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AD8479 as a shunt voltage amplifier in a large DC Motor

Question asked by rdeptyltd on Jul 11, 2016
Latest reply on Jul 14, 2016 by rdeptyltd

We need to monitor the voltage across a shunt in a large DC motor, the Motor voltage is 0 ~ 550VDC and the shunt voltage = 0 ~ 120mV to represent the 0 ~ 1200 Amps flowing into the armature, the signal from the shunt amplifier output will connect to a 3.3VDC analog input on a microprocessor (STM32 Arm Cortex Micro) where the logic is used to control the motor. The concern is that we need to be sure that the output from (for instance) a AD8479 will not damage the analog input on the Microprocessor. The resistance of the shunt is very low due to the current flowing through being very high. Should we be using an AD8217 instead?

We have VCC supply at 3.3VDC or 5VDC or 24VDC.

 

Are we suggesting the correct AD chip for this application? Is there a standard circuit for what we are trying to achieve?

Finally, we could alternatively use a chip with a serial SPI bus if there is such a chip available for measuring shunt voltages without the risk of the ground in the micro being affected by the 550VDC motor supply. The voltage when measured between the shunt and ground is floating, they are not connected in any way.

 

Any advice or assistance would be very much appreciated.

Cheers

Rudy.

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