Reccomend me an amplifier?

[dsafdsafa]

I searched the NI catalogs for some voltage amplifiers, but either they do not offer, either I simply could not find them.
I need to measure small voltages (less than 1mV). 
I intend to use the amplifier to boost the voltage, so I can measure it with ±10V ranged DAQs.
Probