A New Sensor for Temperature Measurement of Water by Laser Interferometry Technique

We previously developed a temperature measurement system using interferometry and used it to measure unburned gas temperature in an engine cylinder. In this study, a new sensor is proposed to determine water temperature. This sensor utilizes the difference in measurement length between two laser beams. Both are the test beams, and there is no reference beam. The two beams pass mostly through equal or closely arranged paths; therefore, the effect of mechanical vibration on the two test beams is expected to be very small. The laser beam was introduced through a selfoc micro lens (SML) into a polarization-maintaining fiber connected with a sensor part. The beam emitted from another SML was divided into two. Both beams enter a quartz block and are reflected at the corner to change direction by an angle of π/4. They then pass through the test section although the lengths of the two beams are different in the measurement region. This sensor was installed on a side wall of a vessel. Water was poured into the vessel and stirred with a hot magnetic stirrer. The temperature near the sensor was also measured with a thermocouple as a reference. The response of the thermocouple was enough to follow the change in water temperature because the speed of change in temperature is very slow. This paper focuses on the confirmation and evaluation of this system of temperature measurement. One feature of this sensor is that it minimizes the effect of the therma