What Is the Maximum Throughput On My CompactDAQ Device?

Issue Details

How can I calculate the maximum throughput, or data transfer rate, of my cDAQ device?

Solution

The maximum amount of throughput, or data transfer, for a particular cDAQ device is system and device dependent. Below is a summary of the different types of cDAQ form factors and how to calculate the maximum throughput for your device.

USB cDAQ Devices:

The NI X Series DAQ devices and cDAQ devices with a USB 2.0 bus can sustain a throughput of 32 MB/s, while the cDAQ devices with a USB 3.0 bus can sustain data transfer rates of 250 MB/s.

Ethernet cDAQ Devices:

cDAQ devices with an ethernet bus have an actual streaming performance of 32 MB/s. Examples include the cDAQ-9181/85/89 ethernet chassis.

In order to determine whether or not a device can handle the throughput of a given application, you will need to calculate the amount of data that will be streamed across the bus during that application. An example for calculating the data transfer rate of a device is shown below.

Example: suppose you have a 14-slot cDAQ-9179 (USB 3.0) and want to determine whether or not it can sustain the throughput of running 14 NI-9234 modules, acquiring at the maximum sampling rate (51.2 KS/s), across all 4 channels of every device. You could calculate the total data that will be streamed across the 9179's USB bus using the equation below:

Additional Information

The throughput calculation for Digital IO modules (For ex: NI 9474) are same as explained above, but for the Counter IO (For ex: NI 9361), the data transferred from the cDAQ to the host PC over USB would depend on the type of measurement performed. For ex: If doing a edge counting task, the data returned will be a 32-bit Integer at the sample rate defined. Similarly, frequency data is a 4-byte integer and Pulse measurements are 8-byte values.