Digital Aqb Diagnostics; Sine/Cosine And Hiperface Diagnostics - Allen-Bradley PowerFlex 755 User Manual
Integrated safety functions option module
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Dual Encoder Velocity and/or Position Discrepancy
The dual encoder velocity and position discrepancy diagnostic helps ensure
that the position and/or velocity of the two encoders match within a
configurable tolerance. The position and velocity discrepancy limits are
individually configurable; setting the limit to a value of 0 disables the
diagnostic check. If the module detects that the difference between the
position and/or velocity of both encoders is outside the configured limit, a
discrepancy error is reported in both safety feedback instances and the module
enters the safe state. This diagnostic is only available when the module is
configured in a dual feedback configuration.
Digital AqB Diagnostics
The following diagnostic functions are implemented in the module to perform
diagnostics for digital AqB encoders:
• Inverse Signal Monitoring
• Quadrature Error Detection
Inverse Signal Monitoring
The inverse signal monitoring diagnostic helps ensure that the inverted and
non-inverted signals are always at opposite signal levels. If the module detects a
non-inverted signal, a feedback signal lost fault is reported in the safety
feedback instance and the module enters the safe state. This diagnostic is
meant to detect encoder wiring errors, such as open, short, or short to power.
Quadrature Error Detection
The quadrature error detection helps ensure that the A and B signals from the
digital AqB encoder do not change simultaneously. This diagnostic is also
referred to as an exclusive bit check. If the module detects a quadrature error,
the safety feedback instance reports a quadrature error fault and enters the safe
state. A simultaneous change indicates an error with the encoder wiring or an
issue with the encoder itself.
Sine/Cosine and Hiperface Diagnostics
The following diagnostic functions are implemented in the module to perform
diagnostics on Hiperface and or Sine/Cosine type encoders:
2
2
• Sin
+ Cos
Vector Length Monitoring
• Zero-crossing Detection
• Signal Offset (Sine/Cosine Encoder Type Only)
Rockwell Automation Publication 750-UM005A-EN-P - October 2018
About Safe Stop and Safe Monitor Functions
Chapter 1
27
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