Study of automatic measurement system of displacements using LVDT

Abstract

In Taiwan bridges are common transport infrastructures and there are many elevated bridges in the major cities Generally elevated structures may be affected by self-weight seismic forces wind and driving vehicles and these factors can cause vibrations of the bridge Moreover the safety of structures is related to the vibration displacement which cannot be underestimated Thus an effective automatic monitoring system of displacements is important The use of own developed measurement system can save the cost of commercial software and does not need to buy the full sets of devices from original equipment manufacturer Furthermore the measuring program can customize the functions to satisfy the use of demands The linear variable differential transformer (LVDT) is a widely used displacement sensor which has the advantage of high sensitivity and good linearity The general signal amplifier on the market can be used for LVDT which can meet the power supply requirement and return the measured voltage but it has a high cost and cannot systematically use the LVDT for measurement The LVM-110 voltage module can basically meet the power supply requirement and get the voltage output signal which can be used to replace the signal amplifier The LVM-110 voltage module is low-cost stable output signal and low power supply requirement In conjunction with the measuring program "aa exe" having the automatic archiving function data acquisition card (NI USB-6218) self-made power supply equipment and LVDT the automatic measurement system of displacements can be established Next the sensitivity of the LVDT can be obtained from the laboratory testing experiment and the results also showed that the LVDT has good linearity Finally to verify the accuracy of the measurement system the INSTRON-8800 was used in the dynamic displacement validation experiment The average errors of the measurement system are within the range of 1% to 3% which is acceptably accurate

Date of Award	2014 Aug 15
Original language	English
Supervisor	Shen-Haw Ju (Supervisor)