minimum time period for 6602

[dh]

I'm using 6602 counter with the application of ND_BUFFERED_PERIOD_MSR with countinuous buffer to measure the time period between the consecutive pulses. If I send in constant time period pulse from frequency generator at 300kHz, the board returns "dataLossError" while 250kHz pulses give no error at all. It means the minimum time period is about 3 to 4 microseconds. However, if I send random pulses at 1kHz average frequency, the card sometimes gives "dataLossError". It seems if there is a single pair of pulses with spacing less than 3 to 4 microsecond, the card gives "dataLossError" although most pulse pairs are separated by a long time. Is that right?

Thanks,

[sergesl]

Since you are using the 6602, it means that you can have a source frequency of up to 80MHz as speced at http://www.ni.com/pdf/products/us/4daqsc386-393_386-387.pdf. This means that you can measure periodes in the nanoseconds. I am interested in knowing which signal you have at the source of your counter and which frequency it is.

[dh]

The counter source is 20MHz internal signal. The counter gate is my signal. My signal is the pulses from a single photon detector. The pulses obey Poisson distribution. Theorectically the pulse pair time can be any number larger than zero. Practically due to the detector dead time, the pulse pair is always separated longer than 100ns.

By reading the "transfer rates" part of the manual, I feel something is not right with my device. My computer is Dell PentiumIII 600 MHz Windows 2000. I use 20MHz internal source and 300kHz from a function generator as gate, DMA data transfer. The counter says "data loss". This speed is much slower than what the manual says.

[sergesl]

I would suggest you use a shipping example to measure your pusles. If I recall from your previous post, you are using CVI. So you could go to Help->Find Examples (see screen shot below) and select an appropriate example.

[dh]

I don't have developer zone or DAQmx. Are they free to download?

I have NIDAQ6.9. It includes examples for Visual C. I use the example file "STCsingleBufPeriodMeasure.c" to run the board.

[sergesl]

Yes the driver is free to download. If have CVI 7.1, then you can download and use the latest version of the driver at http://digital.ni.com/softlib.nsf/websearch/90b60d5899bcccdb86256fc700581b89.