sample rate NI-5114

[BABAY]

Hi all!

I have max sample rate 250MS/s for NI-5114, but I need to know all valid values for this parameter. How can I calculate them?

Any help appreciated...

[BABAY]

up

[Evrem_Y]

Hi Babay,

I copied the following from the NI High-Speed Digitizer Help:

Decimation Method

In the decimation method, the ADC samples at the rate of the onboard clock and then sends its digital data to a decimator that essentially discards samples at a specific interval to achieve slower effective sampling rates. The valid sampling rates are always an integer divisor of the onboard clock. For example, if the onboard clock is 100 MHz but you want to sample at 25 MS/s, you must use decimation. The decimation method would discard all data except for every fourth datapoint to achieve exactly 1/4 of the maximum sample rate (or onboard clock rate).

Divide Down Clock Method

Some oscilloscopes use the divide down clock method. In this method the onboard clock is sent through a series of clock dividers, and then that clock is sent to the ADC. Typically, the decimation method is preferred over the divide down clock method.

Note  NI high-speed digitizers support the decimation method but do not support the divide down clock method.

You can find this section in NI High Speed Digitizers Help->Fundamentals->Clocking->Sample Clock

The decimator has 16 bit, that means the sample rate range starts at 250MS/s and ends at 3,815kS/s.

I hope it helps.

Evrem

NI Switzerland

[BABAY]

I don't know how I didn't find it earlier, but any way thank you...

[BABAY]

---

@EYCH wrote:

Hi Babay,

I copied the following from the NI High-Speed Digitizer Help:

Decimation Method

In the decimation method, the ADC samples at the rate of the onboard clock and then sends its digital data to a decimator that essentially discards samples at a specific interval to achieve slower effective sampling rates. The valid sampling rates are always an integer divisor of the onboard clock. For example, if the onboard clock is 100 MHz but you want to sample at 25 MS/s, you must use decimation. The decimation method would discard all data except for every fourth datapoint to achieve exactly 1/4 of the maximum sample rate (or onboard clock rate).

Divide Down Clock Method

Some oscilloscopes use the divide down clock method. In this method the onboard clock is sent through a series of clock dividers, and then that clock is sent to the ADC. Typically, the decimation method is preferred over the divide down clock method.

Note  NI high-speed digitizers support the decimation method but do not support the divide down clock method.

You can find this section in NI High Speed Digitizers Help->Fundamentals->Clocking->Sample Clock

The decimator has 16 bit, that means the sample rate range starts at 250MS/s and ends at 3,815kS/s.

I hope it helps.

Evrem

NI Switzerland

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Ok. If the decimator has 16 bit, then the sample rate range should start at
250MS/s
and end at 3,815kS/s.
But that's wrong. I set different s.r. and got following results (actual
s.r.):
scope->setSampleRate(100) //actual sample rate is 954
scope->setSampleRate(1000)//actual sample rate is 1000
scope->setSampleRate(1500)//actual sample rate is 1500.01
scope->setSampleRate(1501)//actual sample rate is 1501.01
scope->setSampleRate(100059)//actual sample rate is 100080

These  values cann't be calculated by dividing of 250 MHz on any integral
value. Furthermore I didn't find any appropriate attribute for Decimation except R/O Combined Decimation, but appearently this is not what I need.

Does anybody have an idea?