NI 5412 PXI: Amplitude resolution 3 digits

[ampm]

 Hello,

what does "Amplitude resolution 3 digits" in NI 5412 PXI specifications (http://www.ni.com/pdf/manuals/371468a.pdf) mean and how does it relate to the 14 bit DAC resolution of 5412?

Thanks.

Message Edited by ampm on 11-02-2006 12:35 PM

[AnalogKid2DigitalMan]

Here's a link regarding bits and resolution (I presume it apples to DAC's analog outputs too)

http://zone.ni.com/devzone/cda/tut/p/id/3295

For 14 bits, I come up with 4.8 digits. I wonder if the 3 digits mentioned takes noise and other factors into effect (Effective Number Of Digits).

Hopefully someone from NI will join in.

[ampm]

Thank you.

I hope than NI people can answer these and some other questions.

For 14 bits, I come up with 4.2 digits by the formula log10(2^14).
3 digits would correspond to 10 bits according to this formula.

If I need for example to generate arbitrary waveform which amplitude varies in the range 20 mV - 700mV what is the smallest 'quantum' of the amplitude change I can get using 5412 board? Will it be 700mV/(2^10) or 2V/(2^10) or 12V/(2^10)  or some other value?

Thanks again.



 

[Jesse_O]

Hello,

The 5412 generates a waveform with a 14bit DAC, however the 3 digits specification refers to the resolution of the signal amplitude.  For example if you have a signal between +/-1V, this 1V signal will will have 3 digits of resolution, however you will still have the 16384 steps defined by the 14 bit DAC.  This means that you can increase your amplitude in steps of 0.001.

Regards,

Jesse O.
Applications Engineering
National Instruments

[ampm]

 Hi,

Do 3 digits correspond to log10(2^10) or 10 bits ?

Does it mean that for a 0.1 V peak-to-peak signal the possible amplitude increase will be 0.0001 V?

What about 10mV signal when the steps should be 10 uV? Can 5412 do this?

Does the choice between Low Gain Amplifier and High Gain Amplifier of 5412 affect the value of the amplitude step?  Is this value solely determined by the amplitude of the signal one gets at the output of 5412 ?

Thank you.

[ampm]

Hello Jesse,

could you please give some links to the NI (or other) documentation where these topics are explained.
I failed to find relevant ones myself but I am really curious..

Thank you.

[Jesse_O]

Hello,

The three digits corresponds to the maximum output voltage.  For example if you have a 1V sine wave you have an accuracy of 1V +/- 0.001V.  This 1V sine wave has 14 bits of steps to define the resolution.  The 3 digits (10 bits) is only for the maximum voltage due to the attenuators used to define the range.

If you look inside the manual for the 5412 on page 2 you can see that the minimum output range is 5.64mV.  This 5.64mV range has a resolution of 14 bits, which gives you more than 10uV resolution.  You are also correct that if you use the low gain path you will get better resolution since the low gain has a minimum output voltage rage of 5.64mV and the high gain has a range of 33.8mV.

I hope this clarifies things,

Jesse O.
Applications Engineering
National Instruments