How does mullti-tone 2 wire vs 4 wire LCR inductance measurements....

[LVocho]

What's the diference between having a DMM to measure resistance and a LCR? I've seen many ATE's with both equipments, a DMM and LCR, the first one it is used to measure resistance (2 or 4 wire method) and the other one it is used to measure inductance or capacitance (always in 4 wire method). Why don't use the same device to do both measurements? Can I use a NI PXI7042 in order to get resistance and inductance from a DUT? Does multi-tone technique eliminates in someway the use of 4-wire method?

 has something to do with the DMM voltage-frecuency delivery capacity?

Any further explanations or comments will be most welcome!

[Tania_Lozoya]

Hi LVocho,

You can use the PXI-4072 to measure resistance and inductance of an UUT.

If I am correct, the traditional way to measure inductance and capacitance technique uses a sine wave and a precision synchronous detector.

The PXI-4072 DMM uses a multi-tone signal, basically it generates a very precise square wave (in frequency domain has many frequency contents) and it’s harmonically limited.  You can find more details in the NI Digital Multimeters Help File:

http://digital.ni.com/manuals.nsf/websearch/9D5E03DA68E9F6C9862572C1005B0ABB

And in the Getting Started Guide NI Digital Multimeters:

http://digital.ni.com/manuals.nsf/websearch/E7CCD5EDCF3980C3862572C1005B563F

Also you will find very useful information in this page:

http://zone.ni.com/devzone/cda/tut/p/id/3297

Specifically look at:                         

http://zone.ni.com/devzone/cda/tut/p/id/3078

http://zone.ni.com/devzone/cda/tut/p/id/3713

Please let me know if you need more information.

Tania Lozoya | National Instruments | Mexico

[LVocho]

Thanks Tanya,

    I've red the DMM tutorial and pages you have made reference. I still have doubts regarding the test frecuency ranges. What if I need to measure the UUT inductance with certain mH at a specific frecuency? Multi-tone technique supplies frecuency according to the range selected.

Thanks!

[Tania_Lozoya]

Hi LVocho,

Unless you can use one of the frequencies that the specs of the PXI-4072 have to measure current, you cannot use this method to measure the inductance of the UUT. The PXI-4072 is more accurate and is a less expensive approach. However, you can create a LC reader with any of our DMMs. Use a NI PXI (or NI PCI) device to generate a single tone sine waveform and measure the response of the UUT. By software you can compare the current and voltage of the UUT response, and since it has inductance the voltage will lead the current, and you can measure the phase between those two signals and get the inductance value: the traditional method to measure inductance. You will need to use two DMMs to get the signals synchronized.  

Please let me know if you need more information.

Tania Lozoya | National Instruments | Mexico

Mensaje editado por Tania Lozoya

[LVocho]

And we end up with the 4-wire method. I just wanted to know why I haven't seen a 4 wire inductance measurement technique on a NI DMM. Actually I have an application in which I need to measure from 800 to 1300mH @ 1KHz. Wouldn't be easier to have asked this since the beggining??

Thanks Tanya!

[Tania_Lozoya]

Hi LVocho,

You would have to use two DMM’s for this operation, because we can’t make simultaneous measurements of voltage and current with one device.  Please let me know if you wish to talk to a Technical Representative, so that we can give you the options you have for your application.

Sorry for the delay in the response I was out of the office.

Tania Lozoya | National Instruments | México