SU877795A1

SU877795A1 - Component piezoelectric pickup

Info

Publication number: SU877795A1
Application number: SU802881139A
Authority: SU
Inventors: Виталий Николаевич Максимов
Original assignee: Таганрогский Радиотехнический Институт
Priority date: 1980-02-11
Filing date: 1980-02-11
Publication date: 1981-10-30

Description

Изобретение относится к технике виброизмерений и технике неразрушающего Контроля, предназначено для исследования перемещений поверхностей по ' _ трем взаимно перпендикулярным осям ^эи может быть использовано в ультразвуковой дефектоскопии для приема продольных, сдвиговых и рэлеевских волн, а также для измерения вибросмещения . _ твердых поверхностей. ^и The invention relates to techniques for vibration measurements and the technique of non-destructive testing, is intended for the study of surface movements along the '_ three mutually perpendicular axes ^e and can be used in ultrasonic inspection for receiving longitudinal, shear and Rayleigh waves, as well as for measuring vibration displacement. _ hard surfaces. ^and

Известны пьезоэлектрические датчики для измерения вибросмещений по какой-либо одной оси. Они состоят из корпуса, пьезоэлементов и инертной массы £1J. 15Piezoelectric sensors are known for measuring vibration displacements along any one axis. They consist of a housing, piezoelectric elements and an inert mass of £ 1J. fifteen

Эти датчики имеют ряд существенных недостатков - сложность конструкции, необходимость использования При обработке снимаемых с них сигналов интегрирующих и других нелинейных це- 20 пей, ухудшающих точность измерения, невозможность регистрации сигнала по двум и более осям, наличие паразитного поперечного эффекта.These sensors have a number of significant drawbacks - the complexity of the design, the need to use integrating and other non-linear circuits when processing the signals removed from them, impairing the measurement accuracy, the impossibility of registering a signal along two or more axes, and the presence of a spurious transverse effect.

Известен также компонентный пьезо- 25 электрический датчик, свободный от перечисленных недостатков, с помощью которых можно регистрировать смещения по нескольким осям. Такой датчик состоит из двух пьезопластин, склеен- 30 ных в одну систему и закрепленных в держателе. Пьезопластины разделены слоем электроиэолятора, а их обкладки подключены через сумматор и вычитающий блок к регистрирующему устройству. При этом с выхода сумматора получаЮт сигнал, пропорциональный сжатию пьеэопластин вдоль оси датчика, ас вычитающего блока - сигнал, характеризующий изгибные деформации датчика деформация сжатия компенсируется . Таким образом, данный датчик регистрирует смещения по двум взаимно перпендикулярным осям. При добавлении к этой системе пластин аналогичной системы, ориентированной в перпендикулярном направлении, датчик дает возможность регистрировать три компоненты поля смещения [2J,A component piezoelectric sensor 25 is also known, free of the above disadvantages, with which it is possible to register displacements along several axes. Such a sensor consists of two piezoelectric plates glued together in one system and fixed in a holder. The piezoelectric plates are separated by a layer of an electric eeolator, and their plates are connected through an adder and a subtracting unit to a recording device. In this case, a signal proportional to the compression of the piezoelectric plates along the axis of the sensor and ac of the subtracting block is received from the adder's output — a signal characterizing the bending deformations of the sensor is compensated for by compression. Thus, this sensor detects displacements along two mutually perpendicular axes. When a similar system oriented in the perpendicular direction is added to the system of plates, the sensor makes it possible to register three components of the bias field [2J,

Однако в то же время датчику присущ ряд существенных недостатков невозможность измерения смещений по * трем осям, сложность конструкции, низкая резонансная частота колебательной системл датчика, так как пьезопластины в нем работают в режиме продольного сжатия и изгиба. Кроме того, обязательными элементами датчика являются сумматор и вычитающий ллок, т.е. элементы, требующие для своей работы дополнительной энергии.However, at the same time, the sensor has a number of significant drawbacks: the impossibility of measuring displacements along three axes, the complexity of the design, and the low resonant frequency of the oscillatory system of the sensor, since the piezoelectric plates in it operate in the longitudinal compression and bending mode. In addition, the required elements of the sensor are an adder and a subtracting lock, i.e. elements requiring additional energy for their work.

