Low voltage measuring

Hello
would measure a voltage in the order of 8.4 mVrms +/- 7% using the ni PCI-6143 card. is that this choice will meet my needs?
is that twisted wires are required to do this kind of measurement ?
Thanks

Hello Nebyl,
First of all i'll suggest you to answer in french (as we're here in the french part of the forums). If you accidentally went to the wrong part of NI Forums, i'll ask you to post here (if my following answer doesn't answer your first question) : http://forums.ni.com/t5/Multifunction-DAQ/bd-p/250
Pour résumer, vous auriez besoin de faire des mesures autour de 8 mVrms (+/-7%) avec la NI-6143, et vous hésitez à vous procurer un cable torsadé.
La carte pourra sans aucun doute faire la mesure. Au niveau du bruit, votre carte NI-6143 possède 8 entrées différentielles, ce qui réduira déjà le bruit par rapport à une masse référencée. Ensuite, le besoin d'un câble de réjection de bruit naîtra probablement de vos conditions de mesure. Si vous réalisez vos mesures dans un environnement relativement perturbé par un champ EM, ou que votre capteur/générateur de signal est loin de votre acquisition (longueur de cable >2 mètres), vous aurez un bruit d'autant plus grand, et dans ce cas un câble torsadé sera de mise.
La carte NI6143 possède des accessoires adaptés à ce genre de mesure : http://www.ni.com/pdf/products/us/04_3512_301_101d.pdf
Enfin, je vous suggérerai de faire quelques tests sans câble torsadé, et voir si la mesure est satisfaisante.
Eric M. - Application Engineering Specialist
Certified LabVIEW Architect
Certified LabWindows™/CVI Developer

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Hi,
I am using PCI 6025E to control load bank and to measure voltage, current and frequency of a generator.
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If you have a sine generator (15Hz migth be hard for the soundcard ) you can do a calibration of your transformer.
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Greetings from Germany
Henrik
LV since v3.1
“ground” is a convenient fantasy
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小木虫
Solved!
Go to Solution.

I used a setup shown in Fig. 1 to measure potentials of 121 electrodes (120 zinc wire and 1 iron wire, 1mm in diameter, embedded in epoxy resin, each electrode allowed one surface exposed) in NaCl solution against a reference electrode (with a constant potential). The HI line of DMM was connected to r0 and the LO line was connected to the reference electrode.
Fig.1
These 121 electrodes were connected to the terminal of 2535 with 5 pin Ribbon cables, each of which has 25 lines.Generally, the potential of Zn is about -1.1V and -0.5-0.6V of Fe in NaCl solution. I used the niswitch DMM switch synchronous scanning.vi, sample of LV8.5 to measure these potentials. But I found that the potential of Fe was about -1V, which was similar to that of Zn. This did not occur when PXI 2532 was used. I used a portable DMM to measure the potential of Fe in the 121 electrodes and the results was -0.56V whether I run the sample vi or not. Then I suspected that the switch bring some effects on the measurement.To clarify this problem, I connected a Fe wire to c135 channel (as shown in Fig.1) and measure the influence of other 121 electrodes on the potential measurement of the c135. 1. I did not connect pin Ribbon cables to the switch and used the DMM waveform demo to express the potential of the c135 channel evolution. I opened the soft front panel of the switch and made the c135 connect to r0, which was connected to the HI line of the 4071. When the demo was run, the potential was constant and about -0.56V, as shown in Fig. 2.
Fig.2
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Fig.3
3. When two pin Ribbon cables (50 zinc wire connected to switch terminal) were connected to the switch, similar result was obtained, which was shown in Fig 4.
Fig.4
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Fig.5 (a)
Fig.5 (b)
Fig.5 (c)
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Attachments:
problem about measurement.pdf ‏113 KB

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Henrik
LV since v3.1
“ground” is a convenient fantasy
'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'

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atze

atze
Do you do anything else that uses both processors? I am just curious as to why only with Retrospect.
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Low voltage measuring

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