A Controllable DCCS-Based PT Temperature Sensor in High Precision Molecular Spectroscopy Application

In the high precision molecular spectroscopy, the temperature of gas absorption cell is accurately measured. In this paper we discuss the factors affecting the measurement accuracy of temperature sensor employing platinum resistance in a resonant quartz crystal tuning fork (QCTF) detector based wavelength modulation spectroscopy (WMS). A bridge temperature sensor powered by a dual constant current source (DCCS) is proposed. The DCCS was controlled to keep the constant current of 1mA in this work. Furthermore, we used the 3-wire measurements powered by DCCS to eliminate the impact of lead resistances and self heating of the platinum resistance so as to reduce measurement errors. A piecewise linearization model by linear approximation algorithm is employed to evaluate the measurement calibration and increase the measurement accuracy. Detection of trace methane (CH
₄
) was demonstrated using a near infrared distributed feedback diode laser near 1.653 μm and a single pass gas absorption cell with an optical length of 20 cm. An example of the temperature sensor employing Pt100 with 3-wire measurement is developed in the detection of CH
₄
with the temperature range from 0°C to 100°C. The controllable DCCS method is demonstrated by the measurement results of the deploying Pt100 sensors. Experimental results show that the accuracy of our proposed temperature sensor is improved in comparison with the conventional platinum resistance thermometer. The measurement accuracy is relatively increased due to employing the piecewise linear approximation model. The results also show good performance for measurement calibration, especially for high temperature region.