Haltech E6M - Manual (Page 133)

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By powering up the sensor, using 12 volts (PIN B) and ground (PIN A)
the secondary trigger channel (PIN D) can be checked to identify a south pole. Connecting the
multimeter between PIN D and ground, 12 volts should be present. When a South pole is
placed in front of the sensor this value will go to 0 volts.
Fitting the magnets
We insist that only Haltech rare earth magnets (part number REM1) be used for the purpose
of triggering the sensor. Rare earth magnets purchased from your local electronics store may
be less expensive but they are not good enough! Haltech rare earth magnets are strong with
good stability to reasonably high temperatures and which have a long service life. Some rare
earth magnets are stronger but break down under excessive temperature, or are too brittle for
the purpose, or do not have a long service life. Ordinary magnets ie not rare earth types, may
not have the strength required for satisfactory triggering at high speeds.
Haltech REM1 rare earth magnets are normally 5mm dia x 2mm depth, although other sizes
are available upon special order.
The magnets should be fitted in non-ferrous surrounds such as aluminium, stainless steel or
titanium. The trigger wheel is normally made of the chosen material but various users have
reported good results when the magnets are set in a suitable non-ferrous surround and the
surround is set into a ferrous material.
The magnets should be set flush with or slightly back from the surface of the trigger wheel or
surround. If set too far back the magnetic signal may be too weak. The magnets should be set
in place with a strong and durable fixing compound such as high strength epoxy, Loctite stud
locking compound eg 603, or JBweld. Some users rely only on the fixing compound but to
ensure that the magnets remain in place but many prefer that they be retained by mechanical
means such as peening, and this gives an added safety factor.
WARNING:
RARE EARTH MAGNETS ARE EASILY DAMAGED AND THE
PEENING PROCESS (OR LOCATION BY GRUB SCREWS ETC)
SHOULD BE VERY CAREFULLY CARRIED OUT SO AS NOT TO
DAMAGE THE MAGNETS. IF DAMAGED THEY WILL NOT HAVE
SUFFICIENT MAGNETIC STRENGTH OR MAY FAIL
MAGNETICALLY OR PHYSICALLY AFTER A PERIOD OF TIME.
If installed correctly the magnets will have a long life.
Note: In the following examples, for ease of reference, the magnets are shown
mounted on the circumference of a wheel with the Haltech Hall effect sensor
oriented to one side. If so mounted the magnets need to be mounted with
sufficient strength to resist centrifugal force. In practice the magnets are often
mounted within the circumference of the wheel and the sensor is mounted so
that its base is pointed towards the magnets in the face of the wheel.