the same resolution for different input range in DAQ mx (USB 6251)

[Jaseon]

My input signal range is  - 0.95 ~ + 0.95. I have two problems about that.

1)  When I set the input range as ( - 0.1 ~ + 0.1 ), the resolution is 1mV. When I set the input range as ( - 10 ~ + 10 ), the resolution is also 1mV. What's wrong with that?

2) If the input range is  ( - 10 ~ + 10 ), then the resolution should be 20 volts (total voltage swing) divided by 65536 (16 bits). It shoud be 305 uV. But the smallest voltage that can be detected is 1 mV. What's wrong with that?

Thank you,

[Aaron_W.]

Jaseon,

How are you measuring your signal? Is it possible that the indicator you are veiwing the voltage from is only displaying three decimal places? If you attach your code or a screenshot that would be helpful.

[Jaseon]

Yes, you are right. I find that the data that I collected just has three decimal places. How could I set it and make it could have more decimal places?

Thank you so much!

[Jaseon]

data=importdata('G:\data\01302014\P007.bin');
rmax=numel(data);

for i=1:rmax

      volt_1(i)=data(i);

end

figure

plot(timepid,volt_1,'b');

xlabel('Time (s)');
ylabel('Voltage (V)');

[Aaron_W.]

I'm not familiar with the Matlab programming aspect of the card, I'm guessing the problem is with that and how it's returning data back. I would view the signal in Measurement and Automation Explorer (MAX). Also, where is the second screenshot from? That looks like the DAQ Assistant in LabVIEW, or is this how the acquisition is configured in Matlab? If you are using the Data Acquisition Toolbox it might be a good idea to go over to Mathworks' site and post the question there as they write that software.

[Jaseon]

 You are right.

I find that the data that I collected just has three decimal places. How could I set it and make it could have more decimal places?

[Aaron_W.]

I see you are importing data from a .bin file. How are you creating that .bin file?

[Jaseon]

this is the vi program

[Aaron_W.]

It's with how you are saving the bin file. By default the Write to Spreadsheet File VI uses the format of %.3f which means three decimal places. Try using %.6f as shown below.

This should fix things right up.

[Jaseon]

Thank you so so so much! You are such a nice guy.