Magnetic coupling for a flowmeter

Claim 1

IN APPARATUS FOR INDICATING THE POSITION OF AN ELEMENT WHICH IS DISPLACEABLE ALONG A RECTILINEAR PATH OF ASCERTAINED LENGTH M, IN COMBINATION, A FIRST ELONGATED AND END-POLARIZED MAGNET OF LENGTH EQUAL TO AT LEAST ABOUT 0.3M, CARRIED BY SAID ELEMENT FOR AXIALLY DIRECTED RECTILINEAR MOVEMENT THEREWITH ALONG A MAGNET PATH HAVING SAID LENGTH M; AND A SECOND ELONGATED AND ENDPOLARIZED MAGNET HAVING A LENGTH BETWEEN POLES EQUAL TO BETWEEN ABOUT 0.15 AND ABOUT 0.67 TIMES THE LENGTH BETWEEN POLES OF SAID FIRST MAGNET, MOUNTED FOR ANGULAR DISPLACEMENT ABOUT AN AXIS OF ROTATION EXTENDING THROUGH ITS MIDPOINT AND PERPENDICULAR TO ITS MAGNETIC AXIS SO THAT ITS PLANE OF ROTATION CONTAINS ITS MAGNETIC AXIS, AND DISPOSED ADJACENT SAID MAGNET PATH IN SPACED RELATION THERETO, WITH SAID AXIS OF ROTATION LYING IN A PLANE PERPENDICULARLY BISECTING SAID MAGNET PATH AND SAID PLANE OF ROTATION ORIENTED AT AN ANGLE OF NOT MORE THAN ABOUT 60* TO THE LINE PERPENDICULAR TO THE AXIS OF SAID MAGNET PATH DRAWN FROM SAID SECOND-MAGNET MIDPOINT, SUCH THAT SAID SECOND MAGNET IS MAGNETICALLY COUPLED TO SAID FIRST MAGNET TO UNDERGO ANGULAR DISPLACEMENT AS AFORESAID RESPONSIVE TO AND IN SUBSTANTIALLY LINEAR PROPORTION TO DISPLACEMENT OF SAID FIRST MAGNET ALONG SAID MAGNET PATH.