OHWG Series
OHWG
Wiegand sensor
Magnetic Circuit Design
The right and reasonable magnetic circuit design is very important for the operation of
wiegand sensor.
1) Dual magnetic poles ( N, S ) should trigger Alternately. The distance between poles
should be close to or larger than the length of the sensor. For example, ferrite toroidal
magnetic ring ( φ9.5 mm ) can be used in water meter, it also can apply a pair of alnico.
The distance between the two poles should be not less than 9mm.
2) When installing magnet, make sure the direction of the magnetic line parallel to the
sensor wire( refer to the triggering mode and the installlation method )
3) The triggering magnetic flux density in the position of the Sensitive wire should between
the min and max value in the characteristic list. In some application, such as calorimeter,
the magnetic intensity should be the best value. Since the magnetic intensity will reduce
with the increase of ambient temperature and the longer distance between the magnet
and sensor.
4) Magnetic shielding is necessary to prevent ambient stray magnetic field interference.
But the distance between shielding cover and magnetic ring or sensitive wire should be
not less than 10mm, and no other magnetic materials, such as iron screw.
Electric Circuit Designing
In order to avoid some possible intreference and assure the accuracy of counting, some
suggestions is offered as follows:
1)The output signal of Wiegand sensor should be shaped by wave shaping circuit first,
and then input into the two tnterfaces Io1 and Io2 of single-chip microcomputer. After
signal haping and amplification, there is a low output voltage similar to a rectangle on the
output side Vo1 (note: it is not a negative pulse), and a high output voltage similar to a
rectangle on the output side Vo2. Amplitude of the square wave is equal to supply
voltage, and the width is 20 to 30μS.
2 When designing the software, make sure that counter plus "1" after collecting both low
and high output voltage.
That is meaning, the signal-chip microcomputer I 01 only need
to collect the first low output voltage and ignore others. The same as the signal-chip
microcomputer I 02 which only collect high output voltage.
3)The software can be used to recognize the output signals and interference signals, The
Pulse Width of output signals are usually fixed, however the pulse width of interference
signals are no rule.
Nanjing Ouzhuo Technology co., Ltd
Tel：86-25-52312738，86-25-83247886
Page 4
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FAX: 86-25-52312738
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E-mail: ohhall@163.com
OHHALLSENSOR [ Nanjing Ouzhuo Technology Co., Ltd. ]
