Measurement Computing USB-1608FS User Manual page 21

USB-1608FS User's Guide
The accuracy plots in Figure 3-9 are drawn for clarity and are not drawn to scale.
0
For example, the USB-1608FS exhibits a typical calibrated gain error of ±0.04% on all ranges. For the ±10 V
range, this would yield 10 V × ±0.0002 = ±4 mV. This means that at full scale, neglecting the effect of offset for
the moment, the measurement would be within 4 mV of the actual value. Note that gain error is expressed as a
ratio. Values near ±FS (±10 V) are more affected from an absolute voltage standpoint than are values near mid-
scale, which see little or no voltage error.
Combining these two error sources in
scale (±10 V). This plot is a graphical version of the typical accuracy specification of the product.
The accuracy plots in Figure 3-10 are drawn for clarity and are not drawn to scale.
Ideal +1.66mV + 4mV
Ideal -(1.66mV + 4mV)
Input Voltage
+10V
32768
-10V
Figure 3-9. ADC Transfer function with gain error
Figure 3-10 , we have a plot of the error band of the USB-1608FS at ±full
Input Voltage
1.66mV
0
Ideal
Figure 3-10. Error band plot
Gain error = +0.04%, or +4mV
Ideal
Gain error = -0.04%, or -4mV
Actual
Output Code
65535
+10V
32768 65535
-10V
3-9
Functional Details
Ideal +1.66mV + 4mV
Ideal
Ideal -(1.66mV + 4mV)
Output Code