USB-4431 as lock-in amplifier

[eddycur88]

Hi all,

Question regarding hardware for lock-in amplifier.

I need to build lock-in amplifier using one of NI DAQ-cards and LabView software.

Due to the need to move it from one place to another we prefer solution based on notebook and thus USB DAQ-card.

I found this oneUSB-4431, having 4 channels (seems to be working in pseudo-differential input mode, if I am not mistaken), 24-bit resolution, up to 102.4 kS/s sampling rate, delta-sigma ADC and simultaneous sampling mode and +-10V input range - so looking similar to PCI-4472/4471.

But it has smaller dynamic range (100dB instead of 110dB), smaller timebase accuracy, and sample-rate resolution and it seems that it doesn't hav antialiasing configurable filters, etc.

I need it for light-measuring applications with signal levels >10uV and I intend to use low-noise configurable AC/DC pre-amplifier (from Femto company) having gain and bandwidth control in order to amplifier signals before DAQ-card.

Can I use this USB-4431 for this purpose?

It seems to be slightly less good comparing to recommended internal PCI cards like NI 4472(4471), but maybe it is enough good for my application?

If not, which USB DAQ board can you recommend for this purpose?

Thank you in advance,

RG

[Roohcifer]

Hello,

Generally speaking, NI DSA cards (44xx series) have onboard filtering capabilities, low noise floors, delta-sigma ADCs, and other properties that make them conducive to taking high resolution measurements, particularly for sound and vibration signals.  Many also have a wide range of programmable gain settings and AC/DC coupling options, so the external circuitry you proposed may not be necessary.

I would check out our range of DSA cards here:

http://sine.ni.com/nips/cds/view/p/lang/en/nid/10365

Unfortunately, the 4431/2 are the highest performing cards we prodive in the USB form factor.  PCI and PXI options would lower the noise floors and increase max sample speeds greatly.  If you have particular spec questions, I would call 877-387-0015 and ask to get in touch with a sales engineer.

Regards, 

[eddycur88]

Dear David,

Thanks a lot for your answer and suggestions.

Best regards,

RG

[zhm0204]

Hi David R,

We are looking for a USB multifunction card that have 4 AI 24bit and 1 AO. 16bit.

Like a USB 4431 but may work with a external sampling clock (encoder signle).

Do you have one?