6070e transfer rate

[Manuj]

Hi,
I have a Daqpad 6070e for firewire Multifunction DAQ.
It is supposed to have a 12 bit accuracy and a speed of 1.25MS/s.
This is where i get confused....12 bit accuracy X 1.25MS/s = 5120Mbits/s of data
but the firewire is only supposed to have a speed of 400Mbits/s   so does that mean that the device discards the rest 4720 Mbits of data per second, which I doubt as NI will not be dumb enough to design a device in such a way. Hence there is something that i dont know, but what ...   can someone please tell me.

Manuj

[devchander]

 Hi Manuj,

When you refer to Speed of 1.25 MSamples/sec, What you speak about is the maximum sampling rate the input circuitry can digitize the analog signal or the card can sample sample that many individual samples in a second.

if you use 1 channel out of 8 channels in the 6070, you can go to a max sampling rate of 1.25 Msamples /sec

If you are using 8 channels also you can go fro a sampling rate of 1.25Msamples/8 = approx 156.2 kilosamples/sec( Ignoring the settling time considerations)

Where as, Resolution is the number of bits that the ADC uses to represent the analog signal.

The higher the resolution, the greater the number of divisions the range is broken into, and therefore, the smaller the detectable voltage change for a given input range and gain. The smallest detectable voltage change for an ideal DAQ board is determined by: Smallest detectable voltage change = range/(gain*2^resolution)

If you select the ADC range as +/_10 V, since your card has 12 bit resolution, The ADC is scaled to represent +/-10 V in 4096 steps where each step= 4.8 mV

Hence the 12 bit resolution determines how accurately you can measure an input signal.

Hence,  they both are independent characterstics and do not correlate in the way you have understood it.

Hope this answers your query

Regards

Dev