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2018-05-09
3. Operating principle
The flow measuring principle is based on ultrasonic measurement method. The ultrasonic signal is transmitted alternately in either of the two
directions along the measurement part. The flow value is calculated from the transition time difference between the ultrasonic waves with
identical wavelength that was send in the right and opposite direction.
The working medium temperature is measured with standard Pt500 platinum resistive temperature sensors. Pairs of temperature sensors with
2-wire connection method for measurement temperatures on flow and return pipelines are used. Flow and return temperature sensors can only
be replaced on the factory-made pairs.
In normal mode the flow volume measurement is done every 1 second, and the temperature measurement, energy value calculation and refresh
of the values indicated on LCD are done every 16 seconds.
Energy calculation formulas:
flow sensor in supply pipe:
Q = V
1
× ρ
1
× (h
T1
- h
T2
)
flow sensor in return pipe:
Q = V
1
× ρ
2
× (h
T1
- h
T2
)
where:
Q – thermal energy
V
1
– water volume (m
3
)
Θ
1
– supply temperature
Θ
2
– return temperature
ρ
1
/ ρ
2
– water density at supply temperature Θ
1
/ return temperature Θ
2
h
T1
/ h
T2
– enthalpy at supply temperature Θ
1
/ return temperature Θ
2
When cooling energy measurement is enabled and the temperature difference is negative (supply temperature < return temperature) with the
value above 0.15 K then the cooling energy values will be written in the additional register:
∑Q = Q
1
+ Q
2
Q
1
– heat energy
Q
2
– cooling energy
flow sensor in supply pipe:
when Θ
1
> Θ
2
: Q
1
= V
1
×
1
× (h
T1
- h
T2
), Q
2
= 0
when Θ
1
< Θ
2
: Q
2
= V
1
×
1
× (h
T2
- h
T1
), Q
1
= 0
flow sensor in return pipe:
when Θ
1
> Θ
2
: Q
1
= V
1
×
2
× (h
T1
- h
T2
), Q
2
= 0
when Θ
1
< Θ
2
: Q
2
= V
1
×
2
× (h
T2
- h
T1
), Q
1
= 0
The meter's calculator provides all the necessary measurement and data storage functions.
4. Marking and sealing
4.1. Marking
4.1.1. Calculator
There are following information on the front panel of calculator: manufacturer's trade mark, meter type, temperature sensors type, calculator
temperature measuring range, calculator temperature difference measuring range, flow sensor temperature range, nominal/maximum/minimum
flow rate (q
p
/q
s
/q
i
), year of manufacture, connection type and size, nominal and maximum admissible working pressure, device ingress protection
rating, accuracy class, environmental class according EN1434-1, electromagnetic and mechanical environmental class, EC-type examination
certificate number, flow sensor mounting place (supply or return pipe), type of working medium and concentration (if other than water), serial
number and distributor's logo (if applicable).
The terminal pins numbers are marked close to the terminal which is inside the calculator.
4.1.2. Flow sensor
The flow sensor is marked with the following information: connection type to the pipeline (threaded connection – G, flanged connection – DN)
and size, the arrow for indication of a proper flow direction of working medium.
4.2. Security seals
The manufacturer provides the following security measures for the calculator:
the manufacturer's warranty seal preventing access to the adjustment activation jumper (see Fig. 12.1.);
the manufacturer's warranty seal on the fastener of the cover protecting electronic module (see Fig. 12.1.).
The manufacturer provides the following security measures for the flow sensor:
the seals on the screws of protective cover of flow sensor (see Fig. 12.2. - Fig. 12.4.).
After installation of the meter the installer shall mount following seals:
butterfly, wire or lead seals to bind the lid and bottom part of the calculator enclosure (see Fig. 12.1.);
