User manual

6 Detailed descriptions of I/O modules | Digital frequency counter module UR20-2FCNT-100
379Manual u-remote1432790000/08/12.2015
Function frequency counting
Deningthemeasurementcycleperiod
You can dene the length of the measurement cycle period
for each channel within the output process data. As the
23bit value has a resolution of 1µs, values between 1µs
and 8.388.607µs can be dened. The measurement cycle
period must be long enough to detect at least one rising
edge.
Settingofinputlter
In order to suppress any distrubances you can parameterise
a digital input lter for each channel (filter frequencies and
respective pulse widths see "Overview of editable parame-
ter").
Start measurement
To start the cyclic measurement, you have to set the Bit
"Measurement start" in the control word of each channel
(QX9.0 and QX11.0 respectively).
Calcuation of results
The input process data Rising edges register the amount
of rising edges for each channel within the referring mea-
surement cycle period. Counting starts with the last rising
edge of the previous measurement cycle and ends with
the last but one edge of the current measurement cycle.
The time between rst and last counted edge is dened as
measured period. This is a 27-bit value with a resolution of
125ns and an precision of 1µs (valid value range between
0x00000008 and 0x7FFFFFF8).
11 2 3 4 2 3 4 5 1 2 3 4
0 100 200 300 400 500 600 700 800
Measurement cycle 1
Period duration 1 Period duration 2 Period duration 3
Input
Measurement
active
Measurement cycle period
t = 200 µs
Start frequency counter
Control word: Measurement start
Stop frequency counter
Control word: Measurement stop
Measurement cycle 2 Measurement cycle 3
time [µs]
Measurement cycle 4
1. Measurement:
Period duration: 1200
Rising edges: 4
Current period duration:
1200
*
125 ns = 150 µs
F = 4/150 µs = 26,7 kHz
2. Measurement:
Period duration: 1600
Rising edges: 5
Current period duration:
1600
*
125 ns = 200 µs
F = 5/200 µs = 25,0 kHz
3. Measurement:
Period duration: 1500
Rising edges: 4
Current period duration:
1500
*
125 ns = 187,5 µs
F = 4/187,5 µs = 21,3 kHz
4. Measurement:
Period duration:
2147483647 (0x7FFFFFFF)
Functional principle frequency counting
Due to its resolution the value has to be devided by 8 within
the control programm in order to get the current period du-
ration in microseconds. This value can be between 1µs and
16.777.215µs.
The frequency is being calculated programwise as follows:
Frequency F =
Rising edges in current period
Current measured period
In case there is no rising edge registred within a measure-
ment cycle the current period duration will be set to the ma-
ximum value of 16.777.215,875 µs.
If the current period duration as well as the rising edges are
registred as zero, the current measured period was too short
to register a rising edge.
Modifying the measurement cycle period
You can modify the measurement cycle period during a run-
ning measurement. In this case the new value is not valid
until the following measurement cycle, during the current
measurement cycle the old value will be kept.
Stop measurement
To stop the cyclic measurement, you have to set the Bit
"Measurement stop" in the control word of each channel
(QX9.1 and QX11.1 respectively). If the last measurement
cycle has not been run through completely, the current
measured period will be set to the maximum value of
0x7FFFFFFF, the rising edges will be set to zero.