Digitized displacement transducer
AssigneeNorthrop Corporation
InventorLeo Spiegel
Life of this patent
Estimating the term…
Abstract
A displacement measuring transducer performs a direct conversion of changes in physical position, particularly angular position, into a digital form suitable for input to a digital microprocessor. The transducer is of the inductive type. Two inductance legs are connected at a common input to form a three-terminal bridge device. To sense positional changes, a step voltage is applied to the input and the transient response at the output of each leg is sampled periodically. Digital circuitry compares the responses of each leg to a fixed reference voltage and produces a binary digital count proportional to the motion sensed by the transducer. This transducer provides high resolution and low noise over a wide dynamic range. It also allows temperature compensation and scale factor calibration.
Claims11
Means for converting a displacement directly into a digital signal that accurately represents the magnitude of the displacement comprising,
- a differential inductive transducer having first and seconds legs that each include inductive and resistive elements, said legs being arranged in a bridge configuration with a common input and separate outputs, and said inductive elements of each of said legs having a variable inductance,
- means for producing and applying an electrical excitation signal to said common input, said signal being a train of step-voltage pulses of substantially constant maximum amplitude and pulse interval, said excitation signal producing first and second transient signals at said outputs of said first and second legs, respectively,
- means for producing a constant reference voltage associated with said excitation signal,
- means for producing a timing signal associated with each of said legs that is derived from a comparison of said transient output signal to the reference voltage, said transient signal having a duration that corresponds to the time constant of the leg and is a direct measure of the instantaneous displacement of said leg, and
- means for converting said timing signals into a digital count.
The method of operating a differential inductive electro-mechanical transducer of the type comprising two motion-sensing variable inductances that directly convert changes in the physical position of a body into a high-accuracy digital representation of the magnitude and direction of said displacement, said method comprising the steps of:
- forming an input terminal of said transducer by connecting the two said inductances at a common point,
- forming a pair of output terminals of said transducer by connecting a resistor in series with each said inductance,
- exciting the three-terminal transducer so formed at its input terminal by a step voltage,
- providing a reference voltage,
- comparing the transient response at each said output terminal to said input step voltage against said reference voltage,
- emitting a first and second comparison signal when each said transient response equals said reference voltage, the difference in time between said signals being proportional to said physical displacement, and
- converting the difference in said comparison signals into said high-accuracy digital representation of the displacement of said body.
Dependencies are inferred from the claim text.