into a hand-held tachometer by using memory chips, etc.
The system has been found to be reliable and has resulted in a considerable cost saving over the mechanical system previously used at this station.
While particular embodiments of the present invention have been shown and described, it is apparent that various changes and modifications may be made, and it is therefore intended in the following claims to cover all such obvious modifications and changes as may fall withln the true spirit and scope oE this invention.
~ .
Claims (27)
1. A method of measuring, controlling and monitoring the rotational speed of a rotating member comprising employing a Doppler effect transceiver to measure the rotation speed of the rotating member, feeding the signal from the Doppler transceiver into an amplifier, subsequently into a wave shaper, subsequently into a digital multiplier, subsequently into a readout and comparator, and finally into control circuitry which, if the rotational speed of the member exceeds a predetermined speed, shuts down the member.
2. A method of measuring, monitoring and controlling the rotational shaft speed of a turbine by utilizing a Doppler transceiver which detects discontinuities on the surface of the rotating shaft of the turbine, whereby the audio output of the doppler transceiver is amplified and is then fed into a wave shaper which eliminates the harmonics, renders the signal compatible with logic being used in the system, the signal being multiplied by a digital frequency multiplier and being fed into a readout, the frequency of the signal being fed into the readout whereby it is monitored by a comparator, and if the frequency exceeds a predetermined set point, the comparator produces a pulse which is utilized to activate speed control circuitry attached to the turbine.
Page 1 of Claims
Page 1 of Claims
3. The method according to claim 2 wherein a 3 milliwatt transceiver is used.
4. The method of claim 3 wherein the output of the transceiver is directed onto the rotating shaft by a horn, or an antenna system, and is shielded to prevent the movement of objects other than the rotating shaft being monitored from affecting the transceiver's electro-magnetic field.
5. A method of determining the rate of rotation of a rotating object comprising utilizing an electronic measuring means based on the Doppler effect for transmitting a signal for reflection off a rotating object and receiving the signal reflected from the rotating object and mixing the signal to produce an audio signal with a frequency proportional to the rotational speed of the rotating body.
6. The method of claim 5 wherein the output signal from the Doppler measuring unit is amplified to 5 V peak whereby it is easily shaped for TTL compatibility using a one shot and is reduced to a fundamental harmonic by a frequency divider circuit.
7. The method of claim 6 wherein amplifier/wave shaper means are utilized to produce one pulse per revolution and such pulses are counted for one second utilizing an X 60 multiplier means.
Page 2 of Claims
Page 2 of Claims
8. The method of claim 7 whereby multiplication is accomplished by dividing the period of the incoming frequency by the multiplicand, a 10 MHz pulse train being gated by the incoming frequency into a counting circuit, the accumulated pulse count for one period being then divided by the multiplicand and being fed into a down counting circuit clocked at 10 MHz, the resulting output frequency thus being greater according to the multiplicand ratio than the incoming frequency.
9. The method of claim 8 whereby a digital readout means is used such that the multiplier is divided into three decades to reduce resolution error.
10. The method of claim 9 wherein the readout value is compared with a thumb wheel switch means value preset by means of digital circuitry, and when the readout value exceeds the value set on the thumb wheel switch, a latch relay means is pulsed which in turn closes a set of contacts to shut down the rotating object.
11. An electromagnetic system operable for measuring, and monitoring the rotational speed of a rotating object comprising in combination (1) a continuous wave Doppler transceiver operable to transmit an electromagnetic signal towards the rotating object, said Doppler transceiver being operable to receive an electromagnetic signal reflected from the rotating object and producing an audio frequency output electrical signal, the period of which signal is inversely proportional to the rotational speed of the rotating object;
Page 3 of Claims (2) amplifier and wave shaper means which receive the audio frequency output electrical signal from said Doppler transceiver for generating a train of electrical pulses;
(3) multiplication means for increasing the pulse repetition rate of said pulse train;
(4) pulse counting means for counting the total number of pulses output from said multiplication means in a desired time period;
(5) comparison means for comparing the total number of pulses counted in a given period of time with a pre-selected value.
Page 3 of Claims (2) amplifier and wave shaper means which receive the audio frequency output electrical signal from said Doppler transceiver for generating a train of electrical pulses;
(3) multiplication means for increasing the pulse repetition rate of said pulse train;
(4) pulse counting means for counting the total number of pulses output from said multiplication means in a desired time period;
(5) comparison means for comparing the total number of pulses counted in a given period of time with a pre-selected value.
