The Greyline Instruments PTFM 6.1 is a portable transit-time ultrasonic flow meter designed for challenging flow applications in industrial environments . Its portability, intuitive interface, and ease of setup allow for quick deployment. It is often used to measure the flow of clean fluids like water, chemicals, and oils from the outside of the pipe .

The PTFM 6.1's transducers can be mounted on a wide range of metal or plastic pipes, including carbon steel, stainless steel, ductile iron, PVC, copper, and pipes with bonded liners. Configuration is fast using the built-in 5-button keypad; after entering the transducer type, pipe material, OD, wall thickness, and fluid type, the meter displays the correct transducer separation distance. Once the transducers are installed with coupling compound, the PTFM 6.1 immediately begins to display, transmit, and totalize flow. On-screen diagnostics and signal waveforms provide instant validation of accurate performance .

The meter covers a velocity range of ±0.1 to 40 ft/s (±0.03 to 12.2 m/s) with an accuracy of ±1% of reading or ±0.0046 m/s (±1.5 ft/s), and ±0.25% repeatability and linearity. It features a bright 2.8-inch color TFT LCD display, a rechargeable Li-ion battery providing up to 15 hours of operation, and an IP67 rating. The included Greyline logger software for Windows allows for data analysis and report generation. NIST certification is available .