So what drives the decision to split or not to split the burden resistor on a current transformer when using a differential ADC like the MCP3911 or the AD7753?
I presume that the common mode issue may also explain why Analog attaches Neutral directly to one of their ADC inputs (see p. 5 of the application note for the AD7753) for the purpose of line voltage measurements. Another explanation is the benefit of fewer drop resistors being required...My voltage sensing is done through a tiny transformer. Do you reckon that I should ground one of its outputs per the Analog recommendation and then use the (much smaller) drop-down resistors for the input signal? Currently, I have two parallel paths to the analog inputs, both featuring a 36k resistor in series and a RC filter (1k and 100nF). The analog application note suggests dropping the second line and just keeping the two RC networks. Interesting!Another option could be to use a transformer with a center tap on the secondary for analog ground. Then run two lines to the ADC as before, but this time with 2x resistance since the output voltage effectively doubled (2x6V vs. 1x6V output).
I'll measure the primary resistance on the transformer and try your suggestion. That will require a higher-voltage resistor like a 1W flameproof model, right?