Hi
I have a DAQ setup that uses the following:
- Chassis NI cDAQ9188
- NI 9411
- Quadrature Encoder
I want to make continuous buffered measurement of position reading from the quadrature encoder. I first set up a task in NI MAX:
- It works if I configure my signal as 1 Sample (On Demand).
- It doesn’t work if I change to Continuous Samples (Use digital input sample clock as the external sample clock). I received Error 200284, which indicates not getting enough samples within the Timeout period.
- The only Sample Clock it accepts seems to be the 100kHz Timebase, and the sample rate needs to be 100kHz as well. This is too fast for what I need.
To simply the problem, I changed the task from position measurement to edge counting. The problem still there.
- I tried running the Counter – Count Edges (Continuous Clock).vi shipping example, the result is still the same.
- I have read up about the buffered continuous edge counting; it only says that an external sample clock is required, doesn’t go deeper beyond that.
- I have checked the KBs:
- DAQ Assistant Edge Counting Error for N Samples or Continuous Samples
- DAQmx Read VI Error -200284 Samples Have Not Been Acquired
- Neither of them really answers my question.
Since I can acquire edge counts if the task is set to “On Demand”; I would say the hardware is configured correctly.
It seems that when the task is set up as continuous buffered acquisition, then it needs an external clock to drive the data acquisition, which is fine. My question is: Why does it only accept the 100kHz Timebase and nothing else? It seems that it will not accept the external sample clock unless it’s the 100kHz timebase (and sample rate = 100kHz). With no sample clock => no samples acquired => Error -200284.
Continuous sampling works in simulation mode. I can use any sample clock, but with thee actual hardware that I have, it only works with 100kHz Timebase.
I have checked the routing of the sample clocks, the counter sample clock seems to support all external clocks.
Any ideas?