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When using an ultrasonic detector in high-temperature environments, a dedicated high-temperature probe along with a high-temperature coupling agent must be employed to ensure measurement accuracy and device safety. Conventional ultrasound probes can withstand temperatures of up to about 50°C; exceeding this temperature may cause delamination or damage inside the probe. When the temperature of the material being tested is above 50°C, a high-temperature probe and a special coupling agent must be used: Types of high-temperature probes: Biconical probes and delay-line probes – these create thermal insulation between the probe crystal and the hot surface through delay-line materials, and are suitable for thickness measurement and flaw detection. The probe contact temperature can reach 260°C (500°F) or even 480°C (900°F), as in the DLHT series of delay line probes. Electromagnetic ultrasonic thickness gauges (such as DEU300) enable non-contact measurement and can be used in field environments up to 800°C, making them particularly suitable for materials that are difficult to measure, such as stainless steel. Selection of high-temperature coupling agents: Ordinary coupling agents (such as glycerin and propylene glycol) evaporate rapidly at temperatures above 100°C, so specialized high-temperature coupling agents must be used. For example: Ultratherm coupling agent is suitable for temperatures ranging from 260–540°C, while medium-temperature coupling agent G is suitable up to 315°C. Residues must be removed before each measurement to avoid affecting acoustic performance. Operational precautions: Control the working cycle to prevent the probe from remaining in contact with high-temperature surfaces for extended periods, which could lead to heat accumulation and damage. Keep the probe pressed vertically during measurement to ensure good contact. The ambient temperature of the instrument’s main unit should generally be kept between -30 and 75°C, to prevent extreme temperatures from affecting the electronic components.