• A linear assembly moves in either direction, left or right, by
manually turning the scaled control
• One complete revolution of the scale moves the linear assembly
1 mm
• The devices available are– A linear scale– A variable area
capacitor– A reed switch– A linear variable differential
transformer– A linear potentiometer …
LVDTLinear variable differential transformer
Soft iron
Reed Switch
Experiments
• 1. Linear variable differential transformer (LVDT)• 2.
Variable area capacitance• 3. Reed switch• 4. Linear potentiometer•
5. Four-bit optical encoder
Investigate the variable properties of LVDT
Investigate the differential properties of LVDT
Experimental Results
Linear measurement with LVDT
Phase-Sensitive Detection
• Require a frequency reference• Typically an experiment is
excited at a fixed frequency
and the lock-in detects the response from the experiment at the
reference frequency
Phase-Sensitive Detection
• Amplify the signal and then multiply it by the lock-in
reference using a phase-sensitive detector or multiplier
• The output of the PSD is two AC signals
Phase-Sensitive Detection
• If the output is passed through a low pass filter, the AC
signals are removed
• If wr equals wL, the difference frequency component will be a
DC signal and the filtered output will be
Experimental Results
Variable capacitor with or without gain
Experimental Results
Reed switch
Experimental Results
Linear potentiometer
Experimental Results
Four-bit optical encoder (D/A conversion)
Experimental Results
Experimental Results
實驗原理
– LVDT + Reed Switch相關問題
– 請比較 LVDT、Variable area capacitance 和Linear
potentiometer的實驗結果，並說明這三種方式各自的優缺點。(準確度、靈敏度、線性度、適用範圍、、、)
–請分析LVDT實驗誤差的來源與大小。
Yu-Chuan SuRectangle
Yu-Chuan SuSticky NoteMigrationConfirmed set by Yu-Chuan Su
