KRAL BEM 300 Series, Руководство по эксплуатации

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6 OIE 15en Edition 2019-12 HW 2.0/SW 2.0 Operating Instructions
Volume measurement
Function description
Function description
With its functional scope the KRAL electronic unit covers a wide range of functions. The electronic unit is
optimized for use together with KRAL Volumeters. KRAL Volumeters generate a specific number of
pulses per flow volume unit - depending on the size and working point. This device-specific characteri-
stic is called the K-factor (unit: Pulses/Liter) and is listed in the enclosed calibration report.
The pulse signals of one volumeter can be evaluated. The following signals are available:
□
PNP
□
Namur
□
NPN
For push-pull pick ups either PNP or NPN can be selected.
In addition the devices can also be equipped with further pick ups for flow direction detection. The elec-
tronic unit is supplied with settings in accordance with the customer requirements.
Together with diverse options for signal transfer with analog, pulse and bus outputs this means that an
extensive scope of performance is available that offers the following main possibilities:
Volume measurement
The instantaneous value of the volume flow (volume per time unit) is calculated from the measured
value of the incoming pulses per time unit and the stored mean K-factor and is displayed. Furthermore
the total number of measured pulses can be used to display the total flow (volume) as a total value since
the device was last reset. Rate values represent the current instantaneous values, total values corres-
pond to the sums since the last resetting.
Mass calculation
The instantaneous value of the mass flow (mass per time unit) is calculated from the measured value of
the incoming pulses per time unit and the stored values of mean K-factor and mean density and is dis-
played. Furthermore the total number of measured pulses can be used to display the total flow (mass)
as a total value since the device was last reset.
Rate values represent the current instantaneous values, total values correspond to the sums since the
last resetting.
Averaging
A strongly fluctuating flow rate causes a jumping display or as a result a fluctuating analog output. The
averaging function reduces this effect by generating a mean value across several measured values. The
number of measured values for averaging can be set, see "2.07 Averaging analog output", page 31, and
see "2.12 Averaging display rate", page 32.
Flow direction detection
In extreme cases the flow direction can change through pulsations, meaning through liquid waves in the
piping system. By using two pick ups which generate square wave signals out of phase by 90° (square
wave encoder signals) a reversal in the flow direction is recognized and taken into account when calcu-
lating the total value.
The electronic unit offers incremental encoding inputs for each volumeter. This means that the flow
direction can be determined without additional components and taken into account in the calculation at
any time.