English to Portuguese Tech/Engineering Electronics / Elect Eng método de ensaio

Bracketing by Handwheel Procedure
If the handwheel reading for the sample is bracketed by those of the reference fuel blends calculate the cetane number, in accordance with Eq 4, from the handwheel readings of the sample and each of the bracketing reference fuels and continue the test; otherwise try an additional reference fuel blend(s) until this requirement is satisfied.

They are installed in a bracket positioned over the flywheel so that they clear the flywheel indicator which triggers them.
(bracket positioned)

Select another reference fuel blend which can be expected to result in a handwheel reading that causes the two reference fuel handwheel readings to bracket that for the sample. (readings to bracket)

The actual compression ratio is not important but an indication of compression ratio which relates to cetane number is a useful guide for selecting reference fuels to bracket the sample of diesel fuel oil. ( to bracket the sample)