Value-priced DAQ devices traditionally can sample analog signals at high hardware clock rates, but digital and frequency/encoder signals are sampled less often, and are usually software paced. Sampling signals at different rates can make for difficult data alignment and decrease the timing accuracy of any decisions made by the program. However, select MCC DAQ models, such as the USB-1808 series, support synchronous sampling. Now analog input (AI), digital input (DI), and counter input (CI) channels can all be sampled at the same rate. The USB-1808 features 8 true simultaneous AI channels, and its architecture also accommodates DI and CI data latched by the same clock edge up to 200 kHz, with all data buffered gap-free and periodically sent to the host application.
The recently enhanced Encoder VI support in our ULx for NI LabVIEW driver complements the USB-1808 well, and now LabVIEW developers can take advantage of the power of the USB-1808 to easily sample encoder position or angle in conjunction with both analog and digital signals, all synchronously. Below is an example of this implementation. The block diagram shows all 3 channel types being configured in one task to share the same sample clock and sample continuously.
The front panel displays the same two second snapshot of all 3 data types.