MTS Series 311 Load Frame - Manual (Page 18)

Series 311 Load Frame 18
Functional Description
Introduction
Transducers
The load frame usually includes a force transducer and an LVDT (or other
displacement measurement device.
Force
The force transducer (also called load cell or force sensor) measures the amount
of tension or compression and rotational torque applied to it. It has four strain
gages that form a balanced Wheatstone bridge. When forces are applied to the
bridge, it becomes unbalanced and produces an electrical signal that is
proportional to the force applied to it. The force transducer is a resistive device
and requires a DC conditioner to process the axial signal from the Wheatstone
bridge.
LVDT
The LVDT measures the linear actuator’s travel. The LVDT consists of a
transformer with one primary and two secondary coils wound on a common
cylinder. The coil is stationary inside the actuator. A core is attached to the piston
rod of the actuator. As it moves inside the coil, it produces an electrical signal
that represents the position of the piston rod. The phase of the signal indicates the
direction the actuator rod is moving. An LVDT requires an AC conditioner to
process the signal.