Magtrol TM 301, Руководство пользователя

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3. OPERATING PRINCIPLES
The TM Series In-Line Torque Transducer can be defined as an inductive transducer operating on the basis
of a differential voltage transformer having a variable coupling factor.
3.1 TORQUE TRANSDUCER ARCHITECTURE
The part of the transducer effectively measuring the torque is composed of three elements: a shaft with a
deformation zone, a pair of coils and two metallic cylinders.
Fig.3-1 TM Torque Transducer Principal Elements
The primary and secondary coil composing the differential transformer are separated by two concentric
aluminum cylinders. These cylinders are connected to the torque measuring shaft—the external cylinder
on one side of the deformation zone and the internal cylinder on the opposite side. Both cylinders have
two series of slots on their surface. When there is no torque being applied to the measuring shaft, the slots
in both cylinders fail to overlap. Because the cylinders are non-magnetic, there is total screening and dif-
ferential induction cannot be generated between the primary and secondary coil.
As torque is applied to the shaft, the deformation zone undergoes increasing angular deformation. As
torque is sensed, the overlap between the slots increases creating an opening for the induction flux. The
amount of differential induction is proportional to the applied torque. In this way, when the primary coil is
excited by a sinusoidal voltage, the secondary coil produces a voltage whose magnitude is dependent on
the applied torque.
3.1.1 DIFFERENTIAL TRANSFORMER
The primary coil of the transformer consists of two equal windings mounted in series. It is excited by an
alternative current having a frequency of 20 kHz which is generated by the transducer’s built-in electronics.
In addition, a constant current is supplied to the primary coil in order to determine the temperature of the
entire measuring unit and to compensate the temperature signal.
The secondary coil consists of two windings in phase opposition. This determines the spacing between the
cylinder slots and produces a torque-proportional dynamic voltage signal.
Internal cylinder External cylinder Primary coil
Deformation zone Slots Secondary coil
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TM
series
OPERATING PRINCIPLES