USB-1208FS-Plus-OEM User's Guide
Functional Details
17
Figure 11 shows the transfer function with gain error. Gain error is easily converted to voltage by multiplying
the full-scale (
FS
) input by the error.
The accuracy plots in Figure 11 are drawn for clarity and are not drawn to scale.
Figure 11. ADC Transfer function with gain error
For example, the USB-1208FS-Plus-OEM exhibits a typical calibrated gain error of ±0.2% on all ranges. For
the ±10 V range, this would yield 10 V × ±0.002 = ±20 mV. This means that at full scale, and neglecting the
effect of offset, the measurement would be within 20 mV of the actual value. Note that gain error is expressed
as a ratio. Values near ±FS 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 Figure 12, we have a plot of the error band for the ±10 V range. This is a
graphical version of the typical accuracy specification of the product.
The accuracy plots in Figure 12 are drawn for clarity and are not drawn to scale.
Figure 12. Error band plot