Наиболее близким по технической сущности к предлагаемому является компонентный пьезоэлектрический^датчик, содержащий присоединенную к держателю и рычагу круглую пьезопластину с нанесенными на одной из ее сторон четырьмя электродами, попарно расположенными на взаимно перпендикулярных диаметрах симметрично относительно центра Гз].The closest in technical essence to the proposed one is a component piezoelectric transducer containing a round piezoelectric plate attached to the holder and to the lever with four electrodes deposited on one of its sides and arranged in pairs on mutually perpendicular diameters symmetrically with respect to the center of Gz].

Недостаток данного устройства заключается в необходимости использования сумматора и вычитающих блоков, что усложняет конструкцию датчика и требует для его работы потребления дополнительной энергии.The disadvantage of this device is the need to use an adder and subtracting blocks, which complicates the design of the sensor and requires additional energy for its operation.

Цель изобретения - упрощение конструкции компонентного пьезоэлектрического датчика.The purpose of the invention is to simplify the design of a component piezoelectric sensor.

Указанная цель достигается тем, что в пьезоэлектрический датчик введены два дифференциальных переменных конденсатора, а на противоположной стороне пьезопластины размещены идентичные электроды, с обеих сторон пьеэопластины концентрично с ней нанесены идентичные круговые электроды, причем диаметрально противоположные электроды, расположенные на одной сторОце пьезопластины, соединены с крайними пластинами соответствующих дифференциальных переменных конденсаторов, а расположенные на другой стороне соединены попарно между собой и со средними пластинами соответствующих дифференциальных конденсаторов.This goal is achieved by the fact that two differential variable capacitors are introduced into the piezoelectric sensor, and identical electrodes are placed on the opposite side of the piezoelectric plate, identical circular electrodes are concentrically applied to both sides of the piezoelectric plate, and diametrically opposite electrodes located on the same side of the piezoelectric plate are connected to the extreme plates of the corresponding differential variable capacitors, and located on the other side are connected in pairs between each other and with middle plates of the corresponding differential capacitors.

Причем круговые электроды выполнены кольцевыми.Moreover, the circular electrodes are made ring.

На’фиг. 1 представлен предлагав- , май датчик, вид сбоку,* на фиг, 2 разрезы А-А и Б—Б на фиг. 1 со схемой включения.Na’fig. 1 is a view suggesting - May sensor, side view, * in FIG. 2, sections A-A and B-B in FIG. 1 with a switching circuit.

Датчик состоит из пьезопластины 1, установленной одной гранью на держателе 2, на другой грани укреплен рычаг 3*, прижатый в процессе измерений к исследуемой поверхности 4, На гранях пьезопластины расположены по пять jq токопроводящих электродов 5-9 и 10-14, электрода 5 и 10 имеют круговую (коль: цевую.) Форму, а электроды 6-9 и 11-14, например, сегментную и все электроды расположены попарно друг против друга по обеим сторонам пьезопластины. Электроды 11 и 13 соединены со средней пластиной дифференциального конденсатора 15, а электрода 12 и 14 со средней пластиной такого же конденсатора 16. Электрода 6 и 8 соединены с крайними пластинами конденсатора 15, а электроды 7 и 9 с крайними пластинами конденсатора 16.The sensor consists of a piezoelectric plate 1 mounted by one face on the holder 2, a lever 3 * is mounted on the other face, pressed against the test surface 4 during measurements. Five jq conductive electrodes 5-9 and 10-14, electrode 5 and 5 are located on the faces of the piezoelectric plate 10 have a circular (stake: base.) Shape, and electrodes 6-9 and 11-14, for example, segmented and all electrodes are arranged in pairs opposite each other on both sides of the piezoelectric plate. The electrodes 11 and 13 are connected to the middle plate of the differential capacitor 15, and the electrodes 12 and 14 to the middle plate of the same capacitor 16. The electrodes 6 and 8 are connected to the extreme plates of the capacitor 15, and the electrodes 7 and 9 to the extreme plates of the capacitor 16.

