1121 Transducer damping ratio

[derpmann]

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!

[DiVe]

For the version 1.6 there will be two optional descriptor added for each channel:
WITHDRAWN: see below!
".Transducer natural frequency"; float, unit [Hz]
".Transducer damping ratio";float, unit [1]

[KevinEgle]

Hello,

sorry to bring this old discussion but
".Transducer natural frequency" has 30 characters and is therefore to long.

The standard states here "Each line, except “Value of samples”, shall begin with a description field having a maximum of 28 characters.
Position 29 may be a colon."

I would recommend ".Transducer natural freq." as new field name

Kevin Egle
Humanetics Europe GmbH

[derpmann]

Hello,

the members of the MME-TaskForce agreed to use

Transducer natural frequency and
Transducer damping ratio

without the leading dot, to avoid the violation of the 28 character rule.

Peter

[KevinEgle]

Hello,

thank you for the fast clarification.

Kevin Egle
Humanetics Europe GmbH