I use a DC circuit for my senior project to amplify a output signal from a temperature sensor (LM34DZ) so that the output from the sensor's would be large enough for a microcontroller (68HC12) to read. Bascially I use a scaler circuit to scale the temperature sensor output from the range of 0-1000mV to 0 to 5V. I'm not in the field yet, but hope to be very very soon.