How can i find out the resolution and accuracy of PXI-6602 module?

[chandhu]

I have a 32 bit  8 channel PXI-6602 counter module.  PXI card is interfaced to PC with MXI-4 link. How can i find out the resolution and accuracy of this system.What is the maximum accuracy and resolution i will get from this system. Because optical signal to cmos conversion signal is given as a input to the counter.

[Ed W]

Hi chandhu,

Were you referring to the accuracy of the count register or the timing clock? 

PXI-6602 specifications can be found in the NI 660x Specifications.  The resolution of the count register is, as you’ve noted, 32 bits.  This corresponds to a maximum count value of 4,294,967,295.  As long as all of the edges are in accordance with TTL specifications, the accuracy of the count register is 100%.

On the other hand, the PXI-6602 baseclock accuracy takes on the baseclock accuracy of the PXI CLK 10 signal.  Again, this is all found in the specifications.

You may also want to check out the NI 660x User Manual – it contains a lot of details on the operation of these counter/timer devices.

I hope this helps.  Please post back if you have further questions.

Ed W.

Applications Engineer

National Instruments

[acanivell]

Hi Ed

I am also trying to see how much accurate I can go with a 6602 (and also with a 6208)

As I can read from the manuals:

- 6602 has max timebase 80Mhz and stability 50ppm. 80Mhz*50ppm = 4Khz accuracy

- 6608 has max timebase 10Mhz and stability 75ppb. 80Mhz*75ppb = 6Hz accuracy

My question is:

If I only use a timebase clock of 100Khz, then would accuracies be the following?

- 6602: 100Khz*50ppm = 5Hz accuracy

- 6608: 100Khz*75ppb = 0.0075Hz accuracy

I hope you can give me a hand with this!

Regards

[cs_BOT]

I think ppm/accuracy is not affected by what timebase you take.

[acanivell]

Hi csbot

That would mean that I can never make a frequency estimation with accuracy 0.1Hz , no matter the range of the signal being measured.

But there are frequency counters in the market (see Agilent's) that can measure frequency at this accuracy, so it should be possible also with NI equipment, isn't it

I think I am missing something in my calculations ... Any ideas?