Paul Wegener PWBlogg, Руководство по эксплуатации, Страница: 7 / 16

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The setting „permanent limit value monitoring“ means permanent sampling in interval 2. This leads to an im-
mediate identification of threshold violations. Thereafter, the memory interval 1 will be redirected to interval 2.
Please note that frequent sampling of transducers increases power consumption of data logger and decrea-
ses economic life-time of the battery!
Shorted alarm storage
In case of a threshold violation normally data recording will be continued with interval period 2. The period of
data recording can be much shorter than expected. To avoid it, the option „shorted alarm storage“ can lower
that period of time where interval 2 for storage is used. The storage is limited to a maximum of 2 x interval
1 (eg 2 x 5 min). Subsequently, it is continued to measure in interval 2 but recorded just with the cycle of
interval 1.
Password protection
The configuration can be protected via password against unauthorized access. Without knowledge of pass -
word, it is not possible to clear stored data or to change configuration of the data acquisition system.
2.2 Error sources
The analog signals of transducers are converted into a digital value with resolution of 8 bit, 12 bit, 14 bit or
16 bit. The following table demonstrates the difference between resolutions by means of a 16 bar transducer.
The values, represented in PWB-Soft program or on LCD must be rounded to the defaulted number of deci-
mal places so that the increment between two neighbouring values is not always identical.
Table: AD conversion, resolution
Potential error sources are non-linearities of AD converter which are irrelevant on resolution of 8 bit or 12
bit. However, another important one is the digital step at small resolutions. At the limit of two sequent digital
values, the tolerance between the measured (in digital steps presentable) and the real value (other sources
of error excluded) already amounts ½ resolution step. As in the table 8 bit is equivalent to 31,25 mbar. Additio -
nally, there are device-dependent sources of error such as temperature drop or deterioration of components.
At resolutions as 14 bit and 16 bit, they have much importance.
Operating manual of data acquisition system PWBlogg
ADU digital steps reading resolution
8 bit 256 62,5 mbar
12 bit 4096 4 mbar
14 bit 16384 1 mbar
16 bit 65535 0,25 mbar