A few questions about the USB 621x DAQ

[BTravis01]

Hi,

I'm looking at buying a USB 6218 DAQ board for a testing application, and I just had a few quick questions about it (I'm fairly new to using DAQ hardware).

1. The specs say that the card has 8 static digital IO lines - what does the static qualifier mean in this case?  I want to sample a digital signal at the full 250kS/s, can the digital inputs be used for this? 

2. I want to import the data from the device directly into an Excel document.  How easy / difficult / possible is this to do?

Thanks,

Brett

[Nathan_R]

Hi Brett,

Static digital I/O means that it is not hardware timed. Reads and writes to the port can only be software timed. This means that the maximum read and write rate of the port is limited by how fast your program can run and by bus bandwidth. Also since Windows is not deterministic the timing between samples is not going to be exactly the same.

In order to sample a digital signal at 250 kS/s you will need correlated or clocked digital I/O lines. Currently none of the bus powered M-Series DAQ devices have clocked digital I/O. The externally powered USB M-Series does have clocked digital I/O. I would take a look at the USB-6221. This card however is not isolated like the USB-6218.

The 250 kS/s spec on the USB-6218 is referring to the analog inputs max sample rate. This is for reading a single channel. If you are reading N channels the max sample rate will be 250 kS/s divided by N. For example if you are reading 5 analog inputs the max sample rate is 50 kS/s.

The M-Series DAQ cards use the NI-DAQmx drivers. These drivers can be used in LabVIEW, Signal Express, LabWindows/CVI, ANSI C, and Visual Studio .net. The cards also come with Signal Express LE. Any of these environments can be used to acquire data from the card and then save it in a format Excel will except. I would recommend using Signal Express or LabVIEW.

Let me know if you have any questions and have a great week.

Thanks,