AN INTEGRATED CIRCUIT FREQUENCY METER

Impulse frequency meters available at present measure the interval between successive pulses and use a successive approximation technique to build up the hyperbolic transfer function needed to obtain the reciprocal of time. In this paper is presented a method for impulse frequency measurements with four operational amplifier units. Use is made of the mathematical relationship d/dx (loge x)=1/x., The four functional stages of the instrument are thus an integrator, a logarithmic amplifier, a level restorer, and a differentiator. Measurements over 2·5 decades are possible without necessitating any switching of ranges. By switching in different values of capacitors for integration and differentiation, accurate frequency measurements over any desired range may be selected. © 1969 International Federation for Medical and Biological Engineering.