AM-ULM-EX Explosion-proof Ultrasonic Level Meter

An ultrasonic level meter times a pulse from a transducer above the liquid down to the surface and back. AM-ULM-EX is the version that may stand in a hazardous area: the datasheet prints the marking Ex db ia IIC T6 Gb, with GBT11828.4-2011 as the implementation standard and JJG971-2002 as the verification regulation. Span is 0–30 m, accuracy ±0.5 %, the display resolves 1 mm and the blind zone runs under 0.25–0.8 m with range. Two-wire and four-wire variants cover 4–20 mA, RS485 Modbus and a relay.

Its value is the certification, not the range, and the boundary follows from that. The table stops at atmospheric pressure, so a blanketed or pressurised vessel is outside it; foam, heavy vapour and a churning surface leave nothing to time; and no wetted material, medium temperature or chemical-resistance data is published, so the acid, alkali and hot service the introduction names cannot be signed off from the sheet. What the buyer gives up is the wetted side, and the datasheet is silent on it.