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1. Introduction to the Temposonics II Linear Displacement Transducer (LDT)
The Temposonics II LDT precisely senses the position of an external magnet to measure displacement with a high
degree of accuracy and resolution. Using the principle of magnetostriction (see Section 1.1, below), the
Temposonics II LDT measures the time interval between the initiation of an interrogation pulse and the detection
of a return pulse. A variety of interface devices use the data derived from these two pulses and generates an ana-
log or digital output to represent position.
1.1 Theory of Operation/Magnetostriction
The interrogation pulse travels the length of the transducer by a conducting wire threaded through a hol-
low waveguide. The waveguide is spring loaded within the transducer rod and exhibits the physical prop-
erty of magnetostriction. When the magnetic field of the interrogation pulse interacts with the stationary
magnetic field of the external magnet, a torsional strain pulse or “twist” is produced in the waveguide.
This strain pulse travels in both directions, away from the magnet. At the end of the rod, the strain pulse
is damped within the “dead zone” (2.5 inches in length). At the head of the transducer, two magnetically
coupled sensing coils are attached to strain sensitive tapes. The tapes translate the strain pulse through
coils to an electrical “return pulse”. The coil voltage is then amplified in the head electronics before it is
sent to various measuring devices as the conditioned “return pulse”.
Figure 1-1
Waveguide Interaction
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