| 摘要 |
<p>1480193 Measuring moisture SAINTGOBAIN INDUSTRIES 16 April 1975 [19 April 1974] 15688/75 Heading G1N [Also in Divisions H2 and H5] A window pane 1 for a motor vehicle is provided on its internal face with a network 2 of electrically resistive strips printed on to the pane, and with a humidity detector Ha having two terminals one of which is connected to the network. Preferably the detector has a pair of inter-digitated electrodes of which one connects to a tab 2a formed on the uppermost resistance strip of the network. The detector forms with a resistance 23 a voltage divider for the signal generated by a multivibrator 11. The presence of moisture on the pane reduces the voltage supplied to the diode 15 whereby transistor 17 is blocked. Thus transistor 18 is enabled to act via the relay S to supply current to the network for heating the pane. In an alternative embodiment Fig. 2 (not shown) two humidity detectors are provided (Ha, Hb) coupled to the control circuit through respective capacitors (21a, b). The heater element may be energized in response to a bi-metallic strip (T) when the passenger compartment temperature is so low that there is a risk either of frost on the detector or of ice on the external face of the pane.</p> |
