f-to -v converter for multimeter

Most frequency measurements are carried out by means of a digital frequency meter or else on an oscilloscope. However both these instruments are relatively expensive, and thus not often `standard equip-ment` for the hobbyist. One way to measure the frequency of a signal without investing in specialised equipment is to use a frequency-voltage converter, which can then be `plugged in` to an ordinary multi-meter. That is the function of the circuit described here. A meter with a 5 V range should be used; the conversion ratio is linear, assuming the scale is calibrated in ms ( 1 V = 5 ms).