A portable, battery-powered, photoelectric device intended for the transcutaneous measurement and display of haemoglobin oxygen saturation (SpO2). The signals, typically produced by light-emitting diodes (LEDs) and a receiving detector in a probe, or directly built-in, are used to make the measurements using the principle of spectrophotometry. The oximeter displays the SpO2 values and may calculate/display other parameters, e.g., pulse rate, electrocardiogram (ECG). The device is typically applied to the fingertip or around the wrist; it may be used by healthcare facilities, emergency services, or in the home.