Digital Oxymeter GMH 3691

The digital oxymeter GMH 3691 is now ready to use with the Arduino, and supposed to be integrated into the next version of Vanitas Machine…

Instead of the RS232 interface converter provided by the company a costom-made cable (less expensive) was used. Also, some adaptations needed to be made based on the interface description to be able to read out the device at all. Thanks to Martin Nawrath from Lab3!

After calibrating the devide based on ambient air I started to do the first tests and measurements today… I provisorically integrated the sensor into one of my previous test environments and measured the oxygen levels while burning a candle. In the course of about 10 minutes, without supplying fresh air, the oxygen level dropped constantly from 20,7% to 17,4%, which is when the candle went out. The temperature rose only slightly by 0,3 degrees C°. Interestingly, the oxygen partial pressure also changed a lot, which I will have to explore further. I guess that the results very much depend on the excact position of the sensor (the oxygen level seems to be generally higher the higher the sensor is positioned), so more experiments need to be made.