The BASI BULT200 Series is a liquid level transmitter based on ultrasonic technology that is suitable for many liquid and solid applications. Ultrasonic pulse signals are transmitted and reflected from the liquid or solid surface. The transmitter ‘listens’ for reflected signals (echoes) and measures the time-delay between transmitting and receiving. The distance to the liquid surface is automatically calculated using the computed time-delay. An integral temperature sensor continuously measures the air temperature around the transmitter. It then computes the speed of sound in air, automatically compensating the Distance for temperature effects. The distance measurement can be sent through the 4–20 mA output.