12. The system of claim 11 wherein the transceiver is a 3 milliwatt transceiver.
13. The system of claim 12 wherein the amplifier and wave shaper means produces one pulse per rotation of the rotating object.
14. The system of claim 13 wherein the multiplication means increases the pulse rate of the pulse train output from the amplifier and wave shaper means by a factor of 60.
15. The system of claim 11 wherein a shut down actuator is incorporated into the system.
15. The system of claim 11 wherein a shut down actuator is incorporated into the system.
15. The system of claim 13, 14 or 15 wherein circuits are sub-divided into boards counting 3 to 5 IC's per board.
Page 4 of Claims
17. The system of claim 11 further including (6) control means connected to the output of said comparison means operable for controlling the rotational speed of the rotating object, said control means being operable for increasing the rotational speed of the object if the number of pulses counted by said pulse counting means in said desired time period is less than said pre-selected value, and said control means being operable for reducing the rotational speed of the object if the number of pulses counted by said pulse counting means in the desired time period is greater than said pre-selected value.
18. The system of claim 11 further including (7) control means connected to the output of said comparison means operable for pulsing a latching relay to initiate a shut down sequence to cause a rotating object to cease rotating if the total number of pulses counted by said pulse counting means in said desired time period exceeds said pre-selected value.
19. An electromagnetic apparatus operable for measuring and contolling the rotational speed of a rotating object, comprising in combination:
(a) a continuous wave doppler transceiver comprising a radar frequency electromagnetic transmitter and a radar frequency electro-magnetic receiver, said transmitter being operable to transmit a radar frequency electromagnetic signal towards the rotating object via an antenna system, said receiver being operable to receive at least a portion of the signal reflected from the rotating Page 5 of Claims object, wherein the received reflected signal is mixed with a portion of the transmitted signal to generate an output audio frequency electrical signal whose period is inversely proportional to the rotational speed of the rotating object;
(b) a low noise electronic amplifier coupled to the output of said transceiver for amplifying the magnitude of the output audio signal of said transceiver;
(c) waveshaper means connected to the output of said amplifier for generating a train of electrical pulses, an integer number of pulses corresponding to each revolution of the rotating object;
(d) frequency multiplier means connected to the output of said waveshaper means for multiplying the pulse repetition rate of the pulse train, which pulse train appears at the output of said waveshaper means, by a second integer and thereby reducing the time to make a measurement of the rotational speed of the rotating object, the output pulse train from said frequency multiplier means having a pulse repetition rate exceeding the pulse repetition rate of the input pulse train by a factor equal to said second integer;
(e) digital readout means, connected to the output of said frequency multiplier means, for counting the number of pulses at the output of said frequency multiplier means in Page 6 of Claims a desired period of time and thereby being operable for obtaining an indication of the number of revolutions of the rotating object in said desired period of time;
(f) comparison means coupled to said readout means operable for comparing the number of revolutions of the rotating object in said desired period of time with a predetermined number; and (g) control means connected to said comparison means operable for controlling the rotational speed of the rotating object.
(a) a continuous wave doppler transceiver comprising a radar frequency electromagnetic transmitter and a radar frequency electro-magnetic receiver, said transmitter being operable to transmit a radar frequency electromagnetic signal towards the rotating object via an antenna system, said receiver being operable to receive at least a portion of the signal reflected from the rotating Page 5 of Claims object, wherein the received reflected signal is mixed with a portion of the transmitted signal to generate an output audio frequency electrical signal whose period is inversely proportional to the rotational speed of the rotating object;
(b) a low noise electronic amplifier coupled to the output of said transceiver for amplifying the magnitude of the output audio signal of said transceiver;
(c) waveshaper means connected to the output of said amplifier for generating a train of electrical pulses, an integer number of pulses corresponding to each revolution of the rotating object;
(d) frequency multiplier means connected to the output of said waveshaper means for multiplying the pulse repetition rate of the pulse train, which pulse train appears at the output of said waveshaper means, by a second integer and thereby reducing the time to make a measurement of the rotational speed of the rotating object, the output pulse train from said frequency multiplier means having a pulse repetition rate exceeding the pulse repetition rate of the input pulse train by a factor equal to said second integer;
(e) digital readout means, connected to the output of said frequency multiplier means, for counting the number of pulses at the output of said frequency multiplier means in Page 6 of Claims a desired period of time and thereby being operable for obtaining an indication of the number of revolutions of the rotating object in said desired period of time;
(f) comparison means coupled to said readout means operable for comparing the number of revolutions of the rotating object in said desired period of time with a predetermined number; and (g) control means connected to said comparison means operable for controlling the rotational speed of the rotating object.
