analogue frequency meter

A true `universal meter` should be able to read not only voltage, current and resistance - but also other quantities. The usual multimeter will only do this when used as a `mainframe` in conjunction with `plug-ins`, that convert the input quantity into a form suitable for feeding into the actual meter. This article describes a `frequency plug-in` that will enable any multimeter (or voltmeter) to read frequencies between 10 Hz and 10 kHz.