Analog Devices AN-615 Application Notes

9106

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tion of 16 bits or 24 bits. However, the effective number

tive resolution. Analog Devices speci es peak-to-peak

rms

rms noise.

the analog input range decreases. However, since the

full-scale analog input signal is also being reduced, the

the number of  icker-free bits is important. The digital

word from the ADC can then be truncated so that the

 ickering bits are not seen on the weigh-scale monitor.

NUMBER OF OCCURRENCES

RMS NOIS

E

P-P INPUT NOISE = 6.6  RMS NOISE

OUTPUT CODE

n–4n–3n–2n–1nn+1n+2n+3n+4

–2

–

tered trademarks are the property of their respective companies.

to-noise ratio equals

= 20log

Analog Devices normally speci es the peak-to-peak

rms noise. From the signal-to-noise calculation, the

+ 1.76 = 20log

V when the analog input range is

1.25

–6)/(2.56

2)) = –115.85

+ 1.76 =>

= (115.85 – 1.76)/6.02 = 19

 icker in the 19 MSBs.

–6)/(2.56

2)) = – 132.25

132.25 = 6.02

+ 1.76 =>

= (132.25 – 1.76)/6.02 = 21.7

value that is greater than the peak-to-peak resolution by

the amount of bits that  icker. The peak-to-peak resolu-

tion gives a better indication of performance since it

from company to company. Therefore, when comparing

than parts that are speci ed using effective resolution.

that has an effective resolution of 22 bits has a  icker-free