ABB Wireless Proximity Switches Planning And Installation Manuallines page 15

Planning and
Installation Guidelines
V 6 Technical Description
Wireless Proximity Switches / Issue: 09.2004
Effective switching distance s
The effective switching distance considers ambient temperatures in the range of –25 °C to
+70 °C and is further 10 % above or below the real switching distance, i.e. between 81 % and
121 % of the nominal switching distance.
Reliable switching distance s
The reliable switching distance is between 0 % and 81 % of the nominal switching distance and
is recommended for the use of the sensor head under determined conditions.
S
u ma x
S
r ma x
S
n
S
r min
S
u min
S :
reliably switched on
a
Fig. 2.1: Different switching distances
Repeat accuracy R
The repeat accuracy specifies the variation of the real switching distance over a period of eight
hours at an ambient temperature of (23 ± 5) °C.
Hysteresis H
In order to avoid bouncing of the output signals the sensor head's switching point for an
approaching actuator differs by a hysteresis from the switching point for a receding actuator. The
hysteresis is determined at an ambient temperature of (23 ± 5) °C and specified relative to the
real switching distance.
Reliably switched off
A sensor head is switched off reliably, if the distance between the active sensor face and the
measuring plate is at least three times the nominal switching distance.
Radially moved actuator
Depending on the axial distance to the active sensor face, a radial motion of the actuator results
in an other switching distance than an axial motion. This is shown in the standardized pick-up
characteristic curve for inductive proximity switches which is also valid for sensor heads.
u
a
reliably switched off
Measuring plate
S
u ma
S
r ma
S
n
S
r min
S
u min
active face of the sensor head
Sensor head
+ hysteresis
x
+ hysteresis
x
+ hysteresis
+ hysteresis
+ hysteresis
Planning and Installation Guidelines 15