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Analog front end for Process Control Application 16-channel universal input (TC/3-wire RTD/4-20mA/0-10Vdc inputs)

Question asked by PrateekJain-28889 on Jul 19, 2013
Latest reply on Jul 23, 2013 by DerrickH

Hello,

I am designing circuit for 16-channel universal non-isolated analog input . I am using differential multiplexer for channel selection and two more multiplexers to select signal processing block depending on input type(TC/RTD/4-20ma/0-10VDC). At input channel I m providing transient protection using TVS diodes and clamping diodes. Should I put common mode and differential filters at the input connectors after protection  or should place a common filter for all channels  after multiplexer (before instrumentation amplifiers or 24-bit sigma-delta ADC). Using a common filter may reduce channel to channel data acquisition speed, on the other hand placing it for each channel at the connectors just after protection hardware increases number of filters.Please suggest me where should I place  filter?

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