5015 sampling rate

[Binar]

Hi NI talented engineers,

I'm using PXI 5015, measurement studio and doing data acuqisition at a sampling rate 40 MHz. The command

niScope_ConfigureHorizontalTiming(vi0, 40000000, 40, 50, 1,,VI_TRUE)

is used to set the sampling rate. However, when we check the sampling signal, it's 60 MHz rather than 40MHz. Same thing happened when it is set to be 50Mhz. The real sampling rate is always 60 MHz. But when we set the frequency going low to 20MHz or 10MHz, it works fine. We're using a 10 MHz external reference clock, and I'm pretty sure the PLL is locked. We do make a check of the locking status.

Is anybody coming with the same problem? Please inform me if you need more infomation about this. Thanks in advance.

Sincerely,

Bin

[Binar]

Hi All,

It looks like a stupid question and I think I get the answer from here http://digital.ni.com/public.nsf/allkb/F44DB529D4AAE670862572980079CB55

Is that means I can only use the following sampling frequency?

• 60 MHz
• 30 MHz
• 20 MHz
• 15 MHz
• 10 MHz

What can I do if I need a 40MHz sampling rate? Any suggestion is appreciated.

Thanks,

Bin

[Andrew.M · Accepted solution]

Hi Bin,

Unfortunately, the only way you can use a 40 MHz sampling rate is if you import it into PFI 1. The divide down method that we use with our on board sample clock only gives you whole number values 1 and greater. 60 MHz is your next best option.

Regards,