AA700 family AMR FreePitch sensors for angle and length measurement
General information
The sensors in the AA700 family are FreePitch sensors based on the anisotropic MagnetoResistive (AMR) effect.
The sensors offer
- Extremely low harmonic output signals and non-contacting measurement
- A large working distance
- Excellent accuracy even with low field strengths
- Large tolerance of axial offset
Product variants
This product family has three sensor variants for you to choose from.
- AA745 FreePitch sensor for measuring at the shaft circumference.
- AA746 FreePitch sensor for use with low field strengths.
- AA747 Free pitch sensor for angle measurement at the shaft end.
Design features
FreePitch sensors can be used independently of a magnetic pole pitch – e.g. with a dipolar magnet at the shaft end.
The design of the sensors is based on PerfectWave technology, which improves signal quality by suppressing the harmonics.
Application examples
Suitable for absolute or incremental applications (linear or rotary motion) e.g.:
- Motor commutation
- Speed measurement
- 180° absolute angle detection at the shaft end
General information
The sensors in the AA700 family are FreePitch sensors based on the anisotropic MagnetoResistive (AMR) effect.
The sensors consist of two Wheatstone measuring bridges at an angle of 45° to each other. A rotating magnetic field (e.g. a dipolar magnet) at the sensor level supplies two signals with a phase shift of 90° relative to each other (sine and cosine) with double the frequency of the magnetic field.
All sensors from the AA700 family feature PerfectWave technology and provide extremely low harmonic output signals.
The sensors are available in various processing variants. As bare-die, the sensors can be fitted directly using chip-on-board technology. The SO8 housing is suitable for applications at the shaft end and can be easily fitted on a PCB. The special SIL6 and LGA6 package allows SMD assembly, but can be fitted to a PCB edge - this enables small distances between the sensor and the measurement scale in the application.
Product variants
| Name | Housing | Amplitude | Offset | Magnetic field strength | Bridge resistor |
|---|---|---|---|---|---|
| AA745 | Chip, SIL6, LGS6S | 13 mV/V | ±2 mV/V | 25 kA/m | 1.6 kΩ |
| AA746 | Chip, LGA6L | 13 mV/V | ±0.5 mV/V | 5 kA/m | 1.2 kΩ |
| AA747 | SO8 | 13 mV/V | ±2 mV/V | 25 kA/m | 3.2 kΩ |
AA745
The AA745 FreePitch sensor is available as an automotive qualified component for chip on board processing. For the industrial sector, the sensor is also available as a component suitable for SMD assembly in the very compact LGA6S or in the slightly larger SIL6 housing.
The connecting pins (pads) are arranged on one side of the sensor, so the off-axis arrangement (e.g. on a PCB edge) is ideal for applications on the shaft circumference and the distance between sensor and measurement scale can be minimized.
The sensor can also be used for applications at the shaft end.
AA746
The AA746 FreePitch sensor is available as a component for chip on board processing in the industrial sector. The sensor is also available as a component suitable for SMD assembly in the compact LGA6L package.
The sensor's connecting pins are designed so that the chip can be fitted to a PCB edge. The sensor can also be used for applications at the shaft end.
With a magnetic field strength starting at 5 kA/m, the sensor can be used for very large working distances or in combination with magnets with low field strengths.
AA747
The AA745 FreePitch sensor is available as an automotive qualified component in the SO8 housing for SMD assembly.
The sensor is distinguished by its electrically isolated bridges for sine and cosine signals. The sensor is optimized for the typical application of measuring with a dipolar magnet at the shaft end.
Data sheets
- AA745
FreePitch sensor for the shaft circumference
- AA746
FreePitch sensor for low field strengths
- AA747
FreePitch sensor for the shaft end
Product information
- AA700 brochure
Product information on the AA700 FreePitch sensor family
Application information
- AA700 Application information
Application information on the AA700 sensor family
CAD drawings
- AA745
3D PDF file
Your contact person
Design features
Sensitec is increasing the sensor efficiency by means of various design modifications to the chip layout. The patented solutions, described more closely below, also contribute to better signal quality, reduced sensitivity to stray fields and increased control accuracy.
FreePitch
FreePitch sensors have been optimized to the extent that they can be used independent of the pole length of the measurement scale. This has the benefit of them being particularly compact and coming very close to a point sensor. They are the ideal choice if a particularly cost-effective solution is needed for the measurement task. In order to keep the dimensions as small as possible, the Wheatstone bridges are nested within each other. In order to generate the sine/cosine signals, both bridges are positioned at an angle of 45° to each other.
FreePitch sensors can be used with pole rings or linear scales with almost any pole length, as well as with dipole magnets.
PerfectWave
The PerfectWave design is applied in order to optimize the signal quality of the FreePitch sensors. The MR strips that serve as resistors have a curved form which is used to filter the harmonics when mapping the magnetic field direction in an electric signal. This filtering is implemented using the special geometry and arrangement of the MR strips and does not cause any additional signal propagation delay. The PerfectWave design is particularly effective for small magnetic fields and results in improved linearity, higher accuracy and better signal quality.