UMDAS 0802DA User's Guide

Functional Details

Input Voltage +10V

Output Code

0

8192

16383

-10V

Figure 3-10. Ideal ADC transfer function

The offset error is measured at mid-scale. Ideally, a zero volt input should produce an output code of 8192. Any deviation from this is an offset error.

Figure 3-11shows an example of a UMDAS 0802DA transfer function with a ±2.44 mV offset error. Offset error affects all codes equally by shifting the entire transfer function up or down along the input voltage axis.

The accuracy plots in Figure 3-11are drawn for clarity and are not drawn to scale.

 

 

 

Input Voltage

 

 

 

 

 

 

 

 

 

 

 

 

 

+10V

 

 

 

 

Ideal

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Offset=2.44mV

 

 

 

 

 

Output Code

 

 

 

 

 

 

8192

2.44mV

 

 

 

0

 

 

16383

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Actual

 

 

 

 

 

 

-10V

Figure 3-11. ADC transfer function with offset error

Gain error is a change in the slope of the transfer function from the ideal, and is typically expressed as a percentage of full-scale. Gain error is easily converted to voltage by multiplying the full-scale (FS) input by the error.

3-9