National Instruments PC-LPM-16/PnP 사용자 설명서

 

Appendix A     Specifications

PC-LPM-16/PnP User Manual

A-6

 



 

 National Instruments Corporation

 

To illustrate these definitions, Figure A-1 shows a portion of the 
analog-input-to-digital-output transfer curve for an ideal, ADC overlaid 
on the transfer curve of a hypothetical, typical, ADC. As shown in 
Figure A-1, the relative accuracy is the deviation of the code transition 
voltage from the center of the code for an ideal ADC, expressed in terms 
of LSBs. Notice that in this case, an ideal ADC has a relative accuracy 
of 

 

±

 

1/2 LSB, because this definition of relative accuracy encompasses 

both nonlinearity and quantization uncertainties. Integral nonlinearity 
is the worst case deviation of the center of the code from the ideal 
center, expressed in terms of LSBs. Finally, the differential 
nonlinearity is deviation of a code width from ideal code width, 
expressed in terms of LSBs.

 

ADC Errors

Re1

1

x

x

INLe

Re2

2

Output Code (LSB)

-1

1

2

-1

-2

C

ideal

C

actual

V

actual

V

ideal

Practical ADC 
analog-input-to-digital-output curve
Ideal ADC
analog-input-to-digital-output curve

C

ideal

 = Center of code1 for ideal ADC

C

actual

 = Center of code1 for practical ADC

INL error = INLe = C

actual

-C

ideal

Relative Accuracy = Maximum (Rel, Re2)
DNL error = V

actual

-V

ideal

KEY

Input Voltage (LSBs)

 

a.Book : I.Appendix A  Page 6  Wednesday, November 20, 1996  6:36 PM