The Models 441A and 441AL produce an analog output that precisely represents the frequency of an applied input signal. Adjustable “input frequency to output voltage” set points allow the user to closely bracket the frequency of interest. A unique crystal-controlled micro-controller design provides fast response, high conversion accuracy, and low output noise that is independent of frequency. The front-panel display shows the input frequency with up to five-digit resolution. All operating parameters are set using the display and one other front-panel control. The input signal conditioner automatically provides stable operation for a wide range of pulse-, square-, and sine-wave signals, or logic-level signals, up to 100 V in amplitude. Three selections each of input sensitivity and input bandwidth, plus a unique digital periodic filter that cancels unwanted output variation caused by an input signal whose frequency varies in a periodic manner, are provided.