1. The 7342 has its own CPU that's running multiple tasks in a time sliced model. One of the time slices is used for host communication. The PID algorithm is running on a seperate DSP. Thus host communication and PID control don't interfere with each other. So the preliminary answer is yes, you can run PID control and data acquisition in parallel.
2. As you need to acquire position and force simultaneously the only way to do this is with only a 7342 in the system is doing a software poll. You should expect a maximum poll rate of about 200 readings per second.
There are some drawbacks here:
a) Jitter. The CPU on the 7342 is running its own cycles that can't be synchronized with the reading cycles of your host system (this won't be improved by LabVIEW RT)
b) Synchronization. You can't make sure that you get the 100% exact correlation between force and position.
c) Accuracy. The ADCs on the 7342 are 12 bit and can't be calibrated. Still you could do a software calibration.
3. I don't understand exactly what you mean with this question:
"can we also send the position control signal for the PID loop to the card?.
You can always send commands from the host to the board. This won't affect your reading rate significantly.
4. As you can tell from 2.) I don't think that this hardware setup would be the ideal solution but if the specs I provided meet your requirements just go for it.
If your standards are a bit higher NI can provide much better options for doing the measurements at low cost even without the need of using LabVIEW RT.
Even the cheapest M-Series board, the
NI PCI-6220 provides superior accurracy (16 bit, calibratable) and performance (250 kS/s, hardware timed, DMA transfer)as well as direct quadrature encoder connectivity and buffered position measurement modes. I would highly recommend choosing this or a similar board for your measurements. You also can synchronize the two measurements in hardware.
Best regards,
Jochen Klier
National Instruments Germany