SICK MPB10 - Page 13

•
Block length
•
Alarm axis (see "Vibration monitoring", page 31)
•
Signal axis
•
Activity detection (see "Activity detection (Index 4479-4480)", page 16)
•
Trigger (see "Trigger (Index 4474-4475)", page 15)
•
Evaluation zone (see "Limit values based on ISO 10816 (Index 4534-4536)",
page 33)
Other adjustments:
•
Single-axis mode with a block length of 1,280ms
•
Number of blocks for averaging
•
Signal type
NOTICE
Changes in the vibration settings result in all set limit values and alarms being deleted.
Block length (Index 4477, Subindex 2)
The block length represents a compromise between the update rate of the characteris‐
tic values and the noise of these values. A shorter block length means more frequent
updating, a longer block length means higher averaging and thus lower noise of the
indication values. The block length can be set between 20 and 1,280ms, whereby the
maximum duration can only be used in single-axis mode.
Table 2: Block length, processing time and total block length
Block length [ms] Typical processing time [ms] Average total block length
[ms]
1,280
Only single axis possible
240 1,520
640 320 960
320 160 380
160 80 240
80 40 120
40 20 60
20 10 30
NOTE
Single-axis operation reduces the processing time to approx. 20% of the block length.
Number of blocks for averaging (Index 4477, Subindex 4)
By averaging over several blocks, the noise of the indication values can be reduced
even further. However, this reduces the update rate of the frequency and time range
parameters.
Table 3: Example values for calculating the update rate
Block length [ms] Total block length [ms] Number of blocks for averag‐
ing
640 960 3
960ms (block length) x 3 (number of blocks) = 2,880ms (update rate)
As shown in the example calculation, the value is updated only after the defined
number of recorded blocks with the corresponding processing time. This means that
this value is updated every 2.9seconds. It should also be noted that averaging is only
useful if the vibration signal also remains uniform throughout the entire averaging time.
PRODUCT DESCRIPTION 4
8028041/2022-08-16 | SICK O P E R A T I N G I N S T R U C T I O N S | MPB10
13
Subject to change without notice