Thermal mass flowmeters like the Sensyflow FMT use the principle of heating a sensor element and measuring the heat loss to determine mass flow. The Sensyflow FMT has a wide measuring range, low pressure drop, and direct measurement of mass flow. It can be used for full load measurement and leakage detection with one instrument.

1. Thermal Mass Flowmeter Sensyflow FMT
Fundamentals & Measuring Principle
ABB ATPA Measurement Products VIK Gert van Bergen

2. Sensyflow FMT – Fundamentals
Overview
Overview
Physical basics
Measuring principle
Design and characteristics of the sensor
Calibration
Summary

3. Sensyflow FMT – Fundamentals
Overview of flow rate and flow metering principles
Flow Rate and
Total Metering Instruments
Closed Pipe Lines
Open Channels and
Free Surface Pipe Lines
Flowmeters
Rectangular
and V-Notch
Weirs
Venturi
Flume Meter
Electro magnetic
Flowmeter
Total Flow Meters
Totalizers
Flowmeters
Direct
(Displacement
Totalizers)
Indirect
(Displacement
Totalizers)
Volumetric Mass
Oval Gear
Meter
Oscillating
Piston Meter
Lobed
Impeller Meter
Turbine,
Rotary Vane,
Woltmann,
Spiral Gear
Meter
Vortex
Flowmeter
Swirl
Flowmeter
Differential
Pressure
Flowmeter
Variable Area
Flowmeter
Electro magnetic
Flowmeter
Ultrasonic
Flowmeter
Mass
Flowmeter
Coriolis
Mass
Flowmeter
Thermal
available
at
Sensyflow
FMT

4. Example: Air
V = 2.3 m3
T = 40 °C
p = 5.0 bar
n = 1.429 kg/m³
m = 14.29 kg
Vn = 10 m3
Tn = 0 °C
pn = 1.013 bar
n = 1.429 kg/m3
m = 14.29 kg
Normal condition Operating conditions
Sensyflow FMT – Fundamentals
Volume Flow – Mass Flow
=
m
V
The gas mass is constant and
does not depend on pressure and temperature.

5. Abstraction of heat from a heated body by an
enveloping gas flow (Hot-film Anemometer)
T between Rh and RT = constant
The loss of heat depends on the number of
molecules that collide with Rh
.
m: Mass flow
Ih: Heating current
Rh: Platinum thin-film resistor – electrically heated
RT: Platinum thin-film resistor – gas temperature
Sensyflow FMT – Fundamentals
The thermal measuring principle
Rh
RT
Ih
.
m

6. Sensyflow FMT – Fundamentals
The thermal measuring principle
.
m
Ih
Rh
RT
Abstraction of heat from a heated body by an enveloping
gas flow (Hot-film Anemometer)
T between Rh and RT = constant
The loss of heat depends on the number of molecules that
collide with Rh
m: Mass flow
Ih: Heating current
Rh: Platinum thin-film resistor – electrically heated
RT: Platinum thin-film resistor – gas temperature

7. heating
element
sensor for gas
temperature
Temperature sensor
for heater
CPU
.
m
T
Alarms,
Diagnostics
separate temperature sensor for
the heater element
direct measurement of
the gas temperature
Digital signal processing
fast response time < 0.5 s
But: outer sensor shape
identical to VT-series
Thermal Flow
Sensyflow FMT – Fundamentals
The DIGITAL measuring principle

8. 100 200 300 400 500
.
m / [kg/h]
Ih / [mA]
300
400
500
410
Sensyflow FMT – Fundamentals
Characteristic curve
.
The heating current Ih is a measure for the mass flow rate m
For ambient air
in a 40 mm pipe
approx.
280 km/h
20 km/h

9. Sensor element
Capillary
Wires
Hull
Sensyflow FMT – Fundamentals
Sensor construction and mechanical protection
Heat
Sectional view
Gas flow
Top view
Protection bar
The protection bars
defend the sensor from
damage by dirt and
other objects!

10. Sensor element
Capillary
Wires
Shealth
Sensyflow FMT – Fundamentals
Sensor construction and mechanical protection
Thin sensor element Small surface for dirt
Small sensor mass Quick response
Small flow restriction Low pressure loss
Heat
Sectional view
Gas flow
Top view
Protection bar

11. Sensyflow in a pipe DN40:
Measuring range: 0(3) … 450 kg/h Pressure drop: max. 3 mbar
0
20
40
60
80
100
120
140
Sensyflow FMT Vortex Orifice
0
50
100
150
200
250
300
Sensyflow FMT Vortex Orifice
Turn down ratio
1:x
Pressure drop
mbar
Sensyflow FMT – Fundamentals
Comparison: Measuring range and pressure drop
High turn down ratio start-up and full load measurement
with one instrument
Low pressure drop no additional energy costs

12. Sensyflow FMT – Fundamentals
Measuring Accuracy
0,00%
10,00%
20,00%
0 500 1000 1500 2000 2500
FMT500-IG
Orifice
Competitor

13. Member of ‚Deutscher KalibrierDienst‘
DKD with two calibration facilities
Calibration range: 1 … 8800 kg/h air
High accuracy: <0.3 % of reading
proven and certified by the German PTB
(physical and technical federal agency)
Calibration certificate included in delivery
Sensyflow FMT – Fundamentals
Flow Calibration DKD

14. Unique calibration bench for gas flow measurement
Certified for flammable and non-toxic gases ( e.g.
methane, hydrogen, carbon dioxide…)
High accuracy by PTB-approved references
Pressures up to 40 bar
Sensyflow FMT – Fundamentals
Calibation bench for process gases

15. Sensyflow FMT – Fundamentals
Summary
Full load
measurement
and leakage
detection with
one isntrument
No additional
energy costs
No additional
pressure and
temperature
compensation
necessary
Quick
process control
Wide
measuring
range
Short
response
time
Low
Pressure
drop
Direct
measurement
of mass flow