Originally shared on the public FactorioPrints / Factorio School archive (factorioprints.com · factorio.school). Authorship preserved from the public catalog.
Simple compression tester for belts.
Can detect any gaps in the belts, even the smaller ones.
Green light = compressed belt. Red light = uncompressed belt.
Curved sensors are more accurate than linear or single ones (they don't detect small gaps).