12-15-2010 03:06 AM
we are thinking to buy a multiplexer to connect to a DAQ unit one one end, and the other end connect to several sensors is it possible to configure the switch unit so that it can auto scan all channels? we hope to have a standalone switch unit that does not require to be connected to PC or control unit once configured, it can run the scan automatically. anyone has any idea how to achieve that with the NI switch, or would recommend other products? Many thanks!
12-15-2010 06:25 PM - edited 12-15-2010 06:26 PM
All of NI's switches actually interface with a PXI or SCXI chassis so they might not be the right solution to your problem. However, if you have a high channel count DAQ card, you can connect your sensors to different channels and the internal circuitry will automatically multiplex through them. If this seems like a viable option, let me know what kind of measurements you'll be making, the expected signal levels, and how many channels you have and I'll make some product suggestions.
12-15-2010 08:47 PM
thank you for your reply.
we are currently using a two 4 channle USB daq module, to run our testing.
but eventually we want to provide the user a series of sensors that only require one channel of daq to accquire data from all sensors in sequence.
usually the user has their own limited number of daq ports and software interface to monitor the signal and output data.
any further suggestion?
12-16-2010 11:56 AM
If you only want to use one channel on your DAQ device you will need a switch, but like I mentioned last time, NI only sells SCXI or PXI form factor switches. If your user/customer is open to using multiple channels, I would recommend a CDAQ chassis (info here) with thermocouple or other analog input modules rather than discreet USB DAQ devices.
12-16-2010 12:44 PM
How many channels would you like to multiplex together (10/100/1000/10000)? If the channel count is low, you might be interested in the cRIO platform, which runs a separate realtime operating system that uses the familiar LabVIEW coding environment. cRIO has an Ethernet port for easy connectivity, but can also store data on its internal memory for later retrieval. We have a couple switch modules that interface with cRIO, but the highest channel count we're looking at is 4 or 8 channels per slot (64 channels total), which isn't very high density. On the cRIO platform, it's actually going to be cheaper to go with an analog input module, such as the 32 channel per slot 9205 (up to 256 channels in a single cRIO).
If you need more channels than this, I'd recommend a PXI chassis(we make chassis in all sizes; see left side of this link for our options). If we use a controller, the PXI chassis becomes a standalone unit. A controller is just like a normal PC, except it's crunched up into a 5x3x8 cube and crammed inside the chassis. We can do up to 3366 multiplexed channels in our PXI chassis, or 1360 AI channels. Pretty sweet!
Let us know which direction you're headed. If you've only got a few channels, I'd recommend getting as many dedicated AI channels as you need.