Thick film integrated LVDT (Linear Variable Differential Transformer) signal regulator

Abstract

A thick film integrated LVDT signal regulator comprises a metal fully-sealed tube shell and a ceramic substrate, the ceramic substrate is a thick film ceramic substrate and is sintered on the tube shell, the ceramic substrate is provided with a gold conduction band, and an excitation generation circuit, a demodulation circuit and a voltage reference circuit are arranged in the tube shell. The excitation generation circuit comprises a rail-to-rail operational amplifier U2A, a power operational amplifier U5, resistors R1-R13 and capacitors C1-C6; the demodulation circuit comprises operational amplifiers U3A, U7A and U7B, high-precision operational amplifiers U4A and U4B, a field efficiency tube T1, diodes D1 and D2, resistors R14-R31 and capacitors C10-C11. The beneficial effects are that the circuit is high in linearity, small in output ripple, low in temperature drift, high in frequency response precision, low in manufacturing cost, simple in design and manufacturing technology, and capable of realizing localization and satisfying use requirements.

Description

Technical Field

[0001] The utility model relates to a signal processor, in particular to a thick film integrated LVDT signal regulator. Background Art

[0002] An LVDT (Linear Variable Differential Transformer) is a linear displacement sensor. Its operating principle is simply that of a movable core transformer. Its input is the mechanical movement of the magnetic core, and its output is an AC voltage signal proportional to the core's position. An LVDT consists of a primary coil and two secondary coils. The primary coil is excited by an external reference sinusoidal signal source, and the two secondary coils are connected in series in opposite directions. The movement of the movable core alters the coupling flux between the primary coils, generating two AC voltage signals of varying amplitudes. The output voltage of the series-connected secondary coils increases as the core moves away from its center position. The phase of the output voltage can be measured to determine the direction of core movement. The LVDT sensor and LVDT signal conditioner are the modulator and demodulator, respectively. Existing LVDT signal conditioners are large-scale integrated circuits (ICs), which are highly integrated, complex to design and manufacture, and have limited market resources, resulting in limited use. Utility Model Content

[0003] The technical problem to be solved by the utility model is to provide a thick film integrated LVDT signal conditioner with low manufacturing cost, simple design and manufacturing process, and capable of meeting use requirements.

[0004] The technical solution of the utility model is: a thick film integrated LVDT signal conditioner, including a metal fully sealed tube shell, a ceramic substrate, the ceramic substrate is a thick film ceramic substrate and is sintered on the tube shell, the ceramic substrate is provided with a gold conduction band, and an excitation generating circuit, a demodulation circuit and a voltage reference circuit are provided in the tube shell. The voltage reference circuit includes a reference voltage chip U1, capacitors C8 and C9. Its special features are:

[0005] The excitation generating circuit includes a rail-to-rail operational amplifier U2A, a power operational amplifier U5, resistors R1-R13, and capacitors C1-C6, wherein the rail-to-rail operational amplifier U2A, resistors R1-R4, capacitors C1 and C6 generate a triangular wave signal with a bias of 5V, which is filtered by a first low-pass filter composed of resistor R5 and capacitor C2, and then passes through resistor R6. One path is isolated by capacitor C3 and then input to the reverse input terminal of the power operational amplifier U5 through resistor R9; a voltage divider circuit composed of resistors R8, R11 and R12 superimposes a 5V bias signal on the reverse input terminal of the power operational amplifier U5; the other path passes through resistor R7 and then passes through a second low-pass filter composed of resistor R10 and capacitor C5 for filtering, and then is differentially amplified by the power operational amplifier U5 to convert it into a sinusoidal wave signal with a certain driving capability, and then the sinusoidal signal is isolated by capacitor C4 to finally provide an excitation signal to the primary side Y1 of the sensor, and the modulation signal is output by the two secondary sides F1 and F2 of the sensor coil;

