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PHÖNIX Messtechnik GmbH, Salzschlirferstr. 13, D-60386 Frankfurt/M., Germany, Tel: +49/69/416742 -20, Fax: -29
13
Fig. 8: A two-step action with a PHÖNIX level switch type 740.0060 utilising its hysteresis.
4.2 Using the type 740.0065NA in a hazardous area
The limit switch type 740.0065NA is designed for usage in NAMUR-circuits (s. fig. 2b). It consists only of
passive devices (switch and resistors), which allows - according to EN 50020 / VDE 0170 part 7 - the us-
age in hazardous areas zone 1 and 2, if they are part of a intrinsic save circuit and the maximum values of
voltage, current and power are not exceeded. The maximum of self heating is determined by R
S
(R
T
=
180°C/W) and the utilised power supply. If using the type 740.1061 (P
max
=51mW), the heating up is less
than 10°C.
Fig. 9: Usage of the type 740.0065NA in a hazardous area
4.3 Heat protection in high temperature
If medium temperature is more than 150°C (>260 °C for 740.0065NA) to reduce the heat radiation a heat
protection plate (Order-No.: 5745000159) has to be mounted between the tube and the switch. In this
case the switch must not be isolated together with the tube.
5 Maintenance
The switch is free of maintenance.
6 Warranty
We grant a guarantee period of 24 months for our products, provided that they have been handled and
operated under conditions described in the Operating Manual. In case of wear and spare parts we only
guarantee for failures in construction and material.
supply
Typ 740.0065N
Typ 740.0065N
safe
area
hazardous
area