Plain-language explanations of the measurements, sensors and numbers behind environmental monitoring.
Percent of full scale fixes an error band in absolute units across the whole span while percent of reading scales it with the display, and the difference decides whether a low reading means anything at all.
Read Article→A voltage range describes what an instrument will read, a measurement category describes where it may be connected, and a listing that gives one without the other leaves the safety question unanswered.
Read Article→A meter fuse protects the current input path and its interrupting capacity has to match the fault energy the category implies, but the category itself comes from clearances and input protection rather than from the fuse.
Read Article→Exceeding a measurement category usually ends in a flashover across internal clearances rather than a blown display, and the most common outcome is an instrument that still reads correctly with its safety margin gone.
Read Article→The line between CAT III and CAT IV is the origin of the installation at the main overcurrent device, and the voltage printed beside the category does not move that line.
Read Article→A voltage rating describes the steady voltage an instrument can read, while the measurement category describes the transient energy it can survive at a given point in the installation.
Read Article→A category rating describes the energy of the voltage spike your position in the installation can deliver, not the voltage you expect to read.
Read Article→No. The ratio is a geometry figure with no bearing on accuracy, and a tighter cone is harder to aim and easier to miss with.
Read Article→A projected circle draws the area being averaged, while a single dot only marks roughly where the centre of it is.
Read Article→The terminal occupies a small fraction of the measured circle, so its heat is averaged away by the cooler metal around it.
Read Article→Multiply the ratio by one inch for the absolute limit, then divide by three for a distance that gives a reading worth keeping.
Read Article→The ratio fixes how wide a circle the instrument averages, and a target smaller than that circle is never measured properly.
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