Apparatus for monitoring the flow of a fluid medium

Claim 1

APPARATUS FOR MONITORING FLOW OF A FLUID MEDIUM ALONG A CONFINED PATH COMPRISING, IN COMBINATION, A COLD SEMICONDUCTOR RESISTANCE POSITIONED IN HEAT TRANSFER RELATION WITH THE FLOWING FLUID MEDIUM; SAID COLD SEMI-CONDUCTOR RESISTANCE HAVING, IN A LOW TEMPERATURE RANGE, A TEMPERATURE COEFFICIENT WHICH IS SUBSTANTIALLY EQUAL TO ZERO, SO THAT SAID RESISTANCE HAS SUBSTANTIALLY NO SIGNIFICANT CHANGE IN ITS OHMIC VALUE IN SAID LOW TEMPERATURE RANGE, AND HAVING, IN AN IMMEDIATELY SUCCEEDING HIGHER TEMPERATURE RANGE, A HIGH POSITIVE TEMPERATURE COEFFICIENT, SO THAT SAID RESISTANCE HAS AN EXTREMELY HIGH POSITIVE CHANGE IN ITS OHMIC VALUE IN SAID HIGHER TEMPERATURE RANGE; MEANS APPLYING A SUBSTANTIALLY CONSTANT POTENTIAL ACROSS SAID COLD SEMI-CONDUCTOR RESISTANCE TO EFFECT A HEATING CURRENT FLOW THERETHROUGH; THE HEAT CONTENT OF SAID COLD SEMI-CONDUCTOR RESISTANCE BEING DISSIPATED BY THE FLOWING FLUID MEDIUM IN ACCORDANCE WITH THE RATE OF FLOW THEREOF, WHEREBY THE OHMIC RESISTANCE VALUE OF SAID COLD SEMI-CONDUCTOR RESISTANCE IS RESPONSIVE TO THE RATE OF FLOW OF THE FLUID MEDIUM; SAID LOW TEMPERATURE RANGE CORRESPONDING TO A RATE OF FLOW OF THE FLUID MEDIUM ABOVE A PREDETERMINED VALUE AND SAID SUCCEEDING HIGHER TEMPERATURE RANGE CORRESPONDING TO A RATE OF FLOW OF THE FLUID MEDIUM BELOW SAID PREDETERMINED VALUE; AND CURRENT FLOW RESPONSIVE INDICATOR MEANS IN ELECTRIC CIRCUIT CONNECTION WITH SAID CONSTANT POTENTIAL COLD SEMI-CONDUCTOR RESISTANCE TO PROVIDE AN EFFECTIVE AMPLITUDE INDICATION WHEN THE RATE OF FLOW OF THE FLUID MEDIUM IS BELOW SAID PREDETERMINED VALUE.