Hardware Manual COMBILOG 1020
54
Frequency Measurement
With frequency measurements the datalogger counts the pulses
within a certain time interval at the digital input. The user can pre-
set this time interval by setting the time base (TB) in the range
between 0.1 sec and 10 sec. The frequency is calculated by the
sensor module from the number of pulses and the time base
TB
as:
frequency f =
number of impulses per time interval TB
length of time intervall TB
Hz
With frequency measurements always the negative signal edge
(1
-
> 0) is counted.
The lower the frequency
f,
the larger the interval between two
pulses, and the larger the time base
TB
has to be. On the other
hand the updating of the measured value decreases with an in-
creasing time base. Thus the time base should be selected so as
to make
TB
≈
1/f
u
,
f
u
being the lowest frequency respectively the
smallest change in frequency to be determined by the datalogger.
The error with frequency measurements thus amounts to
∆
f = f
u
=
1/TB
.
Note:
The high-end frequency for the frequency measurement,
i.e. the highest frequency to be measured, depends on the inter-
nal clock frequency of the processor. It is 1100 Hz for the 5 MHz
version (low power version) and 2000 Hz for the 20 MHz version
(standard version).
Summary of Contents for COMBILOG 1020
Page 1: ...COMBILOG 1020 Datalogger Hardware Manual Version 3 09...
Page 2: ...Hardware Manual COMBILOG 1020 2 Issue 03 11 2005 Technical data are subject to change...
Page 4: ...Hardware Manual COMBILOG 1020 4...
Page 6: ...Hardware Manual COMBILOG 1020 6...
Page 12: ...Hardware Manual COMBILOG 1020 12...
Page 86: ...Hardware Manual COMBILOG 1020 86 Bild 8 1 Example Master Slave System...
Page 169: ...Hardware Manual COMBILOG 1020 169...
Page 170: ...Hardware Manual COMBILOG 1020 170...
