I am working for a project to counting every photon for about 10 seconds. I used the pci-6602 and a computer with a 2.8Ghz Core i5-2300 CPU and a 16GB RAM. The software is Measure studio 2010 SP1 and NI DAQmx 9.5. But there will be an error: Data was overwritten before it could be read by the system. If Data Transfer Mechanism is Interrupts, try using DMA. Otherwise, divide the input signal before taking the measurement. For average 300kHz input signal, the error appeared immediately, but for average 1kHz input signal, the error still appeared after 3-5 seconds. Here is my setting: myTask.CIChannels.CreatePeriodChannel(counterComboBox.Text, "", Convert.ToDouble(minValueTextBox.Text), Convert.ToDouble(maxValueTextBox.Text), edge, CIPeriodMeasurementMethod.LowFrequencyOneCounter, 0.001, 4, CIPeriodUnits.Seconds); myTask.Timing.ConfigureImplicit(SampleQuantityMode.ContinuousSamples, 100000); myTask.CIChannels.All.DataTransferMechanism = CIDataTransferMechanism.Dma; myTask.CIChannels.All.DuplicateCountPrevention = false; myTask.Stream.ReadWaitMode = ReadWaitMode.Poll; myTask.Stream.ConfigureInputBuffer(1000000); I tried many solutions and changed many setting, but the result didn’t changed. I heard that the on board memory of pci6602 is small, but for 1kHz signal it still can’t work. Please help me to solve this problem. Thanks very much.

Counter/Timer

continous period, overwritten error

Just to be clear, since you currently have a PCI card in a desktop PC, I wouldn't start looking into PXI cards that require a dedicated chassis. The cards I was referring to were the (similar-sounding) PCI-express X-series multifunction series.

Any of them will provide you the counter features you need immediately. They all provide some additional analog and digital capabilties as well, and you should use those specs to help you decide. Unless you're building a locked-down system that won't change for years, I'd recommend buying a card that has a bit more capability than you can immediatley identify a need for. A year from now, it's likely you'll have found a use for some of that extra capability.

Here's a page to start from: http://sine.ni.com/nips/cds/view/p/lang/en/nid/209166

I don't really know how other people have solved this problem. It's not my field and I only have a passing familiarity with things via these forums. I know many people wrote about doing the "binning" method, but I don't think they all viewed it as a compromise. I think that's what they wanted to do in the first place, though maybe that was mainly because it was the only thing they knew to be practical.

-Kevin P

CAUTION! New LabVIEW adopters -- it's too late for me, but you *can* save yourself. The new subscription policy for LabVIEW puts NI's hand in your wallet for the rest of your working life. Are you sure you're *that* dedicated to LabVIEW? (Summary of my reasons in this post, part of a voluminous thread of mostly complaints starting here).