Fundamentals of Measurement Technology Prof Wang Boxiong
Fundamentals of Measurement Technology (9) Prof. Wang Boxiong
4.6 Inductive transducers Inductive transducers are based on the voltage output of an inductor (or coil) whose inductance changes in response to changes in the measurand a classification of inductive transducers 1. Variable self-inductance a. Single coil(simple variable permeance) b. Two coil (or single coil with center tap) connected for inductance ratio 2. Variable mutual inductance a. simple two coi b. Three coil (using series opposition) 3. Variable reluctance a. Moving iron b. Moving coil C. Moving magnet
• Inductive transducers are based on the voltage output of an inductor (or coil) whose inductance changes in response to changes in the measurand. • A classification of inductive transducers : 1. Variable self-inductance a. Single coil (simple variable permeance) b. Two coil (or single coil with center tap) connected for inductance ratio 2. Variable mutual inductance a. Simple two coil b. Three coil (using series opposition) 3. Variable reluctance a. Moving iron b. Moving coil c. Moving magnet 4.6 Inductive transducers
4.6. 1 Self-inductance arrangements 1. Simple permeance-varying A simple permeance -varying transducer is composed of an iron core. a coil and an armature an air ga is arranged between the core and the armature when a current i flows through the coil, a magnetic flux m is generated within it, whose magnitude is proportional to the current z Won=li (4.22) where number fo turns self inductance
1. Simple permeance-varying 4.6.1 Self-inductance arrangements A simple permeance-varying transducer is composed of an iron core, a coil and an armature. An air gap is arranged between the core and the armature. When a current i flows through the coil, a magnetic flux m is generated within it, whose magnitude is proportional to the current i : W Li m = （4.22） where W = number fo turns L = self inductance (H )
4.6.1 Self-inductance arrangements I-coil 2-core armature b Fig. 4.15 Principle of permeance-varying transducer
4.6.1 Self-inductance arrangements Fig. 4.15 Principle of permeance-varying transducer 1－coil 2－core 3－armature
4.6.1 Self-inductance arrangements Also according to ohms law of magnetic circuit Wi (423) R where Wi=magnetic motive force R m reluctance H Substituting eq (4.23)into Eq (4.22) yields W L (424) R
Also according to Ohm’s law of magnetic circuit m m R W i = （4.23） where Wi = magnetic motive force (A ) Rm = reluctance ( −1 H ) Substituting Eq. (4.23) into Eq. (4.22) yields Rm W L 2 = （4.24） 4.6.1 Self-inductance arrangements