Portable Thermal Energy Metering

The portable FLUXUS F601 Energy is specially designed for temporary heating and cooling Thermal Energy measurement, with all measurements – Flowmeter, Temperature, and BTU computer, contained in one device. Temperature and BTU calculations are done in accordance with EN 1434 Thermal Energy meter standard.

Like all measuring systems of the FLUXUS series, the F601 Energy measures the volumetric flow rate non-invasively via its clamp-on ultrasonic transducers. Simultaneously, temperature probes monitor the temperatures at the supply and return lines of the heating or cooling system. From the temperature difference as well as the measured volume flow rate and on the basis of the physical media parameters (liquid enthalpy data stored in the meter), the heating or cooling performance is calculated.

Further, the FLUXUS F601 Energy is equipped with two measurement channels to:

  • Simultaneously measure two pipes e.g. chilled and hot water submetering in a building, two chillers at the chiller plant, etc.
  • Allow for a complete monitoring of a chiller – chilled water and condenser water
  • to allow accurate measurements even at locations that have very little straight run – dual mount on one pipe averages profile disturbance.

Dual channel measurement on all supply and return lines of a heat exchanger for complete efficieny monitoring

An important advantage of the FLUXUS F601 Energy lies with its very high zero point stability and unrivalled accuracy even at very low flow rates.
In submetering it is necessary to capture very low flow rates during off peak seasons – like hot water delivery to a building in the summer months – or this becomes free energy. Many meters have zero drift that is hidden by a zero cut-off setting, and some metering technologies just cannot measure the low velocities associated with Thermal Energy off peak flow rates.

Another important aspect of the F601 Energy is, that every meter is WET FLOW CALIBRATED in a NIST traceable and ISO 17025 accredited flow calibration laboratory. This is a true calibration not a certificate of a bench tested meter that others might supply as an accuracy certification.

A critical and sometimes overlooked aspect of the BTU / Energy meter combined performance is the temperature accuracy. Unmatched RTD’s can have a 1o F uncertainty on the temperature accuracy. For a chilled water system with a delta T of 10F this can represent a 10% uncertainty (error) in measurement. FLEXIM RTD’s are 4-wire matched pair with an extremely high match of 0.03F at 50° F (chilled water temperature). FLEXIM also adheres to EN 1434 for temperature accuracy for the full range of temperature measurement.

As all of FLEXIM's portable flow meters, the F601 Energy's ergonomic design offers simple handling and maximum ease of use. Its internal Li-Ion battery allows for more than 14 hours of autonomous measurement. Algorithms such as the correction of pipe wall echoes and transducer positioning errors ensure reliable and accurate measurement even in the most demanding application conditions.


  • The ideal portable measuring device for complete energy efficiency tasks (e.g. according to DIN ISO 50001)
  • Non-invasive measurement for precise bi-directional thermal energy flow rates
  • Ideal for inner pipe diameters ranging from DN6 to DN6000
  • Portable, easy-to-use flow transmitter with 2 flow channels, multiple inputs/outputs and an integrated data logger with a serial interface 
  • Automatic loading of calibration data and transducer detection reducing set-up times and providing precise, long-term stable results
  • Li-Ion battery providing more than 14 hours of measurement operation
  • Proven clamp-on technology, transducers resistant to dust and humidity
  • Probe for wall thickness measurement available
  • QuickFix for fast mounting of the flow transmitter in difficult conditions


Technical Facts

Measurement uncertainty at the measuring point (volumetric flow rate)
Measurement uncertainty of the measuring system (volumetric flow rate)
Flow velocity range
0.03 ... 80 ft/s for liquids
Ex zone transmitter
Power supply
Available transducers
for pipe sizes range
for temperature range
2 x current, 2 x binary
up to 4 x Pt100 / Pt1000, independent input adapter available