振动监测 > X20CM4800X > Function description > Vibration measurement

X20CM4800X - Data sheet V1.04

The data interface for the raw data is based on Flatstream communication. Operation takes place using library "AsFltGen".

Information:

Each channel has its own Flatstream.

For information about library "AsFltGen", see Automation Help.

The required bytes for transmitting the raw data at the Flatstream depend on the set sampling rate, the set data resolution and the bus cycle time used.

Information:

If the raw data is not transferred to the controller fast enough, it is buffered in the module per channel. As soon as the buffer is full, error message BufferOverflow occurs.

Calculation example for required number of bytes

The following settings are made for a measurement evaluation:

•Bus cycle time: 2 ms

•Sampling rate: 2 kHz (one value every 500 µs)

•Data resolution: 16 bits (2 bytes)

In the bus cycle time of 2 ms, this results in 4 values of 2 bytes each – a total of 8 bytes. The Flatstream data interface must be configured in accordance with this calculation.

If the bus cycle time is reduced from 2 ms to 1 ms, the number of bytes required for the raw data is reduced by half, i.e. 4 bytes. This means that other channels have more bytes available.

Setting the MTU size

The MTU size to be set for the Flatstream is equal to the calculated data bytes + 1 control byte. Therefore, the input MTU size must be configured to at least 8 + 1 = 9 bytes, or in the second case, to 4 + 1 = 5 bytes.

Since this is only the ideal value, reserve bytes must still be planned to compensate for any timing tolerances or communication errors. Otherwise, it could happen that not all data can be transferred in time, causing a buffer overflow at some point.