Fixed, Clamp-on, Transit Time Ultrasonic Flow Meter

The Permaflow® is a fixed, clamp-on, ultrasonic transit time flow and heat meter that is non-invasive for measuring the flow rates of liquids containing less than 10% of gas/solid contents. It is mains powered, designed for 24/7 monitoring and is accurate to +/- 0.5% of measured value under ideal conditions.

P/N: 3578010-FLOW

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Clamp-on Fixed Ultrasonic Flow & Heat Meter

The Permaflow® fixed ultrasonic transit time flow meter has been tested and calibrated at an ISO 17025 laboratory, capable of meeting accuracies of +/- 0.5% of the true flow rate. We strive to offer the highest quality instruments, built with exceptional quality materials in the UK and remain competitively priced in the market worldwide through our unique R&D position. 

The different types of flow measured by the Permaflow are:  

  1. Volumetric Flow Rate: such as litres per hour (l/h) or gallons per minute (gpm) etc. 
  2. Mass Flow Rate: such as kilograms per hour (kg/h) etc. 
  3. Heat or Energy Flow Rate: such as kilowatt hour (kWh) or British Thermal Unit (BTU) 

All measured values can be individually totalised giving you the total flow rate that has been measured during a particular measurement session. 

The system accepts PT100 thermometer inputs, allowing temperature of your liquid to be monitored simultaneously. Two PT100 thermometers can be installed in order to monitor supply and return temperatures, commonly used in heating and chilling efficiency calculations. The system displays the measurements in various measurement units (metric and imperial options available), such as litres per hour (l/h) and gallons per minute (gpm) for flow rate, kilowatt hour (kWh) and British Thermal Unit (BTU) for energy and heat quantity. 

The system is built with modular I/O modules, with a range of different options available, allowing you to choose only what you need to save you cost and money. It comes with USB and RS232 as standard for serial communications and 16MB internal memory that is capable of logging over 90,000 measurements. It is capable of saving measurements internally, to be exported later to a PC, or data stream directly from the system to the PC. To help to achieve reliable measurements, the system comes with built-in oscilloscope for signal diagnostics that assists you in performing a reliable measurement as part of the setting up process. 

Some of the key advantages of Permaflow® over our competitors: 

BUILD QUALITY: Our ultrasonic flow sensors are made using a special composite material to optimise ultrasound transmission. 

BUILT-IN OSCILLOSCOPE: All units come with built-in oscilloscope for signal diagnostics that assists you in performing a reliable measurement as part of the setting up process 

PT100 THERMOMETER INPUTS: It has a unique ability to incorporate PT100 thermometer inputs so heat quantity measurement can be monitored alongside volumetric flow rates.  

HEAT-METERING CAPABILITIES: Due to its PT100 thermometer input integration, when Permaflow® is installed in heat networks or buildings for example, it is able to help comply with regulations by recording heated or chilled water flow rates, supply and return temperatures and calculate the thermal energy involved in heating and cooling the fluid to give an idea of energy consumption (for example in kWh or BTU units etc.) 

DATALOGGING & COMMUNICATIONS READY: Connection to PC is available as standard using both built-in USB and RS232, all measurements can be logged in its 16 MB built-in memory 

ISO 17025 CALIBRATION: Option to include ISO 17025 calibration certificate to verify the accuracy of your unit, we work closely with an established ISO 17025 flow laboratory in the UK to ensure our equipment meets your requirements 

Some of our main specifications (please see technical specifications below for full breakdown): 

  1. Works on pipes DN15 – DN 2500 
  2. Works on most clean liquids 
  3. Works on a wide range of pipe materials 
  4. Accurate to +/- 0.5% under ideal conditions  
  5. Measures flow velocities between 0.01 m/s – 25m/s 
  6. Resolution of 0.25mm/s 
  7. Repeatability of 0.15% of measured value 
  8. Main units rated IP65 
  9. Sensors rated IP66
  10. Sensors temperature range -20°C to +150°C 
  11. Datalogging function included – all measurement values can be logged in internal memory of 16 MB
  12. USB and RS232 communications included as standard 
  13. Large internal database of pipe, fluid and lining materials (19+ for fluids, 23+ for pipe and lining materials) 

Main benefits of choosing non-invasive ultrasonic transit time technology over inline flow measurement technology: 

  1. Clamp-on therefore no installation costs such as drilling into pipes and no downtime to the pipe network is present
  2. 24/7 flow rate monitoring and customisable alert options are available
  3. As there is no contact with the fluid being measured, there is no risk of pressure loss throughout your pipe network
  4. As with above, the fluid cannot damage the flowmeter, which could contribute to a longer lifespan and lower maintenance cost compared to inline flowmeters which are in contact with the fluid and risk being damaged by the pressurised flowing fluid
  5. The Permaflow® can be wall-mounted / fixed to achieve a stable and neat installation, allowing the display and measurements to be viewed clearly in a variety of room conditions 


What's In The Box

  Permaflow® Main Unit (RS232 and USB communications included):Main electronic unit
  Mains Power Supply:Supplies 12V – 36V DC to the main unit (suitable for mains AC power 100V – 240V)
  Pair of Standard Sensors (Model No. DM10) for pipes DN15:DN700 with 3m length cable (set of 2) – Compact, ultrasonic flow measurement sensors
  Pair of Jubilee Clips for your pipe sizes (set of 2):Strong, metallic bands suitable for more permanent fixture of your sensors
  USB Cable:For connecting the Permaflow® to your PC for direct download or export of logged data
  Measuring Tape:For measuring the distance between flow measurement sensors during set-up process
  Ultrasonic Couplant:For ensuring good contact between sensors and pipe wall
  User Manual:Contains further information regarding functionality of the instrument and how-to-use
  Installation Manual:Contains further guidance on how to install the flow measurement sensors on the pipe
  Calibration Certificate:As evidence that the unit has been tested and shown to be working before dispatch

Technical specifications

Technical Specification
  • Height: 160mm
  • Width: 82mm
  • Depth: 30mm
  • Weight: 300g
Pipe Diameter Range

Standard Sensor (Model No. DM10):  
DN15 – DN 700 (1/2” – 28”) 
Large Sensor (Model No. DS10):  
DN25 – DN2500 (1” – 98”) 
Works on a large variety of pipe materials (built-in database over 12+ materials) 

Liquid Types

Most clean liquids with gas/solids less than 10% volume (built-in database over 19+ liquids) 


+/- 0.5% of measured value under ideal conditions 

Flow Velocity

0.01m/s – 25 m/s


0.25 mm/s


0.15% of measured value 

Turn Down Ratio


Measurement Rate

1 Hz as standard

Measurement Units

Flow Velocity (m/s), Volumetric Flow Rate, Mass Flow Rate, Energy Flow Rate / Heat Quantity, Volume, Mass, Energy – also suitable for heat metering applications 


Full 240 x 160 pixel graphics with backlight

Additional Features

Signal oscilloscope for sensor positing and diagnostics 

Datalogging and Communication
  • 16 MB datalogger included as standard – all measurement values can be logged 
  • Serial Communications RS232 and USB included as standard, can be used for device control (command line interface) and datalogger download via PC 
  • 4 – 20 mA, Digital, Modbus, Relay, OPTO, Open Collector Output available as optional plug-in modules 
Optional Plug-in Modules
  • PT100 Thermometer Input (thermometer not included) 
  • 4 – 20 mA Current Input 
  • 4 – 20 mA Current Output 
  • Digital Input 
  • Modbus RTU 
  • Relay Output 
  • OPTO Output 
  • Open Collector Output 
Power Supply

2V – 36V DC configurations at 10W, DC PSU supplied as standard (suitable for mains AC power 100V – 240V)  

Operating Temperature
  • Main Unit: -10°C to +65°C  
  • Sensors: -20°C to +150° C   
IP Rating
  • Main Unit: IP 65 enclosure 
  • Sensors: IP 66 
Sensor Dimensions
  • Standard Model No. DM10: 40mm (L) x 20mm (W) x 25mm (D) 
  • Large Model No. DS10: 60mm (L) x 30mm (W) x 35mm (D) 
Sensor Material
  • Housing: Stainless Steel 
  • Front Face: PEEK (Polyetheretherketone) 
Cable Length

3.0m as standard (additional lengths available upon request) 


CE, Coltraco is ISO 9001:2015 and ISO 14001 approved 

  • Main unit – 3 Year Warranty
  • Sensor –  1 Year Warranty
  • Technical Support – Lifetime of the unit

See the Permaflow® in action.

Frequently asked questions

The Permaflow® works on a variety of different fluid types, as long as the speed of sound in the fluid is known. There is a built-in database of over 19+ fluids ranging from: water, sea water, kerosene, petrol, fuel oil, crude oil, Freon R134a, Freon R22, diesel oil, castor oil, F-76 fuel oil, Novec™ 1230, glycol/water, etc. There is an option to input custom fluid types as long as you know the speed of sound in the fluid – this can be found from online databases The Permaflow® will also work on a variety of pipe material, as long as the speed of sound in the pipe material is known. There is a built-in database of over 12+ pipe material ranging from: carbon steel, stainless steel 304, stainless steel 316, cast iron, ductile iron, copper, PVC, lead, nylon, PE, aluminium, asbestos, fibre glass, etc. There is an option to input custom pipe materials as long as you know the speed of sound in the pipe material – this can be found from online databases
The Permaflow® will work on pipes ranging from DN15 – DN2500 (1/2” – 98”). It is recommended that you notify us with the range of pipes you will be testing so we can allocate the appropriate sensor type for your application The Standard Sensors (Model No. DM10) will work from DN15 – DN700 (1/2” – 27”) The Large Sensors (Model No. DS10) will work from DN25 – DN2500 (1” – 28”)
The Permaflow® has 16MB of internal storage and it is capable of storing about 90,000 measurements. This is roughly equivalent to storing one measurement every second for just over one full day The logging interval can be set between 1 and 255 seconds Once the internal memory is full, the logging process continues but will begin replacing the oldest measurement first At its longest logging interval i.e. 255 seconds, the internal storage will be full in about 9 months before it will begin replacing the oldest measurement
Internal saved data can be transferred to a PC using the supplied USB cable and a serial terminal software. There are a range of different serial terminal software available online and Coltraco are able to recommend a few options if you are unfamiliar with this The Permaflow® is capable of transferring data directly to a PC via the USB port. Data can be streamed out of the Permaflow® using a serial terminal software which is freely available online
The Permaflow®The Permaflow® is capable of measuring energy consumption by monitoring the temperature of your fluid and measuring the flow rate of the fluid. The PT100 thermometer integration capability of the Permaflow® enables you to monitor the supply and return temperatures, together with the volumetric flow rate to calculate energy consumption. The values can be displayed in suitable units such as kilowatt-hour (kWh) and British Thermal Units (BTU). These data can be logged internally and downloaded to a PC. There are also other communication options available such as 4 – 20 mA, that can be customised to suit your requirements.
The accuracy and reliability of the Permaflow®’s flow measurement is dependent on your flow profile and how full the pipe is with your fluid To achieve maximum accuracy and reliability, the pipe needs to be full with the fluid during measurement The Permaflow® will work in fluids with up to 10% of gas or solid content. If your fluid contains a larger amount of solid content, a Doppler ultrasonic flow meter may be more suited for the application
If the paint layer is thin and in good condition, the Permaflow® will work well on the painted surface If the surface of the pipe is corroded, or the paint layer is thick, it is generally recommended to remove the paint layer before measurement is taken
The Permaflow® clamps on the pipe and and is non-invasive which means there are no installation costs such as drilling into pipes and no downtime to the pipe network is present As there is no contact with the fluid being measured, there is no risk of pressure loss throughout your pipe network As with above, the fluid cannot damage the flowmeter, which could contribute to a longer lifespan and lower maintenance cost compared to inline flowmeters which are in contact with the fluid and risk being damaged by the pressurised flowing fluid

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