S Series and X Series simultaneous sampling devices use simultaneous sampling. M Series, E Series, all other X Series devices use multiplexed sampling.
C Series devices in an NI CompactDAQ chassis use both simultaneous and multiplexed sampling, where all devices in the chassis share the same sample clock. Devices, such as the NI 9215, with an ADC for each analog channel use simultaneous sampling. Devices with a single ADC sample in sequence, using multiplexed sampling. An example of such a device is the NI 9205.
Each multiplexed C Series device has a separate convert clock. The convert clock timing is based on the number of channels for that device in the task, not the total number of channels in the task. You can set the convert clock rate on a per-device basis using the Active Devices and AI Convert Rate attributes/properties on the DAQmx Timing property node. The following figure depicts a ten-channel analog input task on two simultaneous sampling C Series devices and two multiplexed sampling C Series devices with different AI convert rates: