HELP!!!!! STUDENT IN NEED

Question

Hi everyone, I’m a student who's completely confused using labview. I've a project due in a couple of weeks and it's wrecking my head trying to figure it out. I've got most of it done, but i can't get the rest of it.
I have to modify the attached file to tell a function generator (HP 33120a) to perform a frequency sweep between 100 hz and 10khz with a 1 volt amplitude. The sweep duration has to be 10 seconds and the digital multimeter (hp 34401a) is to be programmed to perform 100 ac voltage measurements. The results are then to be converted into dB and displayed on the front panel as a waveform graph.
Any ideas?
Any sort of help at all would be great. It's a small but annoying part of a big project.
Cheers
Attachments:
lab07.vi ‏47 KB

Answer 1

Well, there's a shipping example in LabVIEW 7 that does exactly what you need but giving it to you as a 6.1 file would probably give you too much. There's a couple of things that you need to do in your example. It's set right now for a single frequency. From a start freq, end freq, and step size, you need to calculate the input frequency in a loop. For example, starting at 100 hz and 100 hz increments, you would set the arb to 100, 200, 300, etc., until the max frequency is reached. LabVIEW has a both a while loop and a for loop. You can enclose your program with either. You also need to change your dmm dunction to read ac volts instead of dc. You don't need to use the dmm to measure frequency because the frequency would be calculated by the VI. Look on the Numeric>Logarthmic palette for a function that you can use to convert your RMS reading from the dmm into dB. Finally, you should use an XY graph to plot the frequency versus gain. The XY graph takes an x array (frequency) and a y array (gain) as inputs. The measured gain and the input frequency can be output from a while loop or for loop and be automatically built into an array. For a while loop, click on the output tunnel and select Enable Indexing. This is the default behavior of a for loop so if you use one of these, you don't have to do anything. I hope that's enough to get you started.