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KDTIN input. While emission of KdT pulses a passive
gate signal is available on screw terminal KDTGATE.
KdT signals on the screw terminals:
KDTIN
KDT_GATE
KDTOUT
The number of generated KdT pulses corresponds to the
integer part of 100 times the KdT value measured by the
meter:
=
N
Int
(
100
K
dT
with
N:
Number of KdT pulses
heat coefficient in kWh K
K:
dT:
Temperature difference between supply and return in K
In addition to the generation of KdT pulses the displayed
volume and energy indexes are incremented. The
volume increment is equal to the pulse value PI (see
table above for numerical values). The energy increment
can be calculated using the following equation:
N
PI
kWh
=
dE
3
100
m
with
dE:
Energy increment of a volume pulse in kWh
N:
Number of KdT pulses
PI:
Pulse value in m³ (see pulse value table above)
VOLUME TEST VIA DISPLAY
To reasonably test the flow meter subassembly using
the display it should be in KdT mode because in this
state the volume display is set to high resolution and is
incremented in steps of the pulse value PI. No external
connections are required as long as the interface is
powered by the internal battery.
This test is usually done in standing start/stop conditions
to allow visually reading the index. The flow meter error
can be calculated by comparison of the volume
increment on the display to the reference volume.
ENERGY TEST VIA DISPLAY
In order to test the complete meter by means of the
display it has to be set to KdT mode. In KdT mode the
energy display is set to high resolution and is
incremented in steps of the energy increment dE. As
long as the interface is powered by the internal battery
no external connections are required.
This test is also commonly done with standing start/stop
to ease index reading. The meter error can be
determined by comparison of the total energy increment
on the display to the reference energy.
3
m
)
kWh
m
-1
-3
VOLUME TEST VIA INTERFACE
For flow meter subassembly testing through the
interface it must be in volume pulse mode. The interface
has to be powered internally or externally, VOL_PULSE
must be pulled-up and the test device has to be
connected at least to VOL_PULSE and GND.
In this configuration the interface passes volume
proportional pulses created by the flow meter to the test
device. The test device calculates the flow meter error
by comparison of the volume derived from the number of
received pulses and their pulse value PI with a reference
volume.
This test typically utilizes the flying start/stop method
with pulse synchronization and is recommended to get
accurate results at moderate testing times.
KDT TEST VIA INTERFACE
In order to test the combined subassembly consisting of
calculator and temperature sensor pair using the
interface it has to be in KdT mode. The interface must
be powered internally or externally, KDTIN and KDTOUT
have to be pulled-up and the test device must be
connected to at least KDTIN, KDTOUT and GND.
KDT_GATE is optional and if used has to be pulled-up,
too.
In KdT mode the interface passes a trigger pulse from
the test device to the meter and a gate signal as well as
a number of KdT pulses from the meter back to the test
device. By counting those pulses and comparing their
related KdT value to the KdT reference the test device is
able
to
determine
subassembly.
ACRONYMS
K
Heat coefficient
dT
Temperature difference
KdT
Product of K and dT
PI
Pulse value
N
Number of KdT pulses
dE
Energy increment
Int()
Integer part of term in brackets
7
the
error
of
the
combined
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