20. The system of claim 19 wherein said transmitter transmits signals in the 10 GHz region and has an output power level of about 3 milliwatts.
21. The system of claim 19 wherein said antenna system is a horn, said horn being shielded from extraneous signals.
22. The system of claim 19 wherein each pulse output from said waveshaper means corresponds to a single revolution of the rotating object and said integer is unity.
23. The system of claim 19 wherein said waveshaper means includes a one shot circuit.
24. The system of claim 19 wherein said second integer by which said frequency multiplier means multiplies the pulse rate of the pulse train is 60 and wherein said Page 7 of Claims readout means has a three decade range, namely, thirty to three hundred revolutions per minute, three hundred to three thousand revolutions per minute, and three thousand to thirty thousand revolutions per minute.
25. The system of claim 19 wherein said frequency multiplier means comprises:
(a) first means for generating a first pulse train of known pulse repetition rate and period;
(b) second means, coupled to said first pulse train generating means, for generating a second pulse train having a pulse repetition rate equal to said known pulse repetition rate of said first pulse train multiplied by the reciprocal of said second integer;
(c) means for gating said second pulse train by the input pulse train to said frequency multiplier means;
(d) counting means, coupled to the output of said gating means, for counting the number of pulses output from said gating means during a selected period of time corresponding to the period of said input pulse train; and (e) a down counting circuit, coupled to the output of said counting means, said down counting circuit being clocked at said first pulse train repetition rate, the output pulse train of said down counting circuit, being the output pulse train of said frequency Page 8 of Claims multiplier means, having a pulse rate exceeding that of the input pulse train by a multiplicand equal to said second integer.
(a) first means for generating a first pulse train of known pulse repetition rate and period;
(b) second means, coupled to said first pulse train generating means, for generating a second pulse train having a pulse repetition rate equal to said known pulse repetition rate of said first pulse train multiplied by the reciprocal of said second integer;
(c) means for gating said second pulse train by the input pulse train to said frequency multiplier means;
(d) counting means, coupled to the output of said gating means, for counting the number of pulses output from said gating means during a selected period of time corresponding to the period of said input pulse train; and (e) a down counting circuit, coupled to the output of said counting means, said down counting circuit being clocked at said first pulse train repetition rate, the output pulse train of said down counting circuit, being the output pulse train of said frequency Page 8 of Claims multiplier means, having a pulse rate exceeding that of the input pulse train by a multiplicand equal to said second integer.
26. The system of claim 25 wherein:
(i) said second integer by which said frequency multiplier means multiplies the input pulse rate of the input pulse train is 600, 60 or 6 and wherein said readout means has a three decade range, namely, thirty to three hundred revolutions per minute, three hundred to three thousand revolutions per minute, and three thousand to thirty thousand revolutions per minute;
(ii) each pulse output from said waveshaper means corresponds to a single revolution of the rotating object and said integer is unity;
(iii) said predetermined number employed in said comparison means is provided by means of thumb wheel switches which provide a maximum rotational speed reference; and (iv) said control means is operable for transmitting a pulse to a latching relay if the rotational speed of the rotating object as indicated by said digital readout means exceeds the value set on the thumb wheel switches whereby a shut-down sequence is initiated to prevent the further flow of motive power to the rotating object.
Page 9 of Claims
(i) said second integer by which said frequency multiplier means multiplies the input pulse rate of the input pulse train is 600, 60 or 6 and wherein said readout means has a three decade range, namely, thirty to three hundred revolutions per minute, three hundred to three thousand revolutions per minute, and three thousand to thirty thousand revolutions per minute;
(ii) each pulse output from said waveshaper means corresponds to a single revolution of the rotating object and said integer is unity;
(iii) said predetermined number employed in said comparison means is provided by means of thumb wheel switches which provide a maximum rotational speed reference; and (iv) said control means is operable for transmitting a pulse to a latching relay if the rotational speed of the rotating object as indicated by said digital readout means exceeds the value set on the thumb wheel switches whereby a shut-down sequence is initiated to prevent the further flow of motive power to the rotating object.
