Ela,
The KS/s stands for Kilosamples per second. The spec is given in this format because the rate per channel is dependent on how many channels you are scanning at a time. This is only true for our E-series boards and the 435x device. Our Scope, Simultaneous-Sampling, and DSA boards have the same spec but the rate is not determined by number of channels that you are scanning.
For example, if I have an E-series board (60xxE board)
that has a sampling rate of 100KS/s this means I can take a total of 100KS every sec spread across all channels. So if I sample one channel I can sample that channel at 100KS/s, but if I sample 5 channels the
max sampling rate of each channel is 100KS/s divided by 5 = 20KS/s.
Again this is not true with the boards that take analog input reading simultaneously. The 51xx, 61xx, 45xx, and 44xx boards have a max samples per second spec, but wether I sample 1 channel or all the channels I can obtain that same max sampling rate on all channels.
For your application I would recommend one of the folloing: The 6110 which can sample up to 5MS/s simultaneously on all 4 channels, which will give you flexibilty for faster acquisitions in the future and it has analog output channels. The board offers 12-bits of resolution on the ADC. With this board you would have to provide your own excitation for the accelerometer.
Or you can use the 4452 board which has 16-bit ADC and can sample at 204KS/s on all 4 channels and provide the excitation needed by most accelerometers from the board. This board does not have any analog outputs on board, but you could always look for a 6711 analog output board when you need analog output capabilities.
Generally speaking the most important factors is choosing a DAQ board is acquisition speed (and your application needs), bit of resolution, and signal conditioning (for example, excitation for accelerometers, filters, etc..). But alot of other factors come into play depending on your transducers and application needs.