| 摘要 |
<p>A flow switch or flow measuring apparatus (10) including a measuring probe adapted to extend into the flow path of a fluid, said measuring probe (15) including two spaced-apart measuring electrodes (21, 22); a power supply having a pair of terminals, one of said terminals being connected to one of said measuring electrodes and the other of said terminals being connected to the other of said measuring electrodes; a resistive load (25) electrically interposed between said other measuring electrode and said other terminal; a sensing device connected to said other measuring electrode for sensing an electrical potential drop or measuring the electrical potential drop between said measuring electrodes across the fluid; comparison means (16) electrically associated with said sensing device, said comparison means (16) being adapted to compare the measured or sensed electrical potential drop with a predetermined electrical potential drop for the fluid at a predetermined flow. Preferably, the comparison means includes a second probe (16) having two spaced-apart reference electrodes (23, 24), the second probe (16) being adapted to extend into a region of relative quiescence in the fluid remote from the measuring probe (15), one reference electrode being electrically connected to the other terminal, the other reference electrode being electrically connected to the other measuring electrode, and a second resistive load (26) being electrically interposed between the measuring electrodes (21, 22), the sensing device being electrically connected to the other reference electrode. It is also preferred that the resistive loads (25, 26) are of equal value and that the polarity of the electrodes is reversed on a regular basis.</p> |
