The meters in this category all answer the same question - how much water is in the paper - but they differ in where they take the reading. That is what the choice turns on: a stack in the warehouse, a running reel, a single sheet in the laboratory, a bale of recovered paper or the web on the machine.
A sword probe is pushed between the sheets of a stack, so the measurement happens inside the pallet rather than on its surface, where the paper has already exchanged moisture with the room. The RH5, the RH5.1 and the RH6 all work this way.
The PM5 measures on the reel without stopping the machine. The PMP, the direct successor to the P2, measures the absolute water content of paper and solid board. The PMSA is a laboratory analyser for a single sheet, and its applicability is set by three figures: grammage, thickness and the smallest sheet format it can take.
A bale of recovered paper is bought by weight, and the water in it is paid for at the price of the paper. The RP6 measures inside the bale without taking it apart, which is what makes a moisture check possible at intake rather than after the bale has been opened.
The MF-P-HTD is mounted above the web and measures without contact, in real time, while production runs. The reading is independent of web speed and goes to the control room over the chosen interface, so it serves both to document quality and to control humidification or drying. The basis weight of the material decides between it and the MF-S-HTD, its sister sensor for solid board and panels.
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