Portable Ultrasonic Flow Meter

RBHFM-P Portable Ultrasonic Flow Meter(flow measurement) is a full function portable transmit-time ultrasonic flow meter. It's new design to measure wide range pipes, from DN25-1200(1"-48") the pair of transducer with mounting. No matter you want to quickly verify the flow reading of another meter or to data log flow system values over an extended time period, the RBHFM is the suitable tool. The portable meter has the clamp on transducers no tapping or cutting is required, just clamp outside of the pipe. The meter can be easily moved and installed in different pipe and convenient to carry site to site.Its portability makes it an excellent choice formeasuring flows throughout the plumbing infrastructure to verify sensor, pump andvalve performance. RBHFM Portable Ultrasonic Flow Meter Clamp-On Ultrasonic Flowmeter High-quality, durable, and reliable. Applicable to all types of liquids that without air, sediment or sludge



  • Principle
  • Features
  • Specification
  • Model Selection
  • Applicants
  • Download

RBHFM Portable Ultrasonic Flow Meter  working Principle:

How an Ultrasonic Flow Meter Works

An ultrasonic flow meter utilizes ultrasound to measure the velocity of a fluid and is used in a variety of fluid applications. Ultrasonic flowmeters are ideal for water and other liquids. Clamp-on ultrasonic flow meters achieve high accuracy at low and high flows, save time with no pipe cutting or process shutdown, and are not affected by external noise.

Here’s how ultrasonic flow meters work.

Ultrasonic flow meters use sound waves at a frequency beyond the range of hearing (typically 0.5, 1, or 4 MHz). This ultrasound signal is sent into a stream of flowing liquid by using wetted (insertion) transducers that make direct contact with the liquid or external (clamp-on) transducers that send the ultrasound through the pipe wall. Clamp-on ultrasonic flow meters allow users to measure the volumetic flow rate of a fluid in a pipe without having to penetrate the pipe which decreases installation and maintenance costs.

A typical transit-time ultrasonic liquid flow meter utilizes two ultrasonic transducers that function as both ultrasonic transmitter and receiver. The ultrasonic flow meter operates by alternately transmitting and receiving a burst of ultrasound between the two transducers by measuring the transit time that it takes for sound to travel between the two transducers in both directions. The difference in the transit time (∆ time) measured is directly proportional to the velocity of the liquid in the pipe.

Below is a drawing of a typical application using the most common, V (2 pass) mounting method with clamp-on transducers. In this application, the ultrasound is transmitted from the first transducer and travels through the pipe wall, through the liquid, then reflects off the back wall of the pipe, then travels through the pipe wall, and is picked up by the second transducer.

The same process is then repeated in reverse as the second transducer transmits the ultrasound. The time difference between the times of flight up and down is the ∆ Time. When the liquid in the pipe is not moving, the ∆ Time would be zero.


To calculate the velocity of the liquid, you need to convert the raw ∆ Time into the velocity of the liquid in the pipe. The angle of the ultrasound path is calculated by knowing the speed of sound of the pipe and the liquid. This angle is used in a common trigonometry equation to convert the ultrasound path into a straight line in the pipe. This will be the velocity of the liquid in the pipe.

Once the velocity is known, it’s just a matter of converting it into a flow rate by multiplying it times the cross-sectional area of the pipe, as with any velocity based flow meter.

Why choose ultrasonic?

Ease-of-Installation: The largest benefit of any “clamp-on” transit-time flow meter is the ease-of-installation. While still requiring sections of straight pipe upstream of the measurement location, the process does not require shutting the system down to install, making maintenance and upkeep of transit-time meters much more attractive.

Low maintenance: There are no blades to wear out or bearings to replace as in turbine meters, nor are there electrodes that can foul over time as in magnetic flow meters.


The artical is from Dec 05, 2017


RBHFM-P Portable Ultrasonic Flow Meter(measurment) Features:

  • Only a pair Clamp-on Transducer to measure wide pipe range: DN25-1200(1"~48")
  • High accuracy: ±1% of measured value
  • Easy to install, reduced installation time and cost.
  • No pressure head loss, No moving parts to maintain or replace.
  • IP68 class Transducer.
  • BTU function is an option. 
  • Portable Flow Meter with Long Battery Life 16+ hours continuous operation
  • Built-In Datalogger 16GB of transmitter storage for log files and  also support the data sheet analysis software
  • Measures a Range of ParametersMeasure velocity, volume, mass, totalizer, energy flow rate measurements and more

RBHFM-P Portable Ultrasonic Flow Meter Specification:

Flow range

±0.03 ft/s ~ ±40 ft/s (±0.01 m/s~ ±12 m/s)


±1% of measured value

Pipe size



Single medium liquid

Pipe material

Carbon steel,stainless steel,PVC and other compact material pipe

Function specifications


Analog output: 4~20mA, Max 750 Ω .

Modbus: RS485

SD card



1 ~ 99999seconds

Key broad

Digital keys


240*128 back lit LCD

Power supply

Rechargeable Lithium Battery Power,3000mAh

(Continuous operation of main battery 16 hours).



Transmitter: -40℃~60℃

Transducer: -40℃~80℃ (-40℃~80℃ is standard; -40℃~130℃ is an option)


Up to 99% RH,non-condensing

Physical specifications




Encapsulated design,IP68

Transducer cable

Standard cable length: 5m (16ft).

Model Selection

RBHFM-P Portable Ultrasonic Flow Meter Model Selection:

The RBHFM Portable Transit time Ultrasonic Flow/Heat Meter Model Selction
RBHFM-P Code Type of Transmitter
  Ultrasonic Flow Meter
H Ultrasonic Energy/Btu Meter function( RTD)
  RBH Type of transducers(Pipe range: DN25-1200mm)
1 Clamp-on, IP68. Operating temperature: -40℉ ~ +176℉(-40℃ ~ +80℃)
2 Clamp-on, IP68. Operating temperature: -40℉ ~ +266℉(-40℃ ~ +130℃)
I Insertion, IP68. Operating temperature: -40℉ ~ +266℉(-40℃ ~ +130℃)
  Type of mounting track
S Single guide mounting type bracket
D Dual guides mounting type bracket
  Transducers cable length
5 D series type of cable Standard 5m (16ft) with mounting track.
X XX is the length you need for cables, Maximum lengthen to 30m.
  Temperature sensor
N Without
1 A pair of clamp on PT1000 sensor 9m
N Without
1 With SD card
Remark: Model selection sample:
1. standard configuration: RBHFM-F-1S5NN RBHFM series Portable Ultrasonic Flow Meter , RBH type transducer, -40℃ ~ +80℃, IP68 5m cables with single guide mounting track. Without tenperature sensor and datalogger.


RBHFM Portable Ultrasonic Flow Meter Application:

  • Cooling and heating water
  • Water leakage
  • Water distribution flow metering
  • Leak Detection
  • Wastewater flow-metering
  • Building Services
  • Inspection of fixed installation meters
  • Power/Energy Management
  • Chemical / Pharmaceutical
  • Petro-Chemical
  • Pump inspection
  • Food/Hygienic flow-monitoring
  • Steel
  • Light Industrial
  • Survey work
  • etc.


RBHFM Portable Ultrasonic Flow Meter catalog

RBHFM Portable Ultrasonic Flow Meter manual

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