TDR9000
™
Circuit Breaker Test System User’s Guide
72A-1898 Rev. A 11/01 A-61
Monday, November 26, 2001 1:09 pm
When The rotary to linear Transfer Function is used with Metric
transducer units, the default value is 1 cm/1 deg., which results in a ratio
below the limit imposed by the Instrument.
5" = 2.54 x 5 = 12.7cm
1 deg./360 deg. x 12.7 cm = 0.0353 cm
1 cm/0.0353 cm = 28.35
The following example underlines the importance of the transducer
resolution when the rotary to linear Transfer Function is used.
Example: In the SFA Circuit Breaker, when the Main Contacts travel
8.05", the rotation at the rotary input of the transducer is 35.5 deg
(Figure A.73).
Figure A.73 Rotary-To-Linear Transfer Function
This corresponds to a linear travel at the transducer end of:
35.5 deg./360 deg. x 5" = 0.493"
.
This results in a primary motion (Circuit Breaker Main Contacts) to
secondary motion (transducer) ratio of:
8.05"/0.493" = 16.32.
In primary terms the resolution of the measurement becomes:
0.00125" x 16.32 = 0.0204".
This resolution is sufficient for SFA published tolerances (for example,
wipe 1.06
±
0.06), however, transducer resolutions worse than 0.00125,
that are used with a Transfer Function, should be considered
questionable in applications such as these.
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