NI USB 6212 - Analog voltage ramp generation

[meiz]

Dear Community Members,

Hope you are doing well. I am new to using the NI USB-2612 board. I am trying to use it to generate a linear voltage ramp.

I know that this board has two analog outputs, a DAC with 16 bit resolution and an output range of ±10V.

By a simple calculation we can calculate the minimum step increase of the analog output (+10V - (-10V)/2^16 = 305µV).

My question is: how can I control the step size each time to a value that I set, for example 305µV ?

Thank you

[Gregory]

Hi meiz, you can generate an array of values to write to the device. For example: [0, 305u, 610u, ...]. Then, when you run the task they will be output in order of the array. I like to use "Ramp Pattern.vi" to generate the values, but you can also use a for loop pretty easily. I believe Ramp Pattern only works if the end value is larger than the start value.

[meiz]

First of all,

Thank you for your answer.

The problem is that I have to control the increment time of each point and I can't do it

Amities

[Gregory]

You can do that. What issues are you having? Can you post the code you have so far? (LV 2016 for me)

[santo_13]

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@meiz wrote:

Dear Community Members,

Hope you are doing well. I am new to using the NI USB-2612 board. I am trying to use it to generate a linear voltage ramp.

I know that this board has two analog outputs, a DAC with 16 bit resolution and an output range of ±10V.

By a simple calculation we can calculate the minimum step increase of the analog output (+10V - (-10V)/2^16 = 305µV).

My question is: how can I control the step size each time to a value that I set, for example 305µV ?

Thank you

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I wouldn't worry about the step size, rather figure out the ramp rate (V/s), and generate a linear ramp (array of voltages) to achieve the ramp with a given sampling rate.

Rule of thumb - slower the ramp rate, the finer the ramp (there is a limit beyond which you will see steps)

For example,

You want to generate a linear ramp 0-10V in 1 sec.

Now, the ramp rate becomes 10V/s, and the smoothness of the ramp now depends on how small the steps are in the ramp.

Choosing a higher sampling rate gives you the smallest step size but is limited by the step size.

With a step size of 305uV, to generate the 0-10V ramp with just 1 point at each step, your sweet spot would be a 32.787 kHz sampling rate. Choosing this rate will take the AO DAC through all successive steps from 0V to 10V.