Wika S-20 Manual do Utilizador descarregar pdf (Página 10)

WIKA Safety manual pressure transmitter, model S-20

14082128.02 06/2014 GB/D/F/E

WARNING!

The model S-20 is only suitable for pressure measurement in applications where the pressure values

change dynamically. The external supervisory logic unit must bring the plant to a safe condition if a low

alarm value occurs.

The user is obliged to design the entire safety function in accordance with EN ISO 13849-1:2008. The safety function

can, at most, achieve the PL of the model S-20. The external logic unit must, at the very least, full the same require-

ments with respect to EN ISO 13849-1:2008 as the model S-20.

Accuracy of the safe measuring function

The total safety accuracy is ±(2 % + 0.3 % drift/year).

The maximum measuring deviation, in addition to the accuracies stated in the data sheet, includes the following errors:

■

EMC

■

Temperature error

■

Long-term stability

2.6 Test to discover a signal drift

A check of the pressure transmitter for any possible drift behaviour must be carried out through the external logic

unit after powering up in the unpressurised state. It must be assumed that there are no errors in the instrument if the

following condition applies:

■

Zero oset less than 0.2 % of the nominal pressure

This test can be carried out either:

■

at each commissioning of the application in the unpressurised state

■

or in a time interval of a maximum of 12 months with the maintenance of the application.

2. Safety

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Wika S-20 Manual do Utilizador Página 10