It is important that the instrument not only indicates spontaneous values, but for several hours recording data. This is the case for this device. The data can - unfortunately without instructions - be transferred to the PC with data cable and show almost exactly the course of oxygen levels. The one-button operation is elider not properly described. With trial and error you will find out that in order to change the setting, an indication on the display must be pressed longer. Conclusion: instructions bad device very well.
