Operation; Typical Performance - Siemens Sitrans WM100 Operating Instructions Manual

Operation

When power is initially applied to the WM100, the alarm relay is energized and held
artificially by the timing circuit. This will simulate the normal operation of the WM100 for
a start up delay of >10 seconds (or >5 seconds if a jumper is wired across terminals 7 and
8).
As a ferromagnetic object passes through the probe's permanent magnet field, the
distortion of the flux is sensed by the magnetic detection circuit. If the distortion is of
suitable magnitude, a short pulse is generated to reset the timing circuit, visible to the
user by the LED shown in the lid window. This action keeps the alarm relay energized
providing fail-safe operation of the contacts.
If no change in flux (target motion) is sensed for a period of 10 seconds (or 5 seconds if a
jumper is wired across terminals 7 and 8), the timing circuit will not be reset. This will
cause the alarm relay to de-energize and the contacts to change state.
Thus the WM100 cannot detect the motion of uniform ferromagnetic masses such as a
rotating pulley or a keyless shaft.
When adjusting the WM100 mounting position, it may take up to 10 seconds for the
detection circuit to adjust to the new ambient magnetic environment. During this
adjustment period, the LED may fail to flash for an otherwise normally detectable moving
target.

Typical Performance

The maximum air gap for which the WM100 will reliably detect the moving ferrous target
varies according to the target's size, shape, orientation and direction of motion, as well
as the material to which the target is attached.
An example shown below compares typical results from steel blocks used as targets on a
wheel (either ferrous or non-ferrous). As shown, a larger detection range can typically be
achieved when there is a ferrous object behind the target. The WM100 provides excellent
detection of a relatively small target, such as a 3/16" (~5 mm) shaft key installed in a 5/8"
(~16 mm) motor shaft with < 0. 1 25" (~3 mm) of the key protruding beyond the shaft
envelope.
To ensure proper operation in any setup, use the LED indicator to confirm consistent
detection of the target over the full range of expected operational speeds. Note that
detection range may vary slightly with voltage supply and temperature, so it is
recommended to use the minimum air gap that is physically safe to implement.
Page 8 SITRANS WM100 – OPERATING INSTRUCTIONS 7ML19985MW01