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To address the high-viscosity conditions that occur during the washing or sedimentation of red mud, ultrasonic density meters (especially those based on acoustic impedance) rely on four key technologies to ensure accurate and stable measurements: 1. Core principle: Acoustic impedance matching technology. Ordinary ultrasonic flowmeters or concentration meters may depend solely on \"sound speed\" to determine density, but in high-viscosity media, the variation in sound speed is no longer linear. The acoustic impedance densitometer measures the reflectivity of sound waves at the interface between the probe and the medium (acoustic impedance Z=ρc). Acoustic impedance is directly related to the density and sound speed of a medium. Even when the viscosity of the red mud slurry is very high, resulting in increased sound wave attenuation, impedance technology can still accurately determine the density value by measuring the intensity of the energy reflected back from the interface. It is not sensitive to the rheological properties of the medium (viscosity changes), and focuses only on the \"overall acoustic properties of the solid-liquid mixture\". 2. Hardware design: High power and low frequencies for penetrating high viscosity generally mean that the medium has a very strong ability to absorb and attenuate sound waves. Ultrasonic waves with lower frequencies (such as 1 MHz or lower) are preferred, as low-frequency sound waves have greater penetration in viscous media and experience less attenuation. Increase the energy of the transmission pulse to ensure that sound waves can penetrate the highly concentrated red mud slurry and be clearly detected by the receiver, thereby maintaining a good signal-to-noise ratio. 3. Algorithmic compensation: Intelligent filtering and signal analysis. The high viscosity of red mud is often accompanied by non-Newtonian fluid properties (such as thixotropy), and it tends to trap bubbles. ①The linear frequency modulation analysis of acoustic impedance densitometers is an advanced signal processing technique. It does not focus on a single frequency, but rather emits a waveform with varying frequencies, and uses algorithms to analyze the echoes. This can effectively distinguish between “high-viscosity liquids” and “scars attached to the probe,” preventing reading drift caused by residue buildup. ②High-viscosity fluids tend to trap bubbles and are difficult to discharge. Ultrasonic densitometers use algorithms to identify the abnormal acoustic impedance signals caused by bubbles (gas has an extremely low impedance), automatically eliminate them, and calculate only the true density of the solid-liquid phase, thereby avoiding artificially low density values resulting from bubbles. 4. Structural design: Wear-resistant ceramics and anti-adhesion designs help prevent high-viscosity fluids from adhering to the surface of the instrument, thus avoiding the formation of a false layer of medium on that surface. The probe surface of the acoustic impedance densitometer is made of high-purity alumina ceramic or sapphire, which features a high Mohs hardness and an extremely smooth surface. High-viscosity red mud is difficult to adhere firmly to its surface, and even if it does adhere, it is easily washed away by fluids. In simple terms, to deal with the high viscosity of red mud, ultrasonic density meters do not rely on brute force; instead, they use \"penetration\" (low frequency and high power), \"sensing\" (the principle of acoustic impedance), and \"computation\" (intelligent algorithms). It doesn’t care how “sticky” the red mud is; it only cares about what changes occur to sound waves as they pass through this viscous substance. This makes it far more reliable in applications such as red mud washing, which are characterized by viscosity and abrasion, compared to fork-type density meters that rely on vibration principles (prone to sticking and resulting frequency changes) or density meters that rely on pressure differences (with the pressure sensing tubes at risk of getting clogged).