Stroke: LVDT

Commercial LVDTs have a full range stroke from 0.1 to 80 mm with a sensitivity of about 25 to 1250 V/m depending upon the frequency of excitation and size of stroke. 

LVDTs are extremely reliable. As a rule, failures are limited to rare electrical faults which cause erratic or erroneous indications. An open primary winding will cause the indication to fail to some predetermined value equal to zero differential voltage. This normally corresponds to mid-stroke of the valve. A failure of either secondary winding will cause the output to indicate either full open or full closed. 

Potentiometer and LVDT position indicators provide accurate indication of valve and rod position throughout their travel. In some applications, LVDTs can be used to indicate open and closed positions when small secondary windings are used at either end of the valve stem stroke. 

Linear position Linear motion is typically driven by the use of lead screws, ball screws, or worm drives with ranges from less than a 25 mm to over 6 m. Linear sensors for position feedback in the lower range include LVDTs, magnetic, and optical encoders. For longer strokes, the linear feedback devices include encoders and magnetostrictive position transducers. Optical encoders are practical up to 2 m. Magnetostrictive position transducers can be used up to 20 m. 

Institution Maximum load (kN) Maximum compression rate (mm/s) Displacement LVDT stroke range (mm) Upper Lower Controlling computer Manufacturer... 

During the tests the actuator displacements and the displacements in correspondence of the horizontal stiffeners ofthe panels have been measured through 8 LVDTs with a stroke of 10 mm and accuracy <0.10% (Figure 15). A100 kN load cell measures the load applied at any time. It was thus possible to determine the force-displacement plots described in the following section. 

---