Quantum mechanics was developed with the aim of describing atoms and to explain the observed spectral lines in a measurement apparatus.

Thus, the non-physical mind is postulated to be the only true measurement apparatus.

Lead absorbers can be placed around the measurement apparatus to reduce background radiation.

In quantum mechanics, "observation" is synonymous with quantum measurement and "observer" with a measurement apparatus and observable with what can be measured.

Thus, we can probe the measurement apparatus with a statistical mixture:

Maintenance staff could also use it as a measurement apparatus, to check for losses in transmissions and level alignment, provided that they used exclusively sine waves as test signals.

The islands host a variety of measurement apparatus for space launches.

It is caused by inherently unpredictable fluctuations in the readings of a measurement apparatus or in the experimenter's interpretation of the instrumental reading.

A further aspect of a frame of reference is the role of the measurement apparatus (for example, clocks and rods) attached to the frame (see Norton quote above).

The reference measurement is typically defined by the local laboratories or dependent on individual measurement apparatus.