ABL/AKL-Series Gear-Tooth Sensors
Block Diagrams
Features
•
Wide airgap
•
Analog and digital versions
•
Large analog peak-to-peak signal
•
Single- and dual-bridge versions
•
Operating frequency to 1 MHz
•
150°C operating temperature
•
Packages as small as 2.5 mm x 2.5 mm
ABL00x
V
CC
Voltage
Regulator
3.3V
ABL01x
Applications
•
Motion, speed, and position sensing
•
Linear and rotational encoders
•
Closed-loop servo systems
•
Automotive sensors
Switching
Current
Source
GMR
Bridge
A
Offset
Detector
Description
ABL and AKL-Series Gear-Tooth Sensors are versatile,
wide airgap sensors typically used with ferromagnetic gears
and bias magnets.
Three standard spacings are available for use with gear
pitches as small as 0.6 mm, to 6 mm or more.
EEPROM
Gain
A
Current Level
AKL00x
Outputs
GND
ABL-Series analog sensors have differential sensor elements
that provide sinusoidal outputs. Single- or dual-bridge
configurations are available. Dual-bridge versions provide
sine and cosine outputs for direction information.
AKL-Series sensors combine a sensor bridge with integrated
signal processing to provide a 50% duty cycle digital output.
Integrated signal processing includes gain and offset
normalization. AKL-Series sensors are configured as two-
wire devices, where the supply current indicates passing
teeth.
V
Gear
Rotation
V
Gear
Rotation
ABL00x
Single-bridge analog sensor
ABL01x
Duak-bridge analog sensor
mA
8
4
Gear Rotation
AKL00x digital gear-tooth sensor
1
NVE Corporation
11409 Valley View Road, Eden Prairie, MN 55344-3617
Phone: (952) 829-9217
Fax: (952) 829-9189
www.nve.com
©NVE Corporation
Absolute Maximum Ratings
ABL-Series Analog Gear-Tooth Sensors
Parameter
Min.
Max.
Supply voltage
30
Storage temperature
−65
170
ESD (Human Body Model)
400
Applied magnetic field
Unlimited
AKL-Series Digital Gear-Tooth Sensors
Parameter
Min.
Max.
Supply voltage
−60
45
Continuous output current
16
Junction temperature
−40
170
Storage temperature
−65
170
Junction temperature
−40
170
ESD (Human Body Model)
2000
Applied magnetic field
Unlimited
Units
Volts
°C
Volts
Oe
Units
Volts
mA
°C
°C
°C
Volts
Oe
Operating Specifications
Parameter
Operating temperature
Supply voltage
Resistance
Offset voltage
Non-linearity
Hysteresis
Saturation of GMR sensor elements
Single resistor sensitivity
Maximum output
Resistance temperature coefficient
Operating frequency
ABL-Series Analog Gear-Tooth Sensors
Symbol
Min.
Typ.
T
min
; T
max
−50
V
CC
0
4
5
V
O
−4
Max.
150
30
7
+4
2
2
+180
0.04
80
+0.11
1
Units
°C
V
kΩ
mV/V
%
%
Oe
%/Oe
mV/V
%/°C
MHz
Test Condition
At 25°C
Unipolar field
sweep across near
operating range
−180
∆R/Oe
TCR
f
MAX
0
No applied field
AKL-Series Digital Gear-Tooth Sensors
(T
min
to T
max
; 4.5 V < V
CC
< 36 V unless otherwise stated)
Parameter
Symbol
Min.
Typ.
Max.
Units
Test Condition
Operating temperature
T
min
; T
max
−40
150
°C
Supply voltage
V
CC
4.5
36
V
Off-state supply current
I
OFF
3.4
4
4.8
mA
V
CC
= 12V
On-state supply current
I
ON
7
8
9
Output duty cycle
40
50
60
%
Airgap
AKL001-12
1
3.5
AKL002-12
1
2.5
mm
AKL003-12
1
2
Operating frequency
f
MAX
DC
10
kHz
2
NVE Corporation
11409 Valley View Road, Eden Prairie, MN 55344-3617
Phone: (952) 829-9217
Fax: (952) 829-9189
www.nve.com
©NVE Corporation
Operation
Biasing
To detect gear teeth, a permanent magnet is required to generate a magnetic bias field. The sensor can then detect magnetic field
variations as the gear tooth passes by.
Here are some tips for biasing:
•
Because of GT Sensors’ high sensitivity, small, inexpensive Ceramic 8 ferrite magnets can be used
for most applications. Small sensors and magnets allow small circuit boards.
•
Alnico 8 magnets can be used in high temperature applications.
•
Rare-earth magnets are not recommended because they tend to saturate the sensors.
•
Magnets and sensors can be placed on opposite sides of a 1.5 mm thick (0.062 inch) circuit board,
which provides a convenient spacing for many applications (see Figure 1).
•
The magnet can be glued to the circuit board using high-temperature epoxy adhesive.
•
For more precise positioning, a pocket to hold the magnet can be machined into a thicker circuit board.
•
If zero speed operation is not required, AC coupling the sensor removes the electrical offset induced by magnetic
imperfections.
•
If zero speed operation is required, zeroing the sensor output offset maximizes airgap (AKL-Series sensors have integrated
zeroing).
Sensor orientation
To align with the axis of sensitivity, sensors should be oriented with the gear teeth perpendicular to the length of the sensor as
shown in Figure 2:
ABL00X-10E
AKL00X-12E
PCB
Magnet
Figure 1. Biasing
magnet.
Figure 2. Sensor orientation.
Recommended sensor element spacing vs. gear pitch
Optimal sensor element spacing depends on a number of factors, including gear pitch, magnet, and sensor spacing. A rule of thumb
is to select a sensor with an element spacing of approximately one-fourth the gear pitch. For example, for a gear pitch of 1 mm, the
optimal element spacing would be 0.25 mm. Therefore a sensor with s 0.3 mm spacing, the closest available, would be selected.
3
NVE Corporation
11409 Valley View Road, Eden Prairie, MN 55344-3617
Phone: (952) 829-9217
Fax: (952) 829-9189
www.nve.com
©NVE Corporation
Sinusoidal output with rotation
As shown in Figure 3 below, a biasing magnet provides a field, and the magnetic flux lines are deflected into the direction of
sensitivity by passing metal gear teeth. Sensors are placed between the magnet and gear teeth. Thus the sensor produces a
sinusoidal output with one cycle per tooth.
Dual-bridge sensors provide a second bridge output out-of-phase with the first sensor.
Magnet
Bridge
Figure 3. ABL00x output vs. gear rotation.
4
NVE Corporation
11409 Valley View Road, Eden Prairie, MN 55344-3617
Phone: (952) 829-9217
Fax: (952) 829-9189
www.nve.com
©NVE Corporation
u
u
u
u
u
Typical outputs
Figures 4 to 6 show typical outputs from each of the three GT Sensor types:
0.3
0.2
Output (V)
0.1
0
-0.1
-0.2
-0.3
0
Figure 4. ABL00x output (per tooth + gap)
0.3
0.2
Output (V)
0.1
0
-0.1
-0.2
-0.3
0
Figure 5. ABL01x output (per tooth + gap)
8
Output (mA)
6
4
2
0
0
Figure 6. AKL00x output (one pulse/tooth)
5
NVE Corporation
11409 Valley View Road, Eden Prairie, MN 55344-3617
Phone: (952) 829-9217
Fax: (952) 829-9189
www.nve.com
©NVE Corporation
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