Kelvin shunt with AD5253

Hi,

I'm amplifying the output of a 100mohm 4 terminal (kelvin) shunt with the AD8253.  I'm using a lab quality calibrator as the signal (current) source.  Problem I'm having is when injecting a DC current through the shunt; I have a lot of 50Hz coupling into the output of the AD8253.  Measuring with a scope accross the inputs shows no 50Hz content.  I have tried a variety of bias resistors from inputs to AGND (as low as 10k).  Injecting a 50Hz current results in a output signal that beats with mains.

How can I minimize this effect with the AD8253?

Regards

Pierre

  • 0
    •  Analog Employees 
    on Dec 19, 2011 11:31 PM over 9 years ago

    Hi Pierre,

    What gain are you using for the AD8253?  My guess would be that the noise is coupling into your system through the input lines and being amplified.  You might not be able to see this with a scope because the 50 Hz noise is below the noise level of the scope before it is amplified.  Are you working with a PCB or still prototyping on vector board?  You can try to minimize 50 Hz noise by minimizing the length of the input wires.  Also, make sure the supplies of the AD8253 are properly  decoupled using 0.1uF capacitors very close to the part.

    Paul

  • 0
    •  Analog Employees 
    on Aug 2, 2018 4:27 PM over 2 years ago
    This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

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    EZ Admin