[0006] The demodulation circuit includes operational amplifiers U3A, U7A and U7B, high-precision operational amplifiers U4A and U4B, field-effect transistor T1, diodes D1 and D2, resistors R14-R31, and capacitors C10-C11. The two sinusoidal wave signals of different sizes generated by the secondary sides F1 and F2 of the sensor are differentially amplified through resistors R14-R19 and the operational amplifier U3A; one path is input to the drain of the field-effect transistor T1 and the non-inverting input terminal of the operational amplifier U7B through resistor R21, and the square wave signal output by the operational amplifier U7A is input to the gate of the J-type field-effect transistor T1 through the DC blocking capacitor C7, the reverse diode D1, resistors R26 and R27. When the J-type field-effect transistor T1 is working normally, the waveform of the drain is the demodulated signal waveform, which is a half-wave signal of the sine wave. The other path is input to the operational amplifier through resistors R22 and R28. The inverting input terminal of U7B, the resistor R23 is connected between the output terminal and the inverting input terminal of the operational amplifier U7B, the half-wave signal is amplified by the operational amplifier U7B, and then passed through the resistor R24, the low-pass second-order filter composed of the high-precision operational amplifier U4A, the resistor R25, and the capacitor C11 to filter the half-wave signal into a DC voltage signal, and then passed through the resistor R31, the reverse proportional amplifier composed of the high-precision operational amplifier U4B and the resistor R30 to amplify the demodulated DC voltage signal, the capacitor C10 is connected to the output terminal of the high-precision operational amplifier U4A and the junction of the resistors R24 and R25, the negative power supply input terminal of the operational amplifier U3A is connected to the system ground through the resistor R20, and the non-inverting input terminal of the high-precision operational amplifier U4A is connected to the system ground through the resistor R29, which is used to convert the change of the sensor position into the change of the output voltage.

[0007] Furthermore, the resistors R1 to R4 and R13 are surface-mount resistors, the remaining resistors are thick-film resistors, the capacitors C1 to C11 are surface-mount capacitors, the operational amplifier U3A, the operational amplifier U7A and U7B respectively use JEFT input dual operational amplifiers, the JEFT input dual operational amplifier, the reference voltage chip U1, the high-precision dual operational amplifiers U4A and U4B and the rail-to-rail dual operational amplifier U2A are bonded to the ceramic substrate with insulating glue, the bottom surfaces of the diodes D1 and D2 are negative electrodes and are bonded to the corresponding gold conduction strips with the drain of the J-type field-effect transistor T1 with conductive glue, the back of the power operational amplifier U5 is welded to the ceramic substrate, the inner lead gold wire is used to connect each chip and the corresponding gold conduction strip, and the outer lead gold wire is used to connect the corresponding gold conduction strip and the tube shell pin.

[0008] The beneficial effects of the utility model are: the circuit has high linearity, small output ripple, low temperature drift and high frequency response accuracy, low production cost, simple design and production process, can be domestically produced, and meets use requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a circuit structure diagram of the utility model;

[0010] Figure 2 It is a schematic diagram of the structure of the utility model;

[0011] Figure 3 yes Figure 2 (without the tube shell) top view.

[0012] Figure 2 and Figure 3 Middle: 1. Gold conduction strip, 2. Resistors, 3. JEFT-input dual operational amplifier, 4. Voltage reference chip, 5. High-precision dual operational amplifier, 6. Rail-to-rail dual operational amplifier, 7. Power operational amplifier, 8. Diode, 9. J-type field-effect transistor, 10. Surface-mount resistor, 11. Surface-mount capacitor, 12. Case pins, 13. Case, 14. Ceramic substrate, 15. Gold wire for inner leads, 16. Gold wire for outer leads. DETAILED DESCRIPTION

[0013] like Figure 1 As shown, a thick film integrated LVDT signal conditioner includes an excitation generating circuit, a demodulation circuit and a voltage reference circuit;

[0014] The voltage reference circuit includes a high-precision reference voltage chip U1, capacitors C8 and C9;

[0015] The excitation generating circuit includes a rail-to-rail operational amplifier U2A, a power operational amplifier U5, resistors R1-R13, and capacitors C1-C6, wherein the rail-to-rail operational amplifier U2A, resistors R1-R4, capacitors C1 and C6 generate a triangular wave signal with a bias of 5V, which is filtered by a first low-pass filter composed of resistor R5 and capacitor C2, and then passes through resistor R6. One path is isolated by capacitor C3 and then input to the reverse input terminal of the power operational amplifier U5 through resistor R9; a voltage divider circuit composed of resistors R8, R11 and R12 superimposes a 5V bias signal on the reverse input terminal of the power operational amplifier U5; the other path passes through resistor R7 and then passes through a second low-pass filter composed of resistor R10 and capacitor C5 for filtering, and then is differentially amplified by the power operational amplifier U5 to convert it into a sinusoidal wave signal with a certain driving capability, and then the sinusoidal signal is isolated by capacitor C4 to finally provide an excitation signal to the primary side Y1 of the sensor, and the modulation signal is output by the two secondary sides F1 and F2 of the sensor coil;