Датчик работает следующим образом.The sensor operates as follows.

«О"ABOUT

-,,ι- ,, ι

При деформации материала 4 в положительном направлении оси X часть пьезопластины 1, расположенная между электродами 8 и 13, будет сжиматься, а Часть пьезопластины, расположенная между электродами 6 и 11, будет растягиваться с такой же величиной относительной деформации.When the material 4 deforms in the positive direction of the X axis, the part of the piezoelectric plate 1 located between the electrodes 8 and 13 will be compressed, and the part of the piezoelectric plate located between the electrodes 6 and 11 will stretch with the same relative strain.

Таким образом, заряда между электродами 8, 13 и 6, 11 будут равны по величине,.но противоположны по знаку и соответственно получим, что = -U2· i ’ Электроды 8, 13 и б, 11 соединены электрически последовательно таким образом, что U^=U^-U₂. Следовательно, при деформации материала по оси X напряжение будет пропорционально величи-ι не этой деформации, т.е. будет характеризовать смещение по оси X.Thus, the charges between the electrodes 8, 13 and 6, 11 will be equal in magnitude, but opposite in sign, and accordingly we will get that = -U2 · i 'Electrodes 8, 13 and b, 11 are connected electrically in series so that U ^ = U ^ -U ₂ . Consequently, when the material deforms along the X axis, the stress will be proportional to the magnitude ι of this deformation, i.e. will characterize the offset along the x axis.

Напряжения между электродами 7, 12 и 9, 14 при этом будут близки к нулю и 114=0.The voltage between the electrodes 7, 12 and 9, 14 will be close to zero and 114 = 0.

Напряжение Ug также.будет равно нулю, так как одна половина пьезоплактины при этом будет сжиматься, а другая растягиваться, и заряда, образованные в пьезокерамике, расположенной между электродами 5 и 10, будут взаимно компенсироваться.The voltage Ug will also be zero, since one half of the piezoplactin will be compressed and the other will be stretched, and the charges formed in the piezoceramics located between the electrodes 5 and 10 will be mutually compensated.

Аналогично при деформации материала 4 в направлении оси Y напряжение U4 будет пропорционально величине деформации, а напряжения Ug и Ug будут равны нулю.Similarly, when the material 4 deforms in the direction of the Y axis, the stress U4 will be proportional to the amount of deformation, and the stresses Ug and Ug will be zero.

I При деформации Материала 4 в поХО жительном направлении оси Z все участки пьезопластины 1 будут сжиматься и заряда между эле ктродами б, 11,7, 12, 8, 13и 9, 14 будут иметь одинаковую величину и знак. Следовательно, U. »U₂ и -U₂=0. Аналогично U4 также будет равно нулю. Конденсаторами 15 и 16 выравнивают результирующую чувствительность участков пьезопластины 1, расположенных между электродами 6, 11 и 8, 13, а также 7, 12 и 8, 13 •так, чтобы Ug и ид были равны нулю, при деформациях по оси Z, т.е. ;чтобы Ψ - «а и т.д. Напряжение U, снимаемое с электродов 5 и 10, в этом случае будет пропорционально деформации, происходящей по оси Ζ.I During deformation of Material 4 in the positive direction of the Z axis, all sections of piezoelectric plate 1 will be compressed and the charge between electrodes b, 11.7, 12, 8, 13, and 9, 14 will have the same magnitude and sign. Therefore, U. ”U ₂ and -U ₂ = 0. Similarly, U4 will also be zero. Capacitors 15 and 16 align the resulting sensitivity of the sections of piezoelectric plate 1 located between the electrodes 6, 11 and 8, 13, as well as 7, 12 and 8, 13 • so that Ug and id are equal to zero, with deformations along the Z axis, t. e. ; so that Ψ - “a, etc. The voltage U, taken from the electrodes 5 and 10, in this case will be proportional to the deformation occurring along the оси axis.

