N32O
User's manual
24
Table 9
Mode
Functions of measuring inputs
Filtering
the waveform
(measurement
of
pulse
duration
)
Automatic
reset
External
functions
Keypad
control
Multiplication,
division
by
a constant
Averaging
of a
measurement
using moving
window
method
Measurement
of
additional
quantity
Symbol
Description
I1A
I1B
CNtF
Fast pulses counter
Counted pulses
Change of
counting
direction
+
1
+
+
-
2
-
CNt SL
Slow pulses counter
Counted pulses
Change of
counting
direction
+
3
+
+
-
2
-
PERIOD
Period measurement
Signal
-
+
1
-
+
+
frequency
FREQ
Frequency
measurement
Signal
-
+
1
-
+
+
period
tACHO
Rotation speed
measurement
Signal
-
+
1
-
+
+
frequency
ENC*
Incremental encoder
support
Signal A
Signal B
-
+
+
-
-
CNtFL*
Pulse counter with
pulse frequency
measurement
Counted pulses
-
+
1
+
+
+
4
frequency
W tIME
Working time counter
-
-
-
+
-
-
-
tIMER
Timer (seconds)
-
-
-
+
-
-
-
tIME*
Current time
-
-
-
-
-
-
-
* Measurement type available only for the main input.
1
Filtering is enabled if a given parameter (
tL
or
tH
) has been set for a time higher than 50 (the setting is expressed in microseconds)
2
Moving window averaging is disabled but the minimum and maximum values in the period defined by MAVG setting are registered.
3
Filtering is enabled if a given parameter (tL or tH) has been set for a value higher than 0 (the setting is expressed in milliseconds).
4
The measuring frequency is averaged using the moving window method in CNTFL measurement mode.
According to the table above, it is possible to filter the input waveform for several modes.
Filtering the waveform
is based on ignoring the occurring pulses which duration is
shorter than the filter setting. When selecting the filtering time, the set time should be
treated as a pre-setting, because the measuring waveform has many factors, e.g. input
signal amplitude, source signal type (rise and fall times), e.g. open collector output or
push-pull output. The graphical example of the filtering is shown in the figure below.
When using the filtering, it is important to keep in mind that the measurement of high level
of interference signal may have an additional error, especially during period, frequency or
their derivatives measurements. Nevertheless, filtering allows to make the correct
measurements of the signals with high level of interference, e.g. when measuring the
rotation speed, where the signal is generated by the inductive sensor and there are
several changes of the sensor output signal when the gear tooth approaches the sensor
due to insufficient hysteresis.