A photoelectric component of a pulse Co-oximeter that is applied externally to a body part (e.g., a fingertip for adults, the hand or foot for neonates), for the transcutaneous multiwave measurement of carboxy-haemoglobin saturation (SpCO) and typically several other related parameters such as haemoglobin oxygen saturation (SpO2), methaemoglobin saturation (SpMet), haemoglobin concentration (SpHb), haematocrit, and pulse rate using light detection. Signals from the probe, produced by a light-emitting diode (LED) and a receiving detector, are used to calculate results which are digitally displayed on the Co-oximeter's computerized unit. This is a single-use device.