Diodes ZMT32 - Manual (Page 5)

ZMT32
Issue 1 - June 2008 5 www.zetex.com
© Zetex Semiconductors plc 2008
Operating principle
When a common-magnetic field is applied through the
ZMT32 the 2 internal magneto-resistive bridges are
affected slightly differently due to their 45° rotation to
one another. This 45° rotation enables the ZMT32 to
determine angular position, of a rotating magnetic
field.
When a rotating magnetic field is applied to the ZMT32
it will output 2 sinusoidal voltages that are:
• proportional to the field strength applied
• proportional to the supply voltage applied,
• rotating at twice the angular position
• 90° apart (as seen below).
By taking the arcTan of the ratio of V
O2
to V
O1
the
angular position of the magnetic field can be
determined.
Characteristic output curves V
O1
, V
O2
H
rot
1
␣
0
O
GND1
8 GND2
7
+V
O2
6
+V O1
5
1
-V
O1
2
-V
O2
3
V
CC2
4
V
CC1
α = 0°
Bridge
1
Bridge
2
-V
O1
-V
O2
V
cc1
V
cc2
GND1
GND2
+V
O1
+V
O2
1
-15
-10
-5
0
5
10
0 45 90 135 180 225 270 315 360
O
u
tp
u
t vo
lt
ag
e (
m
V
/V
)
Cos 2 α
Sin 2 α
Sensor bridge 2
Sensor bridge 1