1121 Transducer damping ratio
Posted: Fri Jun 26, 2009 9:35 am
At the TaskForce meeting in Aachen we discussed an old request from Brian Grenke
to introduce a new descriptor "Transducer damping ratio".
The decision was :
-> "Please use the descriptors 'Transducer type' and 'Transducer id' (new in MME 1.5)
instead of 'Transducer damping ratio'."
Brian Grenke answered to this decision:
Good morning,
The 'Transducer damping ratio' is a separate descriptor of the transducer.
It is tied to the 'Transducer natural frequence' to define the amount of damping, as exhibited in the transducer frequency response.
This is important when considering the 'total response corridors' defined in SAE J211 and ISO 6487. The 'total response corridors" include the overall frequency response of the entire data collection system, and includes:
1) transducer damping (as defined by the 'transducer natural frequency' and 'transducer damping ratio')
2) data acquisition system anti-aliasing filter (defined by the filter frequency and the number of poles, and possibly nodes)
3) post-test filtering.
The last step is user controlled and should be designed to add the proper amount of additional signal attenuation to bring the first two into the CFC filter corridor.
Even so-called 'undamped' accelerometers will have a 'transducer natural frequency' and 'transducer damping ratio' although these are generally in a range which makes the transducer attenuation insignificant compared to the DAS anti-aliasing filter attenuation.
This is why I requested the 'transducer natural frequency' and 'transducer damping ratio' be added to the channel information header.
Brian Grenke
CHRYSLER - Chelsea proving grounds
Data Analysis Specialist
734-475-5428
Life is a ball, learn to bounce.
We should discuss his answer at the next meeting!
to introduce a new descriptor "Transducer damping ratio".
The decision was :
-> "Please use the descriptors 'Transducer type' and 'Transducer id' (new in MME 1.5)
instead of 'Transducer damping ratio'."
Brian Grenke answered to this decision:
Good morning,
The 'Transducer damping ratio' is a separate descriptor of the transducer.
It is tied to the 'Transducer natural frequence' to define the amount of damping, as exhibited in the transducer frequency response.
This is important when considering the 'total response corridors' defined in SAE J211 and ISO 6487. The 'total response corridors" include the overall frequency response of the entire data collection system, and includes:
1) transducer damping (as defined by the 'transducer natural frequency' and 'transducer damping ratio')
2) data acquisition system anti-aliasing filter (defined by the filter frequency and the number of poles, and possibly nodes)
3) post-test filtering.
The last step is user controlled and should be designed to add the proper amount of additional signal attenuation to bring the first two into the CFC filter corridor.
Even so-called 'undamped' accelerometers will have a 'transducer natural frequency' and 'transducer damping ratio' although these are generally in a range which makes the transducer attenuation insignificant compared to the DAS anti-aliasing filter attenuation.
This is why I requested the 'transducer natural frequency' and 'transducer damping ratio' be added to the channel information header.
Brian Grenke
CHRYSLER - Chelsea proving grounds
Data Analysis Specialist
734-475-5428
Life is a ball, learn to bounce.
We should discuss his answer at the next meeting!