How is alignment verified?
Checking that the fixture points where it should, relative to its reference axis, before any light is measured.
Photometric readings only mean something if the fixture is pointed correctly. Alignment verification checks the aim of the fixture against its reference axis before and during measurement, so that the angles in the results match the angles on the airfield.
The fixture is fixed on a test mount and levelled. The measured beam axis is then compared with the reference axis, and the angular offset between them is checked in both the horizontal and vertical planes. A fixture that is misaligned gives readings that look like a faulty beam when the real problem is the setup.
Frequently Asked Questions
Q1What is alignment verification?
Checking that a fixture is pointed correctly relative to its reference axis. It is done on the test mount so that the angles recorded in the photometric results are true.
Q2Why is alignment checked before photometry?
A fixture that is tilted or turned gives readings shifted in angle. That can look like a weak or off-centre beam when the beam is actually fine.
Q3What is the reference axis?
The direction the fixture is designed to point, defined by the manufacturer's data and the applicable standard. Measurements are taken relative to it.
Q4What is the angular offset?
The angle between the measured beam axis and the reference axis. A small offset is expected; the permitted amount is set by the standard or the manufacturer.
Q5Why check both horizontal and vertical planes?
The fixture can be off in either direction, or both. Checking the two planes separately shows which adjustment is needed.
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