Integrated linear variable differential transformer (LVDT) displacement sensor for measuring micro strain of pile foundation

Abstract

The invention discloses an integrated linear variable differential transformer (LVDT) displacement sensor for measuring micro strain of a pile foundation. The integrated LVDT displacement sensor comprises a fixed amplitude oscillator, a LVDT displacement sensor, a signal amplifier and a single chip microcomputer, wherein the excitation signal input end of the LVDT displacement sensor is connected with the output end of the fixed amplitude oscillator; the detection signal output end of the LVDT displacement sensor is connected with the input end of the signal amplifier; and the acquisition voltage signal input end of the single chip microcomputer is connected with the output end of the signal amplifier. The LVDT displacement sensor has extremely high common-mode rejection capability, for instance, temperature change parameters are converted into common modulus in output response of the displacement sensor, so that the integrated LVDT displacement sensor has high rejection capability for the common modulus such as temperature change, cannot be influenced by temperature drift almost, can directly output displacement without secondary transformation calculation and has extremely fine measurement resolution and linearity.

Description

technical field [0001] The present invention relates to a displacement sensor circuit, in particular to an integrated LVDT (Linear Variable Differential Transformer, abbreviated as LVDT) displacement sensor for measuring micro-strain of pile foundation. Background technique [0002] The traditional method of measuring the micro-strain of pile foundation in the field of construction is realized by using a kind of stress sensor called steel string. The principle is: when an exciting electric pulse is applied to a steel string whose two ends are tightened, the steel string will generate exciting vibration; assuming that the steel string is fixed in a cavity of a rigid body, when the rigid body is subjected to an external force When the steel string is excited by the electric pulse, the steel string will vibrate, and its oscillation frequency will also change accordingly. By comparing the current measurement frequency with the previous measurement frequency, the strain value is...

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Problems solved by technology

[0004] (1) Since the two ends of the steel string are tight and are always under tension, the steel string will undergo natural deformation, resulting in a change in its output natural frequency;

[0005] (2) The consistency of the output signal of the steel string stress gauge is poor, and its output response is related to the tightness of the steel string and the consistency of the steel string material, so each sensor needs to be calibrated independently;

[0007] (4) When measuring the strain of the pile foundation, the steel bar to be tested needs to be cut off, and the steel string sensor is welded between the two fractures of the steel bar. Therefore, when the pile foundation is loaded, if the elastic modulus of the steel string sensor is the same as the measured If the steel bars are inconsistent, the measured value has no meaning to guide the construction;

[0008] (5) The measured value needs to be converted twice through empirical parameters, the accuracy is poor, and it is not comparable and consistent

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