Datasheet

HMC1501/1512

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To interface with output pins of the HMC1501 (OUT+, OUT-), an instrumentation amplifier circuit is typically used.

Instrumentation amplifiers can be purchased as complete integrated circuits, or constructed via combinations of discrete

components and integrated circuits; such as operational amplifiers (op-amps). The purpose of an instrumentation amplifier

is to derive the difference signal (OUT+ minus OUT-), and to provide additional signal amplification as desired. The figure

below shows a typical instrumentation amplifier circuit using an op-amp with external discrete components.

With a typical HMC1501 position sensor, a low cost operational amplifier (e.g. LMV358) could be used as a differential

amplifier shown in the schematic above. The 10 kilo-ohm input resistors present a high impedance from the Wheatstone

bridge, and the 249 kilo-ohm resistor set the amplifier gain and bias at 25V/V and 2.5 volts respectively. The 0.01

microfarad capacitor is placed in the feedback loop to low system bandwidth and to further exclude noise outside the

sensor and amplifier circuits. The analog output voltage of the amplifier is typically fed to an Analog-to-Digital Converter

(ADC) stage stand-alone or within a microprocessor integrated circuit. A recommendation of 10-bit ADC circuits or higher

is expected.

For angular measurements, the same information applies, except the mechanical arrangement changes a bit.

Microprocessor

With ADC

HMC1501

+2.5V

10.0k

249k

Op-Amp

.01 f

+5.0V

Analog

output

OUT+

OUT-

Vbridge

Gnd2

Gnd1

ADC0