Sampling frequency meter

The author describes a low-cost battery-powered instrument based on the c-mos Motorola MC146805 E2P microprocessor. In this instrument the input is sampled repetitively and compared with a table of values stored in memory, so that over time, a distribution of the sampled input is built up in 21 internal memory channels (20 channels plus 1 'over-range' channel). The program controlling the microprocessor can be adapted to suit different needs by simply changing the values stored in this table, and/or by changing the measuring period