Operation
22 Sensyflow
FMT700-P
42/14-42-EN
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5.4 Temperature
measurement
Installing an additional measurement resistor (Pt100) in the flowmeter sensor makes it possible
to measure the temperature of the air. With a nominal diameter of DN 25, the Pt100 is installed
in the inlet section.
To display the temperature of the fluid, press the "TEMP" button. Press the button again if you
want the unit to revert to its initial state (flow measurement).
Measuring principle
Using a transmitter, the Pt100's resistance signal is converted into a temperature-linear
4 ... 20 mA current signal while it is still inside the flowmeter sensor. It is then displayed as a
temperature in °C. If you need the temperature signal to undergo downstream electrical
processing, a jumper must be removed from inside the device (by the factory). In such cases,
the electrical circuit outside the device has to be completed using a display unit or recorder (for
example). The maximum permissible load is 120
Ω
.
During temperature measurement, the corresponding flowrate signal is
not
made available at
the interfaces.
Specifications for temperature
measurement using Pt100
Response times in air at v = 1 m/s
T
50
= 3 s
T
90
= 10 s
Measuring range -20 ... 100 °C (-4 ... 212 °F)
Measurement uncertainty under ambient
conditions ± 0.4 °C (32.72 °F)
G00940
8 8 8 8 8 8
T
E
Pt 100
1
2
3
4
5
Fig. 18: Gas temperature measurement
1
18 V (internal)
2
Display
3
Jumper (internal)
4
Transmitter
5
Analog output 4 ... 20 mA
The temperature-linear 4 ... 20 mA signal is made available (once the jumper has been
disconnected by the factory) at pins 11 and 24 (or 12 and 25 if operation involves the use of two
flowmeter sensors) (see section 3.4).
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