Software clock and hardware clock

[somewei]

Hello friends,

Here I got a problem while acquiring data in DIAdem  from NI SCXI-1000DC through DAQ card 6062E.  The problem is I can only run the DAC model after I set the clock unit as a hardware clock. And with a 250Hz hardware clock, the accquired signal display in the graph display unit seem not so smooth, they jump forward. If I increase the clock rate up to KHz, things get better, the signal disply goes smoothly as time goes by, but I do not need such frequency for data record, it is too high. I remember I used run such data acquisition with a software clock before reinstallation of the XP system and DIAdem a few days before. Are there anything I missed?  For each clock unit in a DAC model we can configure it as a software clock as wll as a hardware clock, what is the difference between thses two configuration?

Best regards

Somewei

[yankaini]

software is less reliable than hardware. Generally, we recommend hardware timing

[somewei]

Thanks for your reply Trusted Regular, I got the same information from the DIAdem help document.

Then how to make a choice between this conflict? In the control model the NIDAQ input unit and the data record unit must use the same clock, if frequence of this clock is set to a low value(for example 250Hz) to suit the data record then the signal display on DIAdem visual panel seems not so smooth but jump forward, and the display response to input signal change with a lot of time hysteresis. If I set the clock to a high frequence( for example 3KHz) to get better signal display, then this frequency is really too high for data record, I will get a big data file with a lot of unnecessary data and the data analysis software will get a load workload wich will spend much more time as well.

The gap is a bit too big to make a eclectic frequency for me. 

There must be some solution I don,t know for this problem I think.

The hardware for data acquisition are NI DAQ card 6062E, SCXI-1000DC,SCXI-1313

Related software are NI DAQmx v8.0 DIAdem V9.1

[Walter_Rick]

Hello somewei,

The Hardware-Clock is generated on the hardware. That guarantees a stable, exact and fast clock rate. The Software-Clock is generated in the PC. This is a stable and exact too, but normally limited at 1000 Hz. If you would like to control something (with an output channel) then you must use the Software-Clock.

To solve your problem you have several possibilities. You can measure fast and use the control block Time to store only every n seconds a value. Alternatively you can use the processing block "Signal Copy" with an own clock rate. Please refer to the attachment for details.

Greetings
Walter

[somewei]

Thank you so much Mr. Walter, that is exactly what I am looking for.