Design consideration and performance of a digital lock-in amplifier with 68HC11 microcontroller

Abstract

The lock-rn amplifier technique is frequently used in characterization of optoelectronic devices. A digital lock-in amplifier and a digital direct synthesis signal generator are implemented with a general propose 68HC1 1E1FN microcontroller. The resolution in frequency is less than 1 Hz. The digital lock-in amplifier operates over a frequency range from 1 Hz to 1 kHz and can measure signal at any harmonic of the reference signal. Typical error is less than 0.5%for the range of frequencies reported. This thgital lock-in technique is inexpensive and can be used in experiments with low frequency response.