4.3 Servomechanics (3)

Question 1

what does LVDT stand for?

Answer 1

linear variable differential transmitter

Question 2

what does a LVDT do?

Answer 2

convert rectilinear motion of an object into corresponding electrical signals

Question 3

where might LVDT be used?

Answer 3

rudder

Question 4

what is the construction of a LVDT?

Answer 4

primary coil, 2 secondary coils wound in opposite directions and connected in series and an iron core

Question 5

how does a LVDT operate?

Answer 5

the coupling between primary and secondary coils change according to the position of iron core,

so that amplitude and phase position of the output voltage depends on the relative position of the iron core

Question 6

in inductance transmitters, how does the ac current method work?

Answer 6

target placed close to an inductor increases inductive reactance, increasing resistance to current flow.

target moved away, inductive reactance is reduced and current can flow.

Proximity switch

Question 7

in inductance transmitters, how does the induced voltage method work?

Answer 7

no voltage is induced with a magnet and a coil as there is no relative movement.

when a conductive target is brought into proximity, magnetic field will increase in flux and voltage induced in coil.

frequency is the same as the movement of the target

Question 8

where might induced voltage inductance transmitters be used?

Answer 8

to measure engine shaft rpm

Question 9

how may a capacitance transmitter work?

Answer 9

the space between the plates is calculated using the dielectric.

ie fuel/air. air is dielectric, less air, more fuel, more air, less fuel