The Bently Nevada Velomitor CT Velocity Transducer, model 190501-21-00-04, is a specialized low-frequency sensor engineered for monitoring casing vibration velocity in cooling tower and air-cooled heat-exchanger fan assemblies operating at 90 rpm or higher (typically 100–300 rpm). Designed to detect common machine issues like unbalance and misalignment, 190501-21-00-04 accurately measures vibration amplitudes at target frequencies, plus vibrations from fan motors and speed reducers, by capturing rotor vibration transmitted to the casing.

The "21" in 190501-21-00-04 denotes a 3/8-in 24 to 1/2-in 14 NPT adapter, while "00" signifies a MIL-C-5015 connection interface and "04" confirms CSA/NRTL/C, ATEX/IECEx certifications for hazardous area use. Crafted from 316L stainless steel, it boasts a sensitivity of 3.94 mV/mm/s (±5%), a frequency response of 1.5 Hz–1 kHz (±3.0 dB), and an operating temperature range of -40°C to +85°C. Weighing under 297 g, it requires a mounting torque of 4.5 N-m ± 0.6 N-m for secure installation on bearing housings or casings.