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Why does this type of accelerometer need split supply. In the data-sheet this is described as a excitation voltage. But the diagram they provide does not show any +/- rails or any excitation Wheatstone bridge ect.

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I cannot find any illustration about this type of accelerometer. And their data-sheet is not clear as well.

How can we illustrate this type of accelerometer along with their +- power/excitation connections? What is being excited here? Are +- power inputs supply anyother unit besides the opamp rails?

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  • \$\begingroup\$ Think about the "Servo amp" as a dual supply OpAmp, if you feel better with that... The datasheet is telling that the output is +/-5V. That should be a sufficient reason. \$\endgroup\$ – Eugene Sh. Oct 12 '17 at 19:41
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Don't forget that acceleration is a signed quantity and can be positive or negative.

The data sheet states that the output is +/- 5V - it needs the negative supply to be able to do that.

Also the negative current is needed for the torque motor to generate a negative torque.

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This type of accelerometer is the force-balancing type. The servo is attempting to keep the test mass on the end of the arm in a fixed position, while any external physical force on the system is attempting to move it. If the servo succeeds in keeping the mass still, that means that the force applied by the servo (which is proportional to the current through the actuator) is equal to the external force. Since the current is easily measured, you now have a force (acceleration) sensor.

Since the force might be either positive or negative along the sensitive axis of the sensor, the current through the motor must also be able to be either positive or negative, and the resulting output signal can swing positive or negative, too. All of these things dictate the need for a bipolar power supply.

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