High-accuracy ultrasonic temperature measurement based on MLS-modulated continuous wave

• A promising method for accurate ultrasonic temperature measurement is proposed.
• The obstructive effect of echoes can be suppressed by using MLS-modulated CW.
• Incorporating cross-correlation with PS is a promising method for TOF estimation.
• In our experiments, the temperature errors consistently remain within ±0.04 °C.

Ultrasonic temperature measurement has the potential to improve measurement accuracy by increasing the length of a received signal due to its excellent performance with noise resistance. However, when the distance between the transmitter and receiver is limited, the received signal can be polluted by strong multiple echoes, which can significantly degrade temperature accuracy. This paper proposes a method for high-resolution ultrasonic temperature measurement. With the use of a maximum length sequence (MLS)-modulated continuous wave, the obstructive effect of echoes is effectively suppressed. A hybrid method is employed for accurate time-of-flight (TOF) estimation by incorporating both cross-correlation and phase shift (PS), which is the basis of highly accurate temperature measurement. The experimental results in distilled water show that the proposed method estimates TOF with a standard deviation of less than 0.3 ns, and temperature errors consistently remain within ±0.04 °C.

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