Evaluation of a temperature remote sensing technique

A noninvasive technique for measuring temperature in hot gases is evaluated as an alternative to conventional mechanical probing techniques. The technique uses a diode laser spectrometer to measure the line-center absorption coefficient ratio of two absorption lines that originate from different vibrational energy levels of the same absorbing species. The temperature is calculated without knowledge of the total pressure, absorber concentration, or optical path length. A previous study demonstrated temperature measurements at ~2000 K at atmospheric pressure. The results of this evaluation demonstrate that the technique is also applicable for temperatures as low as 400 K and at pressures well below 1 atm.