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Smiths Industries of London points out that the wires passing into aircraft
fuel tanks to feed the fuel gauges can provide a conducting path for lightning
strikes, increasing the risk of explosions (GB 2 340 603). Its new sensor
supplies power to the fuel probe using piezoelectric transducers clamped to
either side of the fuel tank. The outer one is fed a high-frequency electrical
signal which makes it vibrate. This causes the inner one to vibrate, generating
a high-frequency current that powers the probe. Because the transducers couple
only at the high frequency, they block the DC voltage from a lightning strike.