my project is to measure ac voltage and current using lab view.

[ChrissyC]

Hi,

There are numerous threads here on the NI forums about measuring AC voltatges and currents. Here is one of the first ones I looked at, and a snippet from NI help

The myDAQ will be able to measure the voltages if you choose to use the shunt method, or a current clamp. 

-CC

[Ranjeet_Singh]

There is manual of mydaq. Why dont you read that. That will tell you whether that suits your application or not ?

[Hooovahh]

If you are talking about 3 phase things get a little more complicated.  One setup I've seen but have yet to try out is this USB cDAQ solution.

http://sine.ni.com/nips/cds/view/p/lang/en/nid/208111

It can read the 3 phase current and voltage simultaniously up to 300VRMS, and 5ARMS.  Given these 6 measurements you can calulate phase shift, power factor correction, and a whole bunch of stuff.

[NIquist]

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@321hanan wrote:

But I need it confirm that my task can be done by that device because it is very costly and I m not a professionalist.

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As Ranjeet has said, the MyDAQ is a neat little multi-purpose device from NI which means it will interface with LabVIEW easily.  We cannot answer ANY questions about whether it will work for YOUR task because you haven't told us what YOU'RE doing.  The myDAQ can measure currents up to 1 AMP and voltages up to 20VDC.  Now, what are YOU needing to measure???  There's no point aksing for more advice if you don't tell us that...

[321hanan]

I want to  measure both dc and ac voltage(ac upto 230v or more) and ac current upto 7 A. If i could do so then further I want to measure p.f and ac power.

[NIquist]

Ouch.  YOu're going to need to create your own front end to measure signals at that power level.  The basic DAQ cards are all designed to measure low-level signals.  You could use one of the NI-DMM devices but they are FAR more expensive and probably overkill for your app. 

Another option to consider is to use a standard DMM that you might already have and interface it to LabVIEW through GPIB, USB or serial connections. 

[djroseman · Accepted solution]

You could use current and voltage hall effect transducers to bring the input signal down to the range of your DAQ device - you could get up to 1000Vrms and 1000Arms detection and bring it down to 4-20mA or +/-10V.  As for LV tools, you can easily get PF and power measurements by using the Electrical Power Measurement Toolkit, the basic measurements are now free. 

[321hanan]

In This regard which daq device will be better for the purpose.

[djroseman]

If you are using current and voltage transducers, you can use pretty much any general purpose analogue input DAQ for PXI or cDAQ, or whatever you like.  If you need to look at the phase relationships between acquired signals, then you will need a simultaneous DAQ with multiple ADC's such as the PXI-6143.

Dave