A noninvasive photoplethysmographic sensor system for mobile animals such as small rodents, namely rats and mice is useful such as in a laboratory research environment. The noninvasive photoplethysmographic sensor for mobile animals such as small rodents utilizes multiple FFTs in the processing of the phtotoplethysmograophic signal, where each FFT has a different time record of the signals such as a number of points, or a zero padded FFTs. The noninvasive photoplethysmographic sensor for mobile animals provides actigraphy measurements for the animal.
