Using NI 9215 as a scope

[glskinner84]

I'm trying to build a virtual scope with labview. I have a NI 9215 I'd like to setup to read two analog channels (x,y), where x is my input in voltage(0-20v) and y is my accelerometer. I previously had these two BNC connectors going into an Allison O-scope II but I'd like to start heading towards a windows environment.

All I would like to do is setup a scope with XT and XY views so I can capture a damping curve.

Is it possible?

[Dennis_Knutson]

Seems like you should not have a problem. Use a normal graph for the x versus time and an xy graph for the other. What have you tried and what problems are you having? Have you tried the DAQmx examples?

[glskinner84]

Creating the VI, I might need a bit of help with, but I think I can pull it off.

I have two issues...

1) Doing a frequency sweep...currently I'm doing this with an analog FG. I'd like to keep it analog. Maybe I can hook an potentiometer to the daq?

2) The 9215 is 10v +-. My y input is going to range from 0-20v. Is there a way to attenuate this voltage before it hit the daq, or do I need to?

[glskinner84]

Or do I just keep using the FG i'm using and just use the 9215 as a scope?

[Dennis_Knutson]

The 9215 only has analog inputs so obviously you cannot use it as a source, let alone as a source to itself. Same as your scope.

Yes, you can externally attenuate the signal. A voltage divider is commonly used.

[glskinner84]

So, let me get this straight. The NI9215 takes analog signals between 10+-. So I would need to use a voltage divider on BOTH signals (x and y) to get the same ratio of curve on my screen. My input (y) goes to 20v but my accelerometer doesn't need to be scaled down....but I would have to do both to keep aspect, correct?

Any advice on how to go about building a voltage divider? Is this a commonplace for these devices?...the need to attenuate the voltage?

[Dennis_Knutson]

No, you only need to scale the channel with the attenuator.

Find an electronics major at your school if you don't understand. A voltage divider is pretty simple - https://en.m.wikipedia.org/wiki/Voltage_divider

[glskinner84]

But I'm attenuatiing AC voltage....maybe I can buy a travel plug that converts 220v to 110v and wire it backwards?

[Dennis_Knutson]

That makes absolutely no sense to me. What are your objections to a simple resistor divider? What is the frequency you are measuring?

[glskinner84]

the frequency of the AC voltage is 60hz, I would assume. I had input from one of my colleagues to use a scope probe in order to dumb down the voltage.

I had another question though: How do I manipulate a graph to change the seconds per divison to control my timebases on a sinewave?