Measuring Water Flow Using Ultrasound

The bluebot water flow meter utilizes ultrasound to measure flow by clamping on to the outside of the pipe. The substantial benefit of this is flexibility because bluebot clips onto the outside of any Copper, PVC, Galvanized or PEX pipe from ¾”to 2” all with the same meter. No pipe cutting or water shutoff is needed.  All other water flow meters get bigger and more expensive the the pipe gets larger.

Transit-Time Technology

The bluebot is a Transit-Time ultrasonic flow meter and uses two transducers pressed onto the outside of the pipe that function as ultrasonic transducers. The bluebot flow meter operates by alternately transmitting and receiving a frequency-modulated burst of sound energy between the two transducers. By measuring the difference in the Transit-Time and knowing the liquid type and pipe size, the meter calculates the flow velocity and flow rate.

The following is a very straightforward explanation of the Transit-Time method of measurement. Two ultrasonic sensor transducers are used, one upstream and one downstream of the flow. The upstream sensor aims and transmits an ultrasonic signal through the pipe wall. The signal bounces off the bottom of the pipe where it is then received by the downstream sensor (imagine a V shaped sound wave.).

Next, the downstream sensor transmits a signal back to the upstream. This back and forth transmission of sound happens every nanosecond (one billionth of a second). The Transit-Time (time it takes the signal to transmit and be received) is measured very accurately by the bluebot electronics.

It just so happens that sound travels faster with the flow than against it. At zero flow, the upstream and downstream signal transmissions would be the same transit-time. When even the smallest flow occurs, the Transit-Time of the signal with the flow is faster than the signal against the flow. This difference in transit-time is proportional to the water flow rate. So in essence, bluebot measures time differences down to the nanosecond and translates them into an extremely precise and repeatable flow rate measurement.

Industry Proven Technology

Although Transit-Time ultrasonic flow meters have been relied upon in general industry for over 30-years, this proven technology used in bluebot has never been applied in such a universal way for residential and light commercial use. The bluebot mechanical design, with the ability to adjust the ultrasonic sensor angles to match various pipe sizes and types, is patented.

If you have any questions or would like to speak to a member of the bluebot team, contact us directly at or call/text (831) 275-2715 M-F 10 AM - 6 PM PST.