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Mean Peak to Valley Height (Rtm, Rz)

 

 

Mean peak to valley height is the difference between the highest peak and lowest valley in each sample on the evaluation length. Usually, the assessment length is divided into five sampling or cutoff lengths. Rtm is not as sensitive a single high peak or low valley measurement of the profile such as Rt, Rp or Rv.

Rtm is the mean roughness depth. Rtm is equivalent to Rz ISO when more than one sample length is evaluated (typically five). Rtm is equal to the sum of the Rp + Rv values in each sample length divided by the number of sample lengths.
Rz = Rtm = Rpm + Rvm

The current ASME/ISO Rz or maximum roughness depth parameter should not be confused with the JIS 10-point Rz or the older, defunct ISO 10-point height Rz parameter.

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