Measurement Computing USB-1408FS - Manual (Page 18)

USB-1408FS User's Guide Functional Details
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Figure 13. ADC Transfer function with gain error
Figure 13 shows an example of a USB-1408FS transfer function with a calibrated gain error of ±0.02%, or
±2 mV. This means that at full scale, neglecting the effect of offset for the moment, the measurement would be
within 2 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 14, we have a plot of the error band of the USB-1408FS for the
±10 V range. This is a graphical version of the typical accuracy specification of the product.
The accuracy plots in Figure 14 are drawn for clarity and are not drawn to scale
Figure 14. Error band plot
Synchronized operations
You can run up to two USB-1408FS devices on most computers. You can connect the SYNC pin of two devices
together in a master/slave configuration and acquire data from the analog inputs of both devices using one
clock. When the SYNC pin is configured as an output, the internal A/D pacer clock signal is sent to the screw
terminal. You can output the clock to the SYNC pin of a second device that is configured for A/D pacer input.