The accuracy of the oximeter is good. Pulse oximeter accuracy is the highest at saturations of 90-100% and lowest at 80%. The correct way to utilize an oximeter is to rest your body prior to use, before using the device. The oximeter is placed on the middle or index finger, of the body. The highest reading, should be recorded after about 5 seconds. The best finger to use with the oximeter is the middle finger, this is best for light. The two readings are the normal spo2 range.