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2019 WEINZIERL ENGINEERING GmbH
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W. Input B1: Rate of change
This counter is used to connect devices to the bus where the
rate of change is critical within a time interval, e.g. an anemome-
ter.
Scaling factor (Value per delta in base time span)
A floating-point value is to be entered here. It determines the
value by which the counter value is increased on every pulse
Time base
Here the time base of the rate of change can be specified:
-
Pulses per second (e.g. [m/s], [km/h])
Value from parameter Scaling factor is multiplied by 1
-
Pulses per hour (e.g. [kW])
Value from parameter Scaling factor is multiplied by
3600
Measurement time span
The measurement time span determines how quickly the counter
can react to changes. Therefore, a short sample rate should be
selected for fast processes (e.g. anemometer).
The rate of change is calculated using the 3 parameters men-
tioned above:
The device saves several meter readings per measurement
interval, scales it with the scaling factor * time base and divides it
by the measuring interval.
Datapoint type
The datapoint type of output object of the counter variable can
be selected here:
-
Floating point (16 Bit) - DPT 9
Group Object
Type KNX
Size
Direction
GO 23 Input B1: Rate of change
– Value
9.024
2 Byte
To KNX
-
Floating point (32 Bit) - DPT 14
Group Object
Type KNX
Size
Direction
GO 23 Input B1: Rate of change
– Value
14.056
4 Byte
To KNX
Send condition
This parameter can be used to determine how the current coun-
ter value is to be sent:
-
On read
No independent sending of the counter value by the
device. To read the counter value, the read-flag of the
group object has to be set.
-
On change
An additional parameter is displayed to select the min-
imal delta from the last sent value for sending a new
counter value
-
Cyclically
An additional parameter is displayed to configure the
sending frequency of the counter variable.
-
On change and cyclically
Both sending conditions are active.
Monitoring limit value
When limit monitoring is activated, the following object is dis-
played:
Group Object
Type KNX
Size
Direction
GO 24 Input B1: Rate threshold
– State
1.002
1 Bit
To KNX
When limit monitoring is activated, the following parameters are
displayed:
Limit value
Here you can edit the checked limit value. The data-
point type is the same as rate of change value.
Behavior on exceeding limit value
In addition to the limit value itself, it is possible to de-
termine whether the counter should transmit 0 or 1 via
the object if the limit value is exceeded.
Behavior on going below limit value
Here it is possible to determine whether the counter
should transmit 0 or 1 via the object if the counter vari-
able goes under limit value.
Example: Electricity meter with S0 interface
From the data sheet of the electricity meter it can be seen that
the device delivers 500 pulses per kWh. A device with constant
power of 1kW is connected to this current meter for one hour.
The scaled counter measures the energy consumed:
Scaling factor: 1 / 500 = 0.002 -> Output in
kWh
The counter for the rate of change measures the current power:
Scaling factor:
- Output in kW: 1/500 = 0.002
- Output in W: 1/500 * 1000 = 2
Time base: Pulses per hour
Measurement time span: 300 s
Example: Anemometer
From the data sheet of the electricity meter it can be seen that
the device delivers 4 pulses/s at a wind speed of 1 m/s.
The counter for the rate of change measures the wind speed:
Scaling factor:
- Output in m/s: 1/4 = 0.25
- Output in km/h: 1/4 * 3.6 = 0.9
Time base: Pulses per second
Measurement time span: 10 s
