AG920-07E NVE, AG920-07E Datasheet - Page 86

• Manufacturer Part Number: AG920-07E
• Description: KIT EVALUATION GT SENSOR
• Manufacturer: NVE

Specifications of AG920-07E

• Sensor Type: Magnetic. GMR (Giant Magnetoresistive)
• Interface: Analog
• Embedded: No
• Utilized Ic / Part: ABL & AKL Series GT Sensors
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Supply: -
• Sensitivity: -
• Sensing Range: -
• Other names: 391-1063

When a magnetic field is applied to R2, its resistance will vary in a generally linear fashion with the
applied field, from zero up to the saturation field (Hsat). After the GMR material’s saturation field is
reached, applying additional magnetic field will not result in changes to the resistance of the device.
The complete equation for R2, taking into account both the changes in % GMR with temperature and
the changes in Hsat with temperature, and assuming operation of the sensor element at magnetic fields
less than the Hsat value, is given below:
R2 = R2
Where:
Please note that although the equations provided above result in linear results, the actual GMR devices
are not perfectly linear. In particular, the transition of the output characteristic as it enters magnetic
saturation is rounded, and can be seen in the temperature performance graphs of the various GMR
materials shown at the end of this section. In addition, non-linearities also exist in some cases near the
zero field range of the devices. The best fit for the formulas provided above is in the linear operating
range of each sensor element as defined in the product specifications.
In addition, the effects of flux concentration and shielding in the sensor element are not reflected in
these equations, nor is any effect from hysteresis included.
In many cases, an analysis of the complete temperature characteristic of the device is not required; the
only important parameter is how the output of the sensor device itself changes with temperature. In this
case, it is important to know if the sensor is being supplied with a constant voltage source or a constant
current source. If a constant current source is used, the voltage across the sensor can increase as the
resistance of R1 increases with temperature, thus mitigating some of the signal loss effects with
temperature.
NVE has defined the following two terms to describe the change in signal output with temperature:
TCOV: Temperature Coefficient of the Output with a constant Voltage (V) source; given in %/°C.
TCOI: Temperature Coefficient of the Output with a constant Current (I) source; given in %/°C.
These numbers will provide an accurate indication of the change in the output of the parts over
temperature in the linear operating range. Note that this data is provided for NVE’s AA and AB type
parts but not for any of the parts that include a signal processing IC in the package. This is because
NVE typically builds temperature compensation circuitry into the signal processing IC.
AF = Applied Magnetic Field
HsatT = Hsat@25°C * [1 - (TCHsat * (Temperature - 25°C)]
Zero Field
* [1 - (AF / HsatT)]
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Application Notes