Estimate the data produced by acquisition
Start with active channel count, sample rate per channel and bytes stored per sample. The approximate uncompressed payload rate is sample rate × active channels × stored bytes per sample. Storage format matters: a 14-bit ADC may still place each sample in a 16-bit word. Confirm the actual driver or file format.
For example, two channels at 500 MS/s with two bytes per sample produce 2,000,000,000 bytes per second, or 2 GB/s in decimal units, before additional metadata or transfer overhead. Ten seconds would require about 20 GB of sample storage. This is a planning calculation, not a measured CCDAQ streaming specification.
Distinguish capture memory from continuous recording
Onboard memory can hold a finite acquisition record. Continuous recording also requires the interface, driver, host memory, processing and destination storage to keep up over the required duration. A large buffer can absorb some temporary imbalance but does not remove a sustained throughput bottleneck.
Choose the interface as part of the complete system
For PCIe DAQ cards, check the required slot, lane configuration and host platform. For USB modules, check the controller, connection and competing traffic. For RJ45 or optical modules, confirm the protocol and supported host connection. A 10G optical interface does not by itself mean 10 Gigabit Ethernet, nor does its nominal link rate guarantee the same application payload rate.
Define a meaningful evaluation workload
- Use the intended channel count, sample rate and sample format.
- Include triggering, processing and file-writing behavior.
- Run for the intended acquisition duration and monitor dropped data or buffer overruns.
- Record the host hardware, interface configuration, driver and software versions with the result.
Request the supported acquisition modes and sustained-transfer information for the exact model and configuration. Separate a theoretical bandwidth calculation from a tested recording result.
Compare PCIe cards and modular DAQ instruments · Discuss host and software requirements