Inductive displacement sensor apparatus
AssigneeRobert Bosch GmbH
InventorErich Zabler
Life of this patent
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Abstract
A variable inductor having a U-shaped magnetic core with a short-circuiting plate providing a short-circuiting ring for both legs of the core movable along the core legs in response to a displacement to be measured is connected in an electronic circuit to generate oscillation of a frequency that is either directly or inversely proportional to the displacement. For the inversely proportional case, the variable inductance component can be combined with an integrator function and connected to an operational amplifier, for generation of the output frequency with a small number of electrical components. Additional circuit means may be used to improve linearity at higher output frequencies, or to provide arbitrary non-linear displacement-frequency characteristics.
Claims10
Inductive displacement sensor apparatus comprising:
- a variable inductor having a substantially U-shaped core (11) of ferromagnetic material, an electromagnet winding (10) thereon and a short-circuiting ring member (12) arranged to provide a short-circuit path around and adjacent to each leg of the core at a position which is movable along the length of the core legs in accordance with a displacement to be measured, and
- an oscillator circuit (30,32,34) connected to said electromagnet winding in such a way that said electromagnet winding forms at least part of the frequency determining portion of said circuit, whereby the frequency of said oscillator is dependent upon the position of said short-circuiting ring member (12), said oscillator circuit including, in sequential connection, a comparator (30) having a hysteresis characteristic, said winding of said variable inductor (32) and an integrator (34), and the output of said integrator (34) being connected to the input of said comparator (30).
Inductive displacement sensor apparatus comprising:
- a variable inductor having a substantially U-shaped core (11) of ferromagnetic material, an electromagnet winding (10) thereon and a short-circuiting ring member (12) arranged to provide a short-circuit path around and adjacent to each leg of the core at a position which is movable along the length of the core legs in accordance with a displacement to be measured, and
- an oscillator circuit (30,32,34) connected to said electromagnet winding in such a way that said electromagnet winding forms at least part of the frequency determining portion of said circuit, whereby the frequency of said oscillator is dependent upon the position of said short-circuiting ring member (12), said oscillator circuit including an LR integrator circuit (60-62;
- 62,90) including said variable inductor for providing variable inductance (62,10-12) and a switching comparator circuit (30) having a hysteresis characteristic, having its input and output respectively connected to the output and input of said LR integrator, and connected in circuit for switching in alternation between oppositely poled voltages which are thereby provided in alternation at the output of said comparator circuit (30).
Dependencies are inferred from the claim text.