Capacitive_transducer_signal_conditioner

Published:2009/7/24 4:05:00 Author:Jessie | From:SeekIC

Fig. 14-19 This circuit uses an LM2907 to condition the output of a capacitive transducer, and to mix this output with another variable. If the other signal is fixed at 60-Hz, as shown, then the output is proportional to the capacitive-transducer output only. If the other signal is variable, the transducer acts as a multiplier. For example, in flow-measurement indicators, the input frequency can be a variable that depends on flow rate, such as a signal generated from a paddle wheel, propeller, etc. The capacitive-transducer can be an indication of orifice size or aperture size (such as a throttle). The product of these two indicates volume flow, where the output voltage is proportional to size times rate. A thermistor can be added to R1 to convert the volume flow to mass flow. A combination of these signal-conditioned inputs, including control voltage on the supply, can be used to provide complex analog functions, where several variable or fixed factors must be multiplied. National Semiconductor Linear Applications Handbook, 1991. p. 432.



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