SI25101B_e.DOC / Mrz-08
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7.
Delays
There is a delay time between the analogue input signals and the incremental output signals,
which is typically 3
μ
sec. when the divider is switched off.
Use of the divider function will extend the delay time correspondingly.
Since the delay time is constant, there will be a phase displacement between input and output,
depending on the actual frequency.
8.
Miscellaneous Hints
•
The unit will reach full accuracy only after a transient period of approximately 20 full
sine cycles at the input. Before that, the input frequency should not exceed about 50 %
of the normal maximum frequency
•
The application of digital interpolation procedures requires use of quantization steps,
which can cause a certain dither of the output signal.
•
The quality of the output signal depends essentially on the input signals. Therefore
maximum elaborateness is recommended with screening, running of cables and cable
length.
•
SI251 does not possess a potential separation, i.e. the unit GND is at the same time
also GND of the sensor. Therefore it is important to ensure clear conditions with
earthing and to prevent earth loops and balance currents flowing through the unit.
Where unrulable potential situations should come up, it is recommended to use a fully
separate power supply for the SI 251 unit
