4 Function description
3.6 Ambient conditions
3.6 Ambient conditions
Parameter
Unit
Data/value
Storage temperature min. – max.
[°C]
-20 ... +80
Operating temperature min. – max.
[°C]
-20 ... +70
Humidity (relative humidity, non-condensing)
[%]
97
EMC emitted interference/immunity to interference
EN 61326
Vibration
o
EN 60068–2–47
o
EN 60068–2–64
Shock
EN 61373
Isolation min.
[V]
500
Degree of protection
IP 65
Tab. 5: Ambient conditions
3.7 Accessories
Notice
The technical data of the accessories are specified separately
4 Function description
4.1 Functional principle
4.1.1
Usage
The electronic unit is provided for usage with a KRAL flowmeter.
Flowmeters generate a specific number of pulses per flow volume unit - depending on the size and
working point. This device-specific characteristic is called the K-factor (unit: Pulses/liter) and is spe-
cified on the calibration certificate.
The pulse signals of up to two flowmeters can be evaluated. Pulse inputs for pick ups with the following
functions is available:
o
NPN
o
PNP
o
Namur
Either NPN or PNP can be selected for push-pull pick ups. In addition the flowmeters can also be
equipped with temperature sensors and further pick ups for flow direction detection. The electronic unit
is supplied with settings in accordance with the operating data.
4.1.2
Volume measurement
Each positive edge of the pulse signal starts a period measurement and at the same time stops the
previous measurement. The flow rate is then calculated via the frequency (= inverse of the period dura-
tion) and the K-factor. The inverse of the K-factor is the pulse value in I/P. This is retroactively added to
the total sums for each positive edge of the signal.
4.1.3
Mass calculation
The volume can be converted into mass via a configurable fixed density value (menu 4).
4.1.4
Linearization
However, the K-factor of a flowmeter shows slightly different values at different flow rates. These are
documented in the enclosed calibration certificate. In order to improve the measuring precision these
different values can be taken into consideration by means of a "Linearization". To do this the K-factors
are saved for a maximum of seven interpolation values. The K-factor relevant for the flow rate being
measured is then determined with linear interpolation between the two nearest interpolation values.
The linearization is used when the liquid lies within the low-viscosity range. The usage of the resulting
K-factor is recommended at viscosities exceeding 20 mm
2
/s. The resulting K-factor is determined as
the average value of the calibration points at the five higher flow rate values.
10
OIE 12en-GB Edition 2020-03
Operating instructions