Page 9 of Claims
27. The system of claim 26 wherein:
(i) said antenna system is a horn, said horn being shielded from extraneous signal; and (ii) said transmitter transmits signals in the 10 GHz region and has an output power level of about 3 milliwatts; and (iii) said waveshaper means includes a one shot circuit.
(i) said antenna system is a horn, said horn being shielded from extraneous signal; and (ii) said transmitter transmits signals in the 10 GHz region and has an output power level of about 3 milliwatts; and (iii) said waveshaper means includes a one shot circuit.
Priority Applications (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA293,494A CA1111941A (en) | 1977-12-20 | 1977-12-20 | Turbine rotational speed measurement and control utilizing a x-band doppler transceiver |
| GB7848713A GB2011752A (en) | 1977-12-20 | 1978-12-15 | Method and apparatus for contactless rotational speed measurement |
| DE19782854432 DE2854432A1 (en) | 1977-12-20 | 1978-12-16 | METHOD AND SYSTEM FOR MEASURING THE ROTATIONAL SPEED OF ROTATING PARTS |
| FR7835756A FR2412845A1 (en) | 1977-12-20 | 1978-12-20 | ELECTROMAGNETIC SYSTEM FOR ADJUSTING AND CONTROLLING THE ROTATION SPEEDS OF VARIOUS OBJECTS |
| IT52381/78A IT1109235B (en) | 1977-12-20 | 1978-12-20 | X-RATE SPEED MEASURING AND CONTROL DEVICE USING A RICETRAS X-BAND DOPPLER-EFFECT RECEIVER |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA293,494A CA1111941A (en) | 1977-12-20 | 1977-12-20 | Turbine rotational speed measurement and control utilizing a x-band doppler transceiver |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1111941A true CA1111941A (en) | 1981-11-03 |
Family
ID=4110338
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA293,494A Expired CA1111941A (en) | 1977-12-20 | 1977-12-20 | Turbine rotational speed measurement and control utilizing a x-band doppler transceiver |
Country Status (5)
| Country | Link |
|---|---|
| CA (1) | CA1111941A (en) |
| DE (1) | DE2854432A1 (en) |
| FR (1) | FR2412845A1 (en) |
| GB (1) | GB2011752A (en) |
| IT (1) | IT1109235B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2322987A (en) * | 1997-03-06 | 1998-09-09 | Marconi Gec Ltd | Object detection in turbine influx or efflux |
| DE19806121C2 (en) * | 1998-02-14 | 2001-10-18 | Rolls Royce Deutschland | Device for determining various pressure values in a rotating system |
| DE19943150A1 (en) * | 1999-09-09 | 2001-03-22 | Siemens Ag | Ore mill and method for operating the ore mill |
| DE10359930A1 (en) * | 2003-01-23 | 2004-08-05 | Siemens Ag | Determining method of the demands on rotating blades in a current machine, blades being fixed or arranged on a rotor shaft |
| US10705198B2 (en) * | 2018-03-27 | 2020-07-07 | Infineon Technologies Ag | System and method of monitoring an air flow using a millimeter-wave radar sensor |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3852743A (en) * | 1970-09-18 | 1974-12-03 | Bendix Corp | Homodyne doppler radar with increased target sensitivity |
-
1977
- 1977-12-20 CA CA293,494A patent/CA1111941A/en not_active Expired
-
1978
- 1978-12-15 GB GB7848713A patent/GB2011752A/en not_active Withdrawn
- 1978-12-16 DE DE19782854432 patent/DE2854432A1/en active Pending
- 1978-12-20 FR FR7835756A patent/FR2412845A1/en not_active Withdrawn
- 1978-12-20 IT IT52381/78A patent/IT1109235B/en active
Also Published As
| Publication number | Publication date |
|---|---|
| FR2412845A1 (en) | 1979-07-20 |
| IT7852381A0 (en) | 1978-12-20 |
| DE2854432A1 (en) | 1979-06-21 |
| IT1109235B (en) | 1985-12-16 |
| GB2011752A (en) | 1979-07-11 |
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