When using the oxygen indicator which rection from the needle should you expect as a sample is drawn into the instrument?

 When using the oxygen indicator which rection from the needle should you expect as a sample is drawn into the instrument?

1) rise to the correct reading and then slowly fall to zero as the oxygen in the sample is consumed
2) move back and forth and finally stabilize at the correct reading after about 10 seconds
3) slowly rise to the correct reading and then remain stationary

Ans___2) move back and forth and finally stabilize at the correct reading after about 10 seconds