Таким образом, рассматриваемый датчик имеет ряд преимуществ по сравнению с имеющимся. Его конструкция значительно проще. При своей работе он не требует каких-либо дополнительных источников энергии. Операции суммирования, и вычитания отдельных составляющих выходных напряжений осуществляются в самой пьезопластине, что позволяет дополнительно повысить точность измерений. Ранее эти операции производились в электронных сумматорах и двух вычитающих блоках, основные параметры которых изменялись в разной степени при изменении температуры, напряжения питания и других де5 .стабилизирующих факторов. Упрощена коммутация пьезопластины датчика с остальной регистрирующей схемой, так как в предлагаемом устройстве во всех трех его выходах один из трех токоведущих проводов может быть заземлен, что улучшает, кроме того, помехозащищенность датчика.Thus, the sensor in question has several advantages over the existing one. Its design is much simpler. During his work, he does not require any additional energy sources. The operations of summing and subtracting the individual components of the output voltages are carried out in the piezoelectric plate itself, which allows to further increase the accuracy of measurements. Previously, these operations were carried out in electronic adders and two subtracting units, the main parameters of which changed to varying degrees with changes in temperature, supply voltage, and other stabilizing factors. The switching of the piezoelectric plate of the sensor with the rest of the recording circuit is simplified, since in the proposed device in all three of its outputs one of the three current-carrying wires can be grounded, which also improves the noise immunity of the sensor.

