cDAQ counter limitation and a whole bunch of encoders.

[Citabria]

I'm looking for some advice: We have a 16 station test fixture, each with an encoder which is to be connected to a 9401 + cDAQ 9188 chassis. The cDAQ chassis, of course, has a 4 counter limit. The stations will not run simultaneously so I am looking at a cheap and efficient way of switching between each encoder. I was thinking a MUX board but I want to find one with Labview drivers. Any suggestions? Tahnks for the input.

[Beutlich]

The 9401 will expose the counters on the cDAQ chassis, but we also have a module which is a dedicated couner: 9402. If you filled your chassis with these modules, you would have 11 counters. You can add another chassis or a single USB device like the 6341 which has 4 counters.

You can use Analog Inputs to track the values if the code is slow, and then programmatically interpret the analog signal into a ''counted' event. It is much easier to get high count on the cDAQ chassis with Analog or Digital I/O. You can also change to a PXI platform to get cards with higher counts.

There are not any switches on the cDAQ series. There may exist a third party switch device that either has a LabVIEW driver or the driver can be imported, but our switches are mostly for PXI platforms or SCXI platforms.

[Beutlich]

The information above has an error in it that I would like to correct. The 9402 does not have a a counter on the module, it feeds through the counter from the chassis like the 9401. If you want more counters with a cDAQ form factor, you can try cDAQ-9181 single slot chassis each with a 9402. Each 9181 chassis will have 4 counters, so if you get four you will get 16 counters for your application.

[stilly32]

I can't think of a cheap external mux that would be easy to control with LabVIEW. However, you could also just add more 9401s. If you're using three lines per encoder (A,B and Z), you need six 9401s. As you've found, you'd only be able to read 4 encoders at the same time but you'd just change the lines you were reading from. Instead of muxing to one set of lines, let the cDAQ chassis handle all the routing internally for you. You'd just need to use the Counter Input -> Input terminal property for each line to change for each encoder.

 

Hope this helps,

Andrew S