Measuring apparatus having a sensor located remotely from its electricity power supply
First Claim
1. Apparatus for measuring a physical characteristic comprising a sensor having a first electrical characteristic which is directly modifiable by and representative of the physical characteristic to be measured, an electrical link comprising two conductors connecting said sensor to a remote electrical power supply and a third conductor connecting the sensor with means for measuring the electrical characteristic which is representative of the measured physical characteristic, the link having a second electrical characteristic capable of disturbing the measurement made by the sensor, wherein the apparatus further comprises secondary measuring means located proximate the power supply responsive at any given moment to a measured value of the second electrical characteristic of the link plus sensor assembly for controlling the power supply as a function of said measured value in order to eliminate the disturbance that would otherwise result therefrom.
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Accused Products
Abstract
The measuring apparatus comprises a sensor (11) having a first electrical characteristic (balance of inductance) which is directly modifiable by the magnitude of a quantity or characteristic to be measured (e.g. pressure). A remote electrical power supply (27) excites the sensor over first and second conductors (28, 29) of an electrical link (22) having a second electrical characteristic (e.g. resistance) which is capable of disturbing the measurement. A third conductor (21) in the link is connected to a measuring instrument (24).
In order to avoid measurement errors due to leakage currents in the link, the power supply (27) continuously monitors the electrical characteristics of the link and regulates its excitation output as function thereof and in such a manner as to tend to eliminate disturbing effects on the measurement.
19 Citations
7 Claims
- 1. Apparatus for measuring a physical characteristic comprising a sensor having a first electrical characteristic which is directly modifiable by and representative of the physical characteristic to be measured, an electrical link comprising two conductors connecting said sensor to a remote electrical power supply and a third conductor connecting the sensor with means for measuring the electrical characteristic which is representative of the measured physical characteristic, the link having a second electrical characteristic capable of disturbing the measurement made by the sensor, wherein the apparatus further comprises secondary measuring means located proximate the power supply responsive at any given moment to a measured value of the second electrical characteristic of the link plus sensor assembly for controlling the power supply as a function of said measured value in order to eliminate the disturbance that would otherwise result therefrom.
Specification