Claims

The invention relates to a vibration measurement technique and a non-destructive testing technique, is intended for studying surface movements along three mutually perpendicular axes and can be used in ultrasonic flaw detection for receiving forward, shear and Rayleigh waves as well as for measuring the vibration displacement of solid surfaces. Piezoelectric sensors are known for measuring vibration displacements along any one axis. They consist of a body, piezoelectric elements and an inertial mass, 1j,. These sensors have a number of significant drawbacks - design complexity, the need to use integrating and other nonlinear circuits for processing the signals removed from them that degrade measurement accuracy, the inability to record a signal along two or more axes, the presence of a parasitic transverse effect. Also known is a component piezoelectric sensor, free from the listed drawbacks, with which it is possible to register displacements on several axes. Such a sensor consists of two piezoelectric plates glued together in one system and fixed in a holder. Piezoplates are separated by an insulator layer, and their plates are connected through an adder and a subtraction unit to a recording device. In this case, from the output of the adder, a signal is obtained that is proportional to the compression of piezoplates along the sensor axis, and from the subtractor unit — a signal characterizing the deformation of the sensor, the compression deformation is compensated. Thus, this sensor records displacements along two mutually perpendicular axes. When plates are added to this system, similar to the system oriented in the perpendicular direction, the sensor makes it possible to register three components of the displacement field 2 J. However, at the same time significant shortcomings, the impossibility of measuring the displacements on three axes, the complexity of the design, the low resonant frequency of the oscillatory system of the sensor, since the piezoelectric plates in it operate in the mode of initial compression and bending but. In addition, the adder and subtraction unit, i.e. elements requiring additional energy for their work. The closest in technical essence to the present invention is a component piezoelectric sensor containing a circular piezoplate attached to the holder and a lever with four electrodes applied on one of its sides, pairwise placed on mutually perpendicular diameters symmetrically relative to the center Gz. The disadvantage of this device lies in the necessity of using either an adder and a valid block, which complicates the design of the sensor and requires additional energy for its operation. The purpose of the invention is to simplify the design of the component piezoelectric sensor. This goal is achieved by introducing two differential variable capacitors into the piezoelectric sensor, and identical electrode electrodes are placed on the opposite side, identical circular electrodes are placed on both sides of the piezoelectric plate, and diametrically opposed electrodes located on one of the piezoelectric plates, which are diametrically opposed. with the extreme plates of the corresponding differential variable capacitors, and those located on the other side are connected in pairs with each other and with middle plates of the corresponding differential capacitors. . . Moreover, the circular electrodes are annular. FIG. 1 shows the proposed sensor, side view; FIG. 2, sections A-A and B-B in FIG. 1 with a wiring diagram. The sensor consists of a piezoplate 1 installed by one face on the holder 2, on the other face a lever 3 is fixed, pressed in the process of measurements to the surface 4, on the faces of the piezoplates the plates are located along the tons. conductive electrodes 5-9 and 10-1, electrodes 5 and 10 are circular (ring shaped, and electrodes 6-9 and 11-1, for example, the segment electrode and all electrodes are arranged in pairs against each other on both sides of the piezoelectric plate. Electrodes 11 and 13 connected to the middle plate of the differential capacitor 15, and electrodes 12 and 14 to the middle plate of the same capacitor 16. Electrodes 6 and 8 are connected to the outer plates of the capacitor 15, and electrodes 7 and 9 to the outer plates of the capacitor 16. The sensor works as follows material 4 in put The direction of the X axis of the piezoplate 1, located between electrode B and 13, will be compressed, and the tJacTb piezo plate, located between electrodes 6 and 11, will stretch with the same amount of relative deformation. Thus, the charge between electrodes 8 , 13 and b, 11 will be equal in magnitude, opposite in sign and, accordingly, we obtain -U2. The electrodes 8, 13 and 6, 11 are electrically connected in series in such a way that Consequently, when the material is deformed along the X axis, the voltage proportionally not this deformations, i.e. will characterize the displacement along the X axis. The voltages between the electrodes 7, 12, and 9, 14, in this case, will be close to zero and. The voltage Ug- will also be zero, since one half of the piezo is (the joints will be compressed and the other will be stretched, and the charges formed in the piezoceramic located between electrodes 5 and 10 will be mutually compensated. Similarly, during deformation Material 4 in the spacing of the Y axis, the voltage u4 will be proportional to the magnitude of the deformation, and the voltages U and 1) will be zero. During the deformation of the Material 4 in the no-z direction of the Z axis, all portions of the piezoplate 1 will be compressed and the charges between the electrodes 6, 11.7, 12, 8, 13 and 9, 14 will have the same magnitude and sign. Therefore, and. U / ji and and. Similarly, 114 will also be zero. The capacitors 15 and 16 equalize the resulting sensitivity of the sections of the piezoplates if located between electrodes 6, 11 and 8, 13, as well as 7, 12 and 8, 13 so that the ultrasonic and U4 are equal to zero, with deformations along the Z axis, i.e. . to 0 I am etc. The voltage U taken from electrodes 5 and 10 in this case will be proportional to the strain occurring along the Z axis. Thus, the sensor in question has a number of advantages compared with just that. Its construction is much simpler. In his work, he does not require any additional sources of energy. The operations of summation and subtraction of individual components to the output output stresses are carried out in the pieoplastin itself, which makes it possible to further increase the accuracy of measurements. Previously, these operations were carried out in electronic adders and two subtracting units, the main parameters of which were in varying degrees when the temperature of the supply voltage and others changed to stabilizing factors. The switching of the sensor pieoplastics with the rest of the recording circuit is simplified, since in the proposed device, all of its three outlets one of the three current-carrying wires can be grounded, which improves, in addition, the noise immunity of the sensor. Claim 1. A component piezoelectric sensor comprising a circular piezoelectric plate attached to the holder and a lever with four electrode electrodes arranged on one and its sides, arranged in pairs with mutually perpendicular diameters p11Bx diametrically with respect to the center, distinguished by the fact that G is the purpose of simplification constructions, two differential variable capacitors are introduced into it, and on the opposite side of the piezoelectric plates identical electrodes are placed on both sides of the piezoplates, which are concentrically applied with it identical circular electrodes, with diametrically opposite electrodes located on one side of the piezoplates, connected to the extreme plates of the respective differential variable capacitors, and those located on the other side are connected in pairs to each other and to the middle plates of the corresponding differential capacitors. 2. The sensor according to claim 1, characterized in that the circular electrodes are annular. Sources of information taken into account in the examination 1. Klyukin II, Kolesnikov A.Ye. Acoustic measurements in shipbuilding. L., Shipbuilding, 1966, p. 21.

2. The author's certificate of the USSR 210503, cl. B 06 B 1/06, 1968.

3. USSR author's certificate according to the application No. 2758244 / 18-28, cl. H 04 R 17/00, 1979 (prototype).