Noise, signal/noise ratio,

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Lecture 4

• Noise, signal/noise ratio,
• detection limit

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Standard analytical terminology
Electronics
Value (mean, average) Standard
deviation Relative standard deviation(RSD)
Signal Noise Signal-to-noise ratio (S/N)
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A noisy set of data
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Less noisy measurements. Signal is well visible.
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Sine wave a primitive model of a noisy
experiment
Peak-to-peak noise 3 s (approximately)
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Noises
Thermal
temperature
bandwidth
resistance
Shot (quantum)
current
Flicker
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Environmental noise
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What should I do to reduce the noise?
A simple filter
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Removal of the amplifier noise by filtering
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Computer can help
Boxcar averaging
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c a b
Random numbers a and b
sc ?
c a a
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And this is number of measurements
This N stands for word noise
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A one measurement, S/N4 B 100
measurements(scans), S/N 40
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Limit of linearity
intensity
10s/slope
3s/slope
Limit of quantitation (limit of determination)
Limit of detection (detection limit)
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concentration