Questions regarding analog output

[Qifu]

I want to build a LabVIEW file to generate analog output signal. Basically, if a variable (say, temperature) is between 250 and 500, voltage will be applied to a valve and open the valve. The attached is my first try using LabVIEW. But there is an error:

Error -200077 occurred at Property Node DAQmx Timing (arg 1) in DAQmx Timing (Sample Clock).vi:1->pulse based valve control.vi
Possible reason(s): Requested value is not a supported value for this property.
Property: SampTimingType
You Have Requested: Sample Clock
You Can Select: On Demand
Task Name: _unnamedTask<2>

The DAQ device I used is USB-6009. I tried different sample modes, but nothing worked. How can I fix this problem?

Also, for the next step, I will use AI (temperature) and AO (voltage) in the same LabVIEW file. Here are some other questions.
1. Is it necessary to set sample rates for the AI and AO channels?
2. Is it necessary to synchronize the sample clocks for AI and AO channels?

Thanks,
Bei

[Qifu]

Sorry, I forgot to attach the .vi file.

[Robert_F]

Hi Qifu,

If you are new to LabVIEW and DAQmx, I would suggest reading this tutorial. The shipping examples are also a wealth of knowledge.  (Help >> Find Examples >> Hardware Input and Output >> DAQmx >> Synchronization >> Multi-

Function)

You did not specify how fast you will be acquiring data.  I will assume that you will be acquiring and generating at a slow rate since you are measuring temperature.  Yes, you should set the sampling rate and sample clocks the same for both the AI and AO.  I would refer to the example (Multi-Function-Synch AI-AO) in the example finder on how to accomplish this.