16 Independant Encoder Measurments

[DJ_001]

Hello,

We're working with the cDAQ platform and we'd like to make 16 independent encoder measurements.  We'll be in the X4 configuration, using A+B and not using Z pulses.

It seams like we can use one NI-9401 to interface with 4 encoders.  My reading of the specs for the cDAQ-9178/9174/9171 indicates that each has 4 counters.

Given this information does that mean that I'd need four chassis with on 9401 to acquired 16 encoder measurements?  Is it possible to configure the counters on the chassis to capture more then one encoder thereby increasing the number of encoders that can be read on one chassis?

Thanks for the help

[ZYOng]

Unfortunately no.

Either you can more cDAQ chassis, or you get a cRIO. With FPGA programming, you can have numerous encoders limited only by your channel count.

[santo_13]

Get two of these and you're good.

https://digilent.com/shop/mcc-usb-quad08-quadrature-encoder-usb-device/

Check out their user manual to ensure you can connect your encoders.

[DJ_001]

ZYOng

Thank you for the suggestion.  I'd thought of that.  However there are a number of downsides:

1) Need to add RT and FPGA software to the project adding cost and complexity

2) The hardware cost is prohibitive

I'll keep this in mind

[DJ_001]

Santo,

Thanks for pointing this out.  This seems like a really interesting device.  And 8 channels at ~$700 is an attractive price point.  Looks like it can be synced with external measurements as well.  This might certainly be worth pursuing...

[DJ_001]

Answering my own question...

Somehow I missed the NI-9361 device during my initial search.

This device has 4 counters eliminating the need to depend on the chassis's counters.  For my use case that would mean a 4-slot chassis with two of these cards.

Total cost would be Chassis: $1483: Cards: $1164*2 = ~$4000

[Kevin_Price]

One note of possible caution about the 9361's: they may not support the kind of timing signal routing you would want to sync with external measurements (or even across the two 9361 modules).

I don' t have personal experience with the 9361, but remember from past threads that they have some unique qualities in terms of *both* capabilities *and* limitations.  When I make a simulated device in MAX, the 'Device Routes' tab shows NO possibility of sharing timing signals to/from or through the chassis.

Be sure to check into this more carefully if you need to sync your encoder sampling.

-Kevin P