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AS-i Speed Monitor
Safety Requirements
10.
Safety Requirements
10.1
Encoder combinations and maximum achievable safety levels
Encoder combination
1 encoder per
axis
2 encoders
coupled
1.
Fault exclusion for mechanical shaft breakage required.
Warning!
The maximum achievable safety level depends on the encoder, the circuitry and the
operating mode of the speed monitor.
When using non-safety rated encoders the signal tracks must be generated inde-
pendently. The two signal tracks may not be generated by a common processor or
derived from each other by an electronic circuit.
•
For the purpose of fault exclusion signal and inverted signal have to be con-
nected.
•
The rotary encoders must have a suitable performance level for the applica-
tion.
•
Please observe the information provided by the rotary encoder manufacturer.
36
Sin/Cos
(SIL3/PLe certified)
Sin/Cos (standard)
TTL (standard)
Sin/Cos
Sin/Cos
Sin/Cos
SSI
SSI
TTL
DC
Achievable safety level
-
99%
SIL3, PLe, Cat.4
-
90%
SIL2, PLd, Cat.2
-
60%
PLc, Cat.1
Sin/
99%
SIL3, PLe, Cat.4
Cos
TTL
SSI
SSI
TTL
TTL
1
1
1
Tab. 10-14.
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