This ckt measures audio frequency signals. Input between 2.5 and 5 V. R10k can be set as low as 2.2k and C200 microF can be set as low as 10 microF, together these determine the range. Ammeter represents needle meter. Meter should be within 0-1 ma. Use 10k pot to calibrate meter.
Omit input capacitor and hook up a suitable pulse generator directly to pin 2 for testing. Okay to add amplifier for small signal input. Replace input cap for regular audio signal measurement.
