The CA1524 pulse-width modulator integrated circuit presently in use in voltage-regulator applications can also be employed as the driving source for an electronic scale. As shown in the block and schematic diagrams of Figures 1 and 2, half of the output of the CA1524, Q2, is used in a lowvoltage (2.2 volts) switching regulator that drives the LEDs displaying the weight measured. The remaining output stage, Q1, is used as a driver for the sampling plates PL1 and PL2. Since the CA1524 contains a 5V internal regulator and is able to operate over a wide voltage range, 8V to 40V,a single 9V battery is sufficient to power the total system.The two sampling plates, PL1 and PL2, are driven by
oppositely phased signals (the frequency is held constant but the duty cycle may change) from the pulse-width modulator integrated circuit CA1524. The sensor, S, located between the two plates forms with them an effective divider
network of the capacitance bridge type.