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Author Topic: Reading 0-100 mV signal  (Read 2268 times)
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After messing around more with the LM358s and not getting expected results, on the advice of an EE friend I'm looking into an instrumentation amplifier.  The AD623 is a rail-to-rail device that will work in a single-supply mode, and seems to be giving much more sensible results.  It is, of course, quite a bit more expensive than the LM358, but a few dollars each is still pretty reasonable.  Thanks again for all the help on this.
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Lacey, Washington, USA
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You don't need a rail-to-rail Op Amp, you need a differential amp.

http://forum.arduino.cc/index.php?topic=205229.msg1567471#msg1567471
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Steve Greenfield AE7HD
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Narvik, Norway
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an "opamp" IS a differential amp.
Any rail-to-rail able to run from 5V will do for this job.  Find the cheap one, add a handful of resitors (and a cap or two) and calibrate.
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Ny

Lacey, Washington, USA
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OK, an Op Amp wired as a differential amplifier. The circuit that the OP posted is wired as a single ended amplifier.
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Steve Greenfield AE7HD
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Although an instrumentation amplifier is not an op-amp (per Analog Devices' app note on instrumentation amps), what's the practical difference, in this application, between using an op-amp wired as a differential amp, and using an instrumentation amp?
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Victoria, Australia
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http://www.siliconfareast.com/inamps.htm

Hi, hope this link helps with op-amps and instrument amps,

Tom....... smiley
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Lacey, Washington, USA
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Quote
Of course, an operation amplifier may be utilized as an instrumentation amplifier.
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Steve Greenfield AE7HD
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