How can I use LabView Signal Express to measure peak-to-peak value of AC voltage?

[newbie87]

Hi,

       I'm currently very new to National Instrument and LabView Signal Express. What I need to do now is to log the peak-to-peak value of AC voltage to the disk. When I try to log AC voltages, LabView Signal Express only log the ambiguous point along the sine wave instead of  the peak-to-peak value. Is there any way for me to do so? Thanks for helping.

[ThomasC]

Hi,

To take the peak to peak value you will need to add the "Amplitude and Levels" step.  Once this is done you should be viewing the "Step Setup" tab.  Within this tab there are two further tabs, select "Input/Output".  Here there is an option to 'Export peak-peak value'.  If you check this you will now be reading the peak to peak value.  When you go to log the data though make sure that this is selected so that it ends up in your log file.

I hope this has helped, if you still have questions about this please feel free to ask.

Regards,

Thomas Clark

[newbie87]

Hi,

      Thanks for reply. Another new user question is, is it possible for me to plug the wire of AC Voltage to AI+ and another end to AI- to measure the AC Voltage. Cause the waveform the I got is not really follow the input voltage that I supply. Do you have the wiring diagram to connect AC Voltage? I have to test it with the simple one and then expand it. Thanks...

Regards 

[newbie87]

Hi,

      Thanks for reply. Another new user question is, is it possible for me to plug the wire of AC Voltage to AI+ and another end to AI- to measure the AC Voltage. Cause the waveform the I got is not really follow the input voltage that I supply. Do you have the wiring diagram to connect AC Voltage? I have to test it with the simple one and then expand it. Thanks...

Regards 

[ThomasC]

Hi,

For me to answer that question I will need to know a little more about your hardwear setup.  What NI device are you using the sample the data?  What is the supply coming from?  What kind of voltage range are you looking at?

Regards,

Thomas Clark

[newbie87]

Hi, Thomas

Thanks for reply. I'm using NI USB 6008. The supply come from a battery source which I already convert it to AC voltage. Voltage range is less than 10V. Actually, I'm measuring the earth resistivity, with a known resistor and voltage, I can calculate the current. As I'm measuring the earth resistivity from a point to another point, is it possible for me to log each data at a single point in the same log. Another question is, can I measure the earth resistvity with NI USB 6008?

Thank you.

Regards

[ThomasC]

Hi,

To use your USB-6008 to measure the AC voltage you will need to set the input mode to differential and wire into AI0 and AI4.  You can see this by clicking on the connection diagram tab within signal express.

You can also use your USB-6008 to measure resistance, simply set up a new analogue input task as resistance and view the connection diagram as mentioned above for the correct wiring diagram.

Regards,

Thomas Clark 

[newbie87]

Hi,

Thanks again for the reply. Can I know what is the different between Single Ended and Differential?

I don't really understand the circuit work. Is it the circuit I supply with a known voltage and I place the unknown resistor to measure its resistance?

Regards