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The PRofile no. 22 - 5941 The Three Methods

1 “Endpoint to endpoint”calculation of the temperature coefficient2 “Box method”based on min./max. values for temperature and mA signal.3 The industrial standardIEC 68-2-2 based on four point measure- ments using the poorest value. Point to pointBox methodThe industrial standardIEC 68-2-2

mA Temp. mA Temp. mA Temp.

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25° -40° 85° 25° -40° 85° 25° -40° 85°

Figure 1Figure 2Figure 3 Critical Values Can Be “Improved” by a Factor of 8 The importance of Safety The example illustrates how the temperature coeffi- cient data can be “improved” from two to three times solely be using a “home-made” definition rather than using the European standard IEC 68-2-2. If these unreliable methods are combined with the use of typical values (e.g. average values) rather than the extreme min./max. values, then “improvements” of up to eight times are possible. Customers Burdened with Unfair Responsibility Product specifications are more than just numbers on a piece of paper. In terms of the day-to-day operation, differences in measurement methods will be reflected in differences in accuracy, operational reliability, and life cycle. It is therefore always very important to ob- tain the legitimacy of a documented and recognised method. The applied measurement methods are seldom stated in product data sheets and it is thus up to the client to ask about them. The temperature coefficient has been used here as an example, but one could also question definitions and measurement methods con- cerning the reliability and stability of the results for other data. Many manufacturers state typical values instead of min./max. values and these typical values may be based on very few measurements.

The mission of PR electronics is to be a technological leader in signal conditioning. A very demonstrable result of this policy is that we always state min. or max. values and use recognised, unambiguous indu- strial standards such as IEC 68-2-2 as the basis of our product specifications. This means that anyone can verify our product data independently.