Author: Michael O. Paiva,
Microchip Technology, Inc.
RATIOMETRIC MEASUREMENT (ANALOG DIVISION)
One of the most difficult circuits to build is one which will divide one analog signal by another. Two voltage-to-frequency (V/F) converters
can do such division with ease. The numerator is counted directly as a signal, while the denominator forms the time base.
Output = N
FIGURE 1: Ratiometric measurement (analog division).
Flow rates and revolutions per second are nothing more than frequency signals, since they measure the number of events per time
period. Optical and magnetic sensors will convert these flows and revolutions into a digital signal which, in turn, can be converted to a
proportional voltage by the use of a frequency-to-voltage (F/V) converter. A simple voltmeter will then give a visual indication of the
(Optical or Magnetic)
FIGURE 2: RPM/speed indicator.
© 2002 Microchip Technology, Inc.