CANHEAD enhancements
74 A01185_11_X00_00 HBM: public CANHEAD
Added to the filter delay time is a latency time for CAN bus transmission. This
is 1/(maximum possible data rate).
Example: The transport time required for 6 modules at 500 kBaud is 10 ms.
The following applies to the data rate and filter selection:
S The 3 dB cut‐off frequency should be below the data rate by at least
factor 6
S Selecting a data rate above the internal sampling rate only wastes re
sources, the same measured value is then transmitted many times
S The data rate and the sampling rate should have integer divisors, so that
samples cannot be duplicated or omitted
Example:
Measurement with 12 modules (120 channels), 0.6 Hz filter and 20 S/s data
rate. If loading follows a ramp, then of 80 measurement points, internal
sampling only takes place 75 times; the same value is transmitted in duplicate
5 times. Every 16 measured values or 0.8 seconds, a duplicate appears in the
ramp. The data rate 18.75 Hz should be selected here.
These considerations are not relevant when measuring stationary states, or for
signals with superimposed noise.
12.3 Synchronous mode (ML801B)
If CANHEADs and an ML801B are to measure comparable responses in an
MGCplus system, a relevant filter must be selected in the ML801B, and delay
time compensation activated.
The CANHEAD filters are available in the ML801B from P6.56, and must be
activated via the software. The “Enhanced settings" dialog window of ML801B
now has “additional filter sets", where the CANHEAD filters can be activated.
This setting is permanently stored in ML801B.
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