X20 system modules • Other functions • X20CM4810
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X20 system User's Manual 3.10
Factor = 100 / (sensor sensitivity in mV/g)
All characteristic values and values must be multiplied by the calculated factor. This also applies to the analog
characteristic values if the characteristic value calculation is enabled as well as for uploaded time signals and
amplitude spectra. Exempt from this are all characteristic values without any units, such as "KurtosisRaw", "Crest-
FactorRaw" and "SkewnessRaw". See section 4.26.2.2.11 "Characteristic value format" on page 2075.
4.26.2.3.3 Information about FlatStream
When using FlatStream in Function model 0 - Standard and Function model 1 - Fast master, the following must be
noted. The X20CM4810 changes the values in the FlatStream in every X2X Link cycle. To avoid missing anything
in the task, it is important to select a task cycle that is either the same speed and synchronous to the module's bus
or faster. This also applies to fieldbus connections between the CPU and bus coupler.
The maximum bus cycle time of 10 ms must not be exceeded since it is not possible to guarantee that the data
calculated by the module every 300 ms will be fully transferred on the bus.
4.26.2.3.4 Information about using a SG4 CPU
The X20CM4810 calculates all characteristic values up to "Vdi3832KtRaw", "Vdi3832KtHighFrequency" and
"CrestFactorHighFrequency" independently every 300 ms. Automation Runtime facilitates the handling of the mod-
ule for the user (characteristic value upload), scales the characteristic values to the sensor resolution and also
calculates the characteristic values specified above.
4.26.2.3.5 Calculating the velocity signal automatically
The X20CM4810 module can calculate the velocity signal from the signal provided by the acceleration sensor. This
calculation is disabled by default since it can reduce the accuracy of the acceleration signal.
Reason
When converting from acceleration to velocity, low frequency portions become very large. As a result, the autogain
is decreased by a few levels, which then further degrades accuracy.
If this calculation is not enabled, 0 is output for all characteristic values calculated on the velocity spectrum. The
characteristic value "ISO10816" is not affected by this.
4.26.2.3.6 Information about AutogainDelay and overflow
The X20CM4810 automatically adjusts the measurement signal dynamically (autogain) to ensure that it is mea-
sured with the highest possible accuracy. This adjustment is made in multiple steps. Each step amplifies the input
signal more than the last. If the signal was very small for a long time and a impact suddenly occurs, an overflow may
occur with some calculated characteristic values. This is indicated by the overflow bit for the respective channel
(Overflow01-04) being set and the affected module characteristic values being set to their maximum. See section
4.26.2.2.11 "Characteristic value format" on page 2075.
With Function model 0 - Standard, there are also the additional data points "OverflowCharacteristicValues01-04"
and "OverflowFrequencyBands01". These are automatically generated by Automation Runtime and directly indi-
cate the overflow status of the individual characteristic values and frequency bands.
If an overflow occurs or if an internal threshold is exceeded, the autogain for the next measurement is reduced by
one level. If no overflow occurs for a certain number of measurements (adjustable by "AutogainDelay01"), or the
signal stays below the internal threshold, the autogain is increased by one level again.
If overflows are occurring frequently, increasing AutogainDelay may help.
4.26.2.3.7 Important information when using a B&R Compact CPU or fieldbus CPU
Due to the size of the firmware for the X20CM4810 module, only CPUs with sufficient ROM (> 1MB) are supported.
(X20CP0292 or X20XC0292)