Jan28_2005_2pp

Jan28_2005_2pp - No Class Monday Jan 31st Office Hours 1:10...

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1 January 28, 2005 ¾ No Class: Monday, Jan 31st ¾ Office Hours™ 1:10 – 2:10 pm, Monday, A223 Cook Not next week (no class Monday Jan 31 st !) 1-2 pm, Thursday, 300 Waterman 3-4 pm, Friday, 300 Waterman 2 Tuned Amplification: Chopper Amplifiers ± If we amplify the signal at the modulation frequency , then we can also increase the signal while we reduce the noise: Time Signal, mv 0 6 Time Signal, mv 0 Time Signal, V 0 Time Signal, V 0 6 AB C A : modulate B : C : demodulate
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3 Chopper Amplifiers: In the Frequency Domain 4 Lock-In Amplification ± Tuned (chopper) amplification is limited by stability of f o reference -this limits the effective f to about 1 Hz ± Lock-in amplification tunes the amplifier to both f o as well as the phase of the signal - results in an effective reduction of f to about 0.01 Hz
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5 Signal Averaging ± Need a repeatable signal (time domain method) ± Sum digitally-stored replicate signals ± How does this improve S/N? Signal: increases linearly with number (n) of replicate signals
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Jan28_2005_2pp - No Class Monday Jan 31st Office Hours 1:10...

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