2 ma and 21 ma the safe switching status inhibiting

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Unformatted text preview: b) Area without explosion hazard Object (1) Proximity sensor (Two-wire DC sensor consisting essentially of an oscillator circuit) (2) Circuit amplifier (3) Supply voltage (4) Binary output signal (5) Fig. 15.1.2: Circuit principle of NAMUR proximity sensors © Festo Didactic GmbH & Co. KG • FP 1110 227 15. Special designs and variants of proximity sensors The following requirements are characteristics of NAMUR switches (in simplified terms): • The current-voltage characteristic curve V(I) must be within the specified range to DIN 19 234. This guarantees that there is no sparking to trigger off explosion. The characteristic curve is effected during the transition between the switching statuses "inhibiting" and "conducting". 12 1 V 9 7 V 4 0.15 0.6 7 mA 16 I Permissible range of characteristic curve V(I) (1) Fig. 15.1.3: Current voltage characteristic curve 228 © Festo Didactic GmbH & Co. KG • FP 1110 15. Special designs and variants of proximity sensors • The response r...
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