[0016] The demodulation circuit includes operational amplifiers U3A, U7A and U7B, high-precision operational amplifiers U4A and U4B, field-effect transistor T1, diodes D1 and D2, resistors R14-R31, and capacitors C10-C11. The two sinusoidal wave signals of different sizes generated by the secondary sides F1 and F2 of the sensor are differentially amplified through resistors R14-R19 and the operational amplifier U3A; one path is input to the drain of the field-effect transistor T1 and the non-inverting input terminal of the operational amplifier U7B through resistor R21, and the square wave signal output by the operational amplifier U7A is input to the gate of the J-type field-effect transistor T1 through the DC blocking capacitor C7, the reverse diode D1, resistors R26 and R27. When the J-type field-effect transistor T1 is working normally, the waveform of the drain is the demodulated signal waveform, which is a half-wave signal of the sine wave. The other path is input to the operational amplifier through resistors R22 and R28. The inverting input terminal of U7B, the resistor R23 is connected between the output terminal and the inverting input terminal of the operational amplifier U7B, the half-wave signal is amplified by the operational amplifier U7B, and then passed through the resistor R24, the low-pass second-order filter composed of the high-precision operational amplifier U4A, the resistor R25, and the capacitor C11 to filter the half-wave signal into a DC voltage signal, and then passed through the resistor R31, the reverse proportional amplifier composed of the high-precision operational amplifier U4B and the resistor R30 to amplify the demodulated DC voltage signal, the capacitor C10 is connected to the output terminal of the high-precision operational amplifier U4A and the junction of the resistors R24 and R25, the negative power supply input terminal of the operational amplifier U3A is connected to the system ground through the resistor R20, and the non-inverting input terminal of the high-precision operational amplifier U4A is connected to the system ground through the resistor R29, which is used to convert the change of the sensor position into the change of the output voltage.

[0017] like Figure 2As shown, the thick-film integrated LVDT signal conditioner also includes a fully sealed metal housing 13 and an Al2O3 ceramic substrate 14, which is sintered to the housing 13 using lead-tin-silver solder. Resistors R1-R4 and R13 are surface-mount resistors 10, the remaining resistors are thick-film resistors 2, and capacitors C1-C11 are surface-mount capacitors 11. The JEFT input dual operational amplifier 3, voltage reference chip 4, high-precision dual operational amplifier 5, and rail-to-rail dual operational amplifier 6 are bonded to the ceramic substrate using insulating adhesive. The bottom cathode of the diode 8 and the drain of the J-type field-effect transistor 9 are bonded to the corresponding gold conductive strips on the substrate using conductive adhesive. The surface-mount resistors 10, surface-mount capacitors 11, and power operational amplifier 7 are back-reflow soldered to the thick-film ceramic substrate 14. The leads of the surface-mount resistors 10 and surface-mount capacitors 11 use palladium-silver pads. Gold paste and resistor paste are printed on the ceramic substrate 14 to form gold conductive strips 1 and thick film resistors 2. The chips mentioned above are all bare chips, that is, unpackaged chips. 25μm inner lead gold wire 15 is used to connect the chip and the corresponding gold conductive strip, and 40μm outer lead gold wire 16 is used to connect the corresponding gold conductive strip and the tube shell pin 12.

[0018] This thick-film integrated LVDT signal conditioner uses rail-to-rail operational amplifier U2A, paired with thin-film resistors R1-R4 and capacitors C1 and C6, to control the oscillator frequency between 2.9kHz and 3.1kHz within a -55°C to 125°C temperature range, keeping the output voltage temperature drift below 50mV. High-precision operational amplifiers U4A and U4B reduce the demodulated signal output ripple to less than 5mV, and a high-precision voltage reference chip U1 ensures the final output voltage linearity variation is less than 0.1%.

[0019] The above are only specific embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A thick-film integrated LVDT signal conditioner, comprising a fully sealed metal housing and a ceramic substrate, wherein the ceramic substrate is a thick-film ceramic substrate sintered to the housing and provided with a gold conduction strip. Within the housing are disposed an excitation generation circuit, a demodulation circuit, and a voltage reference circuit, wherein the voltage reference circuit includes a reference voltage chip U1 and capacitors C8 and C9. The present invention is characterized by: The excitation generating circuit includes a rail-to-rail operational amplifier U2A, a power operational amplifier U5, resistors R1-R13, and capacitors C1-C6, wherein the rail-to-rail operational amplifier U2A, resistors R1-R4, capacitors C1 and C6 generate a triangular wave signal with a bias of 5V, which is filtered by a first low-pass filter composed of resistor R5 and capacitor C2, and then passes through resistor R6. One path is isolated by capacitor C3 and then input to the reverse input terminal of the power operational amplifier U5 through resistor R9; a voltage divider circuit composed of resistors R8, R11 and R12 superimposes a 5V bias signal on the reverse input terminal of the power operational amplifier U5; the other path passes through resistor R7 and then passes through a second low-pass filter composed of resistor R10 and capacitor C5 for filtering, and then is differentially amplified by the power operational amplifier U5 to convert it into a sinusoidal wave signal with a certain driving capability, and then the sinusoidal signal is isolated by capacitor C4 to finally provide an excitation signal to the primary side Y1 of the sensor, and the modulation signal is output by the two secondary sides F1 and F2 of the sensor coil; The demodulation circuit includes operational amplifiers U3A, U7A and U7B, high-precision operational amplifiers U4A and U4B, field-effect transistor T1, diodes D1 and D2, resistors R14-R31, capacitors C10-C11, and two sinusoidal wave signals of different sizes generated by the secondary sides F1 and F2 of the sensors. The signals are differentially amplified through resistors R14-R19 and the operational amplifier U3A; one path is input to the drain of the field-effect transistor T1 and the non-inverting input terminal of the operational amplifier U7B through resistor R21, and the square wave signal output by the operational amplifier U7A is input to the gate of the J-type field-effect transistor T1 through the DC blocking capacitor C7, the reverse diode D1, resistors R26 and R27. When the J-type field-effect transistor T1 is working normally, the waveform of the drain is the demodulated signal waveform, which is a half-wave signal of the sine wave. The other path is input to the operational amplifier through resistors R22 and R28. The inverting input terminal of the operational amplifier U7B, the resistor R23 is connected between the output terminal and the inverting input terminal of the operational amplifier U7B, the half-wave signal is amplified by the operational amplifier U7B, and then passed through the resistor R24, the low-pass second-order filter composed of the high-precision operational amplifier U4A, the resistor R25, and the capacitor C11 to filter the half-wave signal into a DC voltage signal, and then passed through the resistor R31, the reverse proportional amplifier composed of the high-precision operational amplifier U4B and the resistor R30 to amplify the demodulated DC voltage signal, the capacitor C10 is connected to the output terminal of the high-precision operational amplifier U4A and the junction of the resistors R24 and R25, the negative power supply input terminal of the operational amplifier U3A is connected to the system ground through the resistor R20, and the non-inverting input terminal of the high-precision operational amplifier U4A is connected to the system ground through the resistor R29, which is used to convert the change of the sensor position into the change of the output voltage.

2. A thick film integrated LVDT signal conditioner according to claim 1, characterized in that: The resistors R1 to R4 and R13 are surface-mount resistors, and the remaining resistors are thick-film resistors. The capacitors C1 to C11 are surface-mount capacitors. The operational amplifier U3A, the operational amplifier U7A, and the operational amplifier U7B respectively use JEFT input dual operational amplifiers. The JEFT input dual operational amplifier, the reference voltage chip U1, the high-precision dual operational amplifiers U4A and U4B, and the rail-to-rail dual operational amplifier U2A are bonded to the ceramic substrate with insulating glue. The bottom surfaces of the diodes D1 and D2 are negative electrodes and are bonded to the corresponding gold conduction strips with the drain of the J-type field-effect transistor T1 with conductive glue. The back of the power operational amplifier U5 is welded to the ceramic substrate. The chips and the corresponding gold conduction strips are connected by inner lead gold wires, and the corresponding gold conduction strips and the tube shell pins are connected by outer lead gold wires.

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