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On page 14 of the AMC1200 datasheet there is a diagram showing a voltage monitoring application.
I have a couple of questions regarding this:
1. What is the tolerance of the Rin resistor which is listed as 28kohm in the datasheet.
2. If I include the Rin resitance as part of my calculation for the voltage divider do I still get the extra gain error described by Equasion 1?
3. I am trying to monitor a voltage which is 280Vp, what is the best way to use the AMC1200 to keep the gain error as low as possible.
1) We do not have a distribution for the change in input differential resistance of the AMC1200. If this input resistance plays a significant role in your design my recommendation would be to assume Rin could fluctuate between 24 kohm and 39 kohm from unit to unit.
2) Yes, that is correct.
3) The best way to keep the gain error as low as possible is by choosing R2 as low as possible.
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In reply to Jose Duenas:
In reply to Leonid.Y.Ayzenshtat:
We do not have other isolation amplifiers with higher input impedances.
However, you can include an amplifier in front of the AMC1200; depending on your input offset requirements have a couple of options:
a) You could use a simple op-amp used in a similar way to that used in TIPD129:http://www.ti.com/tool/TIPD129http://www.ti.com/lit/ug/tidu040a/tidu040a.pdf//
b) You could use an instrumentation amplifier like the INA333 in conjunction with the LM7705.
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