4
Safety requirements
Encoder requirements
Manual – MOVISAFE
®
CS..A Safety Card
32
4.6.4
Quantization error
Position
The actual position value is formed directly from the encoder increments. On the basis
of one encoder revolution, this results in the following quantization error for the actual
position value, which is included in all position functions:
•
EI7C FS: 3.75 °
•
AK0H: 0.8 °
•
AK1H: 0.09 °
•
E..7S: 0.09 °
•
A..7W: 0.05 °
Speed
The speed calculation determines the average speed in the time range set via the
Fil-
ter time speed SinCos (8708.3)
parameter:
Quantization error_v in 1/min =
(15 s x 1/min) / (PPR_count x parameterized_filter time)
In addition to the process-related quantization error, there is an additional actual
speed error of 0.3%:
Error_v_SinCos = Actual speed x 0.3% + Quantization error_v
The speed calculation for the encoder EI7C FS determines the average speed over
the last 4 recorded encoder increments. The response time of the encoder evaluation
is thus dependent on the actual speed. The error in the calculated speed value equals
a maximum of 1% of the actual speed:
Error_v_EI7C FS = Actual speed x 1%
Setting the
Filter time speed HTL (8708.4)
parameter makes it possible to filter the cal-
culated speed via a sliding average value filter with the parameterized length.
Acceleration
The acceleration calculation determines the average acceleration in the time range set
via the parameter
Filter time acceleration (8708.2)
. The quantization error that thereby
occurs decreases as the filter time increases. In return, the response time increases in
accordance with the filter time.
Quantization error_a in 1/min s =
(120 s x 1/min) / (PPR_count x (parameterized_filter time)
2
)
In addition to the process-related quantization error, there is an additional actual ac-
celeration error of 0.5%:
Error_a_SinCos = Actual acceleration x 0.5% + Quantization error_a
24842532/EN – 04/2018
