measuring resistance

[tamureu]

I was wondering if there was a way in LabVIEW to have a graph constantly showing measured resistance through a metal.

[Taki1999]

Yes but the actual method will depend on what you're using to measure resistance.

You should probably start by describing how you're measuring resistance and which devices you're using.

[tamureu]

That's the problem. I need a device I can connect to the DAQ board that measures current through a piece of metal.

[Taki1999]

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@tamureu wrote:

That's the problem. I need a device I can connect to the DAQ board that measures current through a piece of metal.

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That's a hardware problem, not a LabVIEW one. Any accuracy or resolution requirements? Measuring in the 1-10 amp range has very different requirements than trying to measure in the mA with microamp resolution.

First decide how you're going to measure your quantity of interest. From there, the display should be trivial.

Also, what sort of DAQ board are you using?

[crossrulz]

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@tamureu wrote:

That's the problem. I need a device I can connect to the DAQ board that measures current through a piece of metal.

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Just use a DMM and set it to measure resistance.  If you want to use PXI, the PXI-4070 works really well.

[tamureu]

Are there any cheaper options?

[johnsold]

Probably. But you may need some external circuitry.

What is the range of resistances you want to measure?  What are the requirements for accuracy, resolution, and speed? What are the limits on voltage or current excitation? Is the "metal" which is being measured connected to ground or any other electrical circuit?

Lynn

[Henrik_Volkers]

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@tamureu wrote:

Are there any cheaper options?

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Yes, your soundcard 🙂

Line out drives the unknown and a known resistor in series as a voltage devider, left and rigth channel measure feeding AC voltage and the divided voltage ....   need some calibration and don't work for all ranges 😉   More sophisticated solutions add some OPs to buffer the voltages.

What is the resistor range?

How exact do need to measure?

Traceable?

[Hooovahh]

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@tamureu wrote:

Are there any cheaper options?

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Oh yeah, but they don't come with the support, reliability, and features of NI hardware.

Here is a portable DMM with an RS-232 interface for $36.

http://www.amazon.com/TekPower-TP4000ZC-RS232-Interaced-Ranging-Multimeter/dp/B000OPDFLM/ref=cm_cr_p...

With it you can measure current, voltage, resistance, capacitance, AC/DC, and a few others.  It has an RS-232 interface so you can bascially read what the display is showing, in LabVIEW.  If this runs long term you'll want to disable the auto-off feature, and provide a constant source of power probably from an outlet.  And it just so happens that someone super nice wrote drivers for you.

http://forums.ni.com/t5/Instrument-Control-GPIB-Serial/Cheapest-RS232-Serial-DMM-with-LabVIEW-instru...

All you need is a spare COM port, or a USB to RS-232 adapter.