A system and method comprising a pulse oximeter with a pulse width modulator that periodically tests the en wavelengths emitted at the pulse widths upper and lower limits in order to ensure that the median pulse width is emitting the wavelength specified by the manufacturer. The system comprises a pulse oximeter that has LED emitter(s), photodetectors, a pulse width modulator and memory. The specifications database contains data relating to the wavelength specified by the manufacturer. The calibration software will periodically test the LED to ensure the correct wavelength is being emitted by the LED in order to detect the proper constituents in the patients blood. The testing is conducted whenever the pulse oximeter is energized and then again at a specified interval until power is disconnected from the pulse oximeter. Each test includes increasing the pulse width until an error is detected, recording the upper limit of the pulse width and the corresponding wavelength before an error occurred. Then performing the same test by decreasing the pulse width until an error is detected. The wavelength emitter at the median pulse width is then calculated and compared to the manufacturers specification. If they do not match the calibration software adjusts the pulse width until the manufacturers specification is achieved.
