VPB1MPA is a modulated infrared optical level probe designed for direct detection of liquids in tank applications. It features a nickel-plated brass housing with a polysulphone tip that provides high chemical resistance to most acids and bases, and incorporates a built-in amplifier with PNP 4-wire output (NO & NC switching). The sensor operates using a refraction principle where a Ga-As diode emits modulated infrared light that is internally reflected when the tip is in air but refracted when immersed in liquid, making it insensitive to ambient light up to 50,000 lux. With a rated operational voltage of 10–40 VDC, continuous output current of =200 mA, and operating frequency of =30 Hz, the sensor delivers sensing accuracy of ±5 mm in horizontal mounting and ±2.5 mm in vertical mounting. This design is ideal for monitoring liquid levels in industrial tanks containing oils, waste water, and aqueous solutions without requiring additional accessories.