I need some reliable help on the selection of suitable DAQ card (M series preferably) for the following task:
We have a fast ADC (13 bit) that has:
13 digital outputs for bit0...bit12 and
data ready (DR) output (all TTL)
The digital input (TTL) to this ADC is data accepted (DA) that tells ADC when the digital lines have been read and it can put new number on the output.
I would like to use a suitable DAQ card to read those 13 digital lines from ADC when DR makes low-->high transition, i.e. I will use the HW triggered data acquisition. After each digital pattern has been read I need also to send a short TTL pulse back to “data accepted” input line on ADC. ADC has buffer for only 1 sample. The action of sending the short TTL pulse must be also HW triggered with DR low-->high transition.
There will not be more than around 10 000 ADC conversion per second, but sometimes two consecutive ADC conversion might be only 1-2 microseconds away from each other (ADC is converting the pulses from stochastic events).
In addition to this, I also need to count the TTL pulses coming from current-to-digital-integrator, their frequency is max. 10kHz, width 500ns.
There will be no need for any analog input/output.
The program in LabView will act as a MultiChannel Analyzer (MCA) for values coming from ADC. The histogram should be refreshed at least twice per second. The number of counts from the current-to-digital-integrator should also to be displayed with the approximately same rate.
From what I learned so far I need to have the DAQ card that has enough correlated DIOs (I guess at least 13).
Then I guess I also need two counters: one to create single “data accepted” pulse shortly after the “data ready” makes low-->high transition and another one for counting the TTL pulses from the integrator.
I was mostly looking at M series cards (due to pricing) and found that the
PCI-6224, PCI-6229, USB-6229 and PCI-6254 might be suitable due to 32 correlated DIO (port0) but I am not 100% sure those cards are the right selection. I already made one wrong buy (PCI-6221) and I would like to buy the right card now.
Could it be that I miss some ADC conversions if I use USB version instead of PCI?
What DAQ card shall I select then?
with best regards,
Actually all M-Series devices that support correlated DIO have FIFOs - you can check the specs for the cards. I think any of the devices with enough correlated DIO lines will work for your application. The 13 lines acquired on the rising (Low->high transition) is what DAQmx refers to as Correlated DI, where your DR would be the external clock. All M-Series can handle the rates and pulse widths you mentioned. You would need to use a counter or potentially a AI/AO clock from a dummy task to send back the pulse that tells the ADC that the value was read. Another counter would be used for reading.
There wouldn't be a difference in performance between a USB and PCI/PXI card - both would use buffering. The maximum rate for correlated DIO is less on USB, but in all cases if you miss samples you will get an error.
Are you going to be doing any feedback or control based on this?
Multifunction DAQ PSE