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===Optical counting methods=== ...electron microscope|electron micrographs]] is now commercially available. Instruments such as the Retsch Camsizer can perform this analysis on the run using stan

The early work involved measuring dust exposure by counting the number of particles collected from the air by sampling devices. A subst ...pointed IOM as its central reference laboratory for man-made mineral fibre counting.

...e:Hf2li aufsicht bg blue.png|thumb|250px|A PC-controlled model from Zurich Instruments.]] ...tal lock-in amplifier with PPM resolution | journal = Review of Scientific Instruments | volume = 65 | issue = 3 | pages = 747 | publisher = AIP | month= March |

...by measuring the time required for an entire number of cycles, rather than counting the number of entire cycles observed for a pre-set duration (often referred ...More complex signals may need some conditioning to make them suitable for counting. Most general purpose frequency counters will include some form of [[electr

*Convenient counting of optical frequencies using [[Frequency comb|optical combs]]. ...ium gas standards have seen use in telecommunications systems and portable instruments.