| 摘要 |
A circuit for sensing the electrical conductivity of fluid comprising a pair of electrodes adapted to be exposed to the fluid, a voltage source connected to one of the electrodes, a load connected to the other of the electrodes, a firing circuit branch including a firing capacitor connected to the other electrode, a conductivity sensing circuit branch including a sensing circuit capacitor connected to the other electrode and to the voltage source, and characterized by a switch connected in controlled relation to the sensing circuit branch and in controlling relation to the firing circuit. In response to the electrodes being exposed to fluid having a predetermined condition of electrical conductivity, current flows in the sensing circuit branch which operates the switch to connect the firing circuit in a manner preparing it for firing, i.e. charging the capacitor therein. After a predetermined time, i.e. after the firing capacitor is charged, the switch operates to connect the firing circuit to the load for operating the same. The sensing capacitor is selected to charge significantly more rapidly than the firing capacitor. A current regulator is connected between the voltage source and load. The switch can be a relay with the control coil thereof in the sensing circuit branch. The load can be an electro explosive device in a release mechanism for uncoupling a parachute canopy from its load upon landing in water.
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