| 摘要 |
<p>1. Thermal pick-up for a fluid flow in a conduit, comprising a sensitive element of the thermistor type disposed in the fluid current, at least one electrical power supply for the sensitive element, an electronic circuit with a feedback loop modifying in one direction the voltage applied to the sensitive element when that voltage exceeds a first threshold value, modifying the said voltage in the opposite direction when that voltage falls below a second threshold value, and producing at its output a rectangular signal characteristic of the fluid flow and one of the levels of which corresponds to the heating time of the sensitive element and the opposite level to its cooling time, characterized in that it comprises at least one circuit (24, 25, 26) for squaring the rectangular signal (A), including at the input a first low-pass filter (24), a comparator-amplifier (26), the period of comparison of which is controlled by a signal (~A) complementary to that applied to the first low-pass filter and a second low-pass filter (25) at the output of the comparator-amplifier (26) delivering a voltage proportional to the square of the cyclic ratio (t/T) of the rectangular signal (A).</p> |
