Re : using battery to test acquisition

[DavidL]

Hi all,

I've got a huge noise problem is a tention Differential AI (-10V/+10V 10mA signal) on a PCI6220. It spikes around 0.5V on each of the  2 différent AI couple.

When i test acquisition by connectiong a 1.5v AAA battery there is no more noise (0.2 mV), using the same wires. (I ve tried with and witout an extra resistor)

If asked the sensor manufacturer, but he told me it was not a good way to test acquisition due to lack of impedence.

What do you think of it ?

Is there a possibility of a mass loop ?

Then how can i fix my noises issues ?

Thanks a lot if you can help.

[mehdi.afif]

Hello.

What do you measure when you have a spike of 0.5V?

If you're trying to measure 100mV signal, you have to set a smaller range than +/-10V for your analog input task.

If you source signal is floating (battery), you can connect bias resistors as explained in this document.

http://zone.ni.com/devzone/cda/tut/p/id/3344 (table 1).

I hpe this helps.

best regards

[DavidL]

Your link seems very interesting, unfortunatly i 've got very low "electricity skills". I 'm just a programmer. But i will transfer it to more competent people.

I 've got such spikes aquiring any signals (1.5V battery or all range (-10V/+10V) of a force sensor  behing a charge amplifier.

Thank you Mehdi.