Rion VM-83, Instruction Manual, Page: 86 / 106

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Technical Information
Display range
This section provides information on the numeric range of the digital display
used in the VM-83.
For simplifi cation, the range is assumed to be “100” and “30”, and the display
characteristics setting EQ PEAK. Because the overload point of this unit is
approximately three times the range full-scale point, the display range at
the range “100” setting is about 300, and at the “30” setting (actually 31.6)
is about 90, assuming that there is no overload in the intermediate circuits.
The display resolution is 0.1 and 0.01. Therefore the possible display range
is as follows:
Range Display range
100 0.1 to 300.0
30 0.01 to 90.00
The VM-83 directly feeds the raw waveform of the vibration signal to an
A/D converter and then performs fi lter processing, rms conversion, and
other functions using a DSP. When the number of effective digits for display
decreases, display accuracy cannot be maintained. Therefore the indication
UNDER appears on the display when the displayed value falls below 0.5%
of the full-scale point. This warns the user that the current range setting is
not appropriate. To assure accurate readings, the range setting should be
made so that the UNDER indication does not appear. At a level of 0.2% of
the full-scale point and lower, the lowest bit level of the A/D converter is
reached, so that readings will be indeterminate. At a range “30” setting, this
corresponds to 0.06 and at a range “100” setting, this corresponds to 0.2. This
means that readings below this limit will be highly imprecise, and that the
display reading may not be 0 even if the actual vibration signal is very low.