Wiederholbarkeit oder Nichtwiederholbarkeit

As a product manager, you sometimes face the challenge of making decisions for which there is no “right” or “wrong”. What sounds very philosophical at first has a very real background. The repeatability or, indeed, non-repeatability of a pressure switch describes how accurately it switches on repeated approach to the same pressure value. Which makes this information one of the most important, if not the most important, specification for pressure switches. Not least for this reason the following applies: the better the (non-)repeatability, the more expensive the switch. The real problem lies in the naming of this specification. What’s right: repeatability or non-repeatability?

Scientific definition

From a technical-mathematical point of view, the question is quickly answered: The repeatability describes the accuracy with which the switch switches with repeated approach to the same pressure value, while the non-repeatability is the opposite and therefore describes with what inaccuracy the switch switches with repeated approach to a pressure value.

In a concrete example, this would look as follows: If the repeatability is 99 %, the non-repeatability is 1 %. In other words: The actual switching point may be up to 1 % different from switching event to switching event. Sounds logical, right? So what’s the problem?

Global approach

In some target markets, and actually in the “British standard” for pressure switches, it is common to refer to non-repeatability as repeatability. Confused? What is meant is that the term “repeatability” means non-repeatability from a technical-mathematical point of view. Accordingly, the pressure switch of the above example would have a repeatability of 1 %.

It is therefore complicated when one serves, as a company (such as WIKA), the most diverse target markets with various switches. The challenge for product management is to want to speak the language of the customer for the individual switch and, accordingly, to have to choose between repeatability and non-repeatability. But what about the philosophy of the portfolio and your own sales department? How do I explain to them that I mean the same thing with two terms that mean the opposite? That would almost be like saying “day” for day, but then, some of the time, saying “night” for day.


Since there is no “right” or “wrong” as already written, you will also find both terms with WIKA. And basically, it does not matter whether the term repeatability or non-repeatability is used in a data sheet, because, if the value is small, one can be sure that non-repeatability is always meant from a technical-mathematical point of view. Since a switch with a 99 % error would hardly be useful.

For more information on our range of pressure switches, visit the WIKA website.

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