how do you set amplitude of pulse train?

[invasion2121]

I have successfully downloaded and executed the sample program shown here:

http://www.ni.com/white-paper/2991/en

and see the pulse train generate in my oscilloscope.  When measuring the value of a pulse high, the oscilloscope says 5V. 

How do I change it to 3?

Looking at the DAQ Create Channel node I don't see any inputs for amplitude, only frequency and duty cycle.

Where is the amplitude of 5volts being set and how can I change it to 3V?

[invasion2121]

I have successfully downloaded and executed the sample program shown here:

http://www.ni.com/white-paper/2991/en

and see the pulse train generate in my oscilloscope.  When measuring the value of a pulse high, the oscilloscope says 5V. 

How do I change it to 3?

Looking at the DAQ Create Channel node I don't see any inputs for amplitude, only frequency and duty cycle.

Where is the amplitude of 5volts being set and how can I change it to 3V?

[g_Ricky]

I think is not possible... The voltage limit of the pulse generation depends on the board...  so you have to look at the board datasheet. Which model of board are you using?

[PaulG.]

You will probably have to level shift with more hardware. 5V to 3.3V level shifter circuits are fairly common.

[invasion2121]

Hi Ricky - 

I am using the DAQ 6259 board.  Do you think pg. 11 is relevant? 

[nathand]

Why would page 11 be relevant? The only reason it mentions 3.3V is to tell you how much current it draws from the host bus on the 3.3V line.

Digital outputs on your device are 5V. It is not a setting you can change.

You could theoretically load the the output channel with a resistor to ground, which would pull down the voltage by increasing current, but I strongly recommend against it. Do it properly by inserting a level-shifting circuit.

[g_Ricky]

Usually I solved this problem with an external transistor, the board leads the transistor with the 0-5V pulse train and the Vcc of the transistor is set to 3.3V. I think it is the easyest and the safetyly way to transform the level of the pulse train.

[invasion2121]

Hi Nathand, and Ricky - 

Do you guys think this website:

https://decibel.ni.com/content/docs/DOC-3545

Could help me? I noticed there is a minimum and maximum value passed in to the Analog Output function.  

I could set the minimum = 0V and maximum = 3V.

I will also look into the level shifter and transistor ideas.

[nathand · Accepted solution]

Sure, you can generate an analog waveform at whatever amplitude you want (within the range of what the board supports), but the counter/timer output is much more appropriate for generating a PWM signal.