OM-USB-1208FS User's Guide | Functional Details |
Figure 10. 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. Figure 11 shows the OM-USB-1208FS 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 OM-USB-1208FS 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, neglecting the effect of offset for the moment, 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 of the OM-USB-1208FS for the ±10 V range. This is a graphical version of the typical accuracy specification of the product.
