Multifunction DAQ
difference between hardware timed single loop and continuous sample
@vks wrote:
hi
i am taking data from a dc motor through pci 6221 daq card ,processing data in PID loop and then writing the results.
sampling rate is 1000S/s and i am reading single sample in the loop.
my questions are:
1. what is the difference between hardware timed single loop or continuous sample mode in their working? which one is suitable for my application?
2.what is the difference bw sample on demand and N sample read.
3.how to determine the writing rate at which data is being written?
vks
Hardware Timed Single just grabs that sample when requested.
Continuous means that the DAQ board is constantly taking samples at whatever rate you told it. The samples are saved in a buffer. When you perform a read, you are grabbing data out of this buffer. You have to tell the DAQ to stop this task or it will just keep going.
N Sample Read is exactly what it sounds like. When requested, the DAQ reads N samples at the rate you told it and returns it.
It sounds like you want the Continuous Sampling so that you keep your sample rate constant.
What are you writing to? File? Analog output?
If you are just getting a single sample in your loop, you really can't determine your sample rate, especially if you are using Windows. If you need consistant read and write rates, you need to use hardware timing. The would include using the Continuous Sample mode for reading and then writing out waveforms to your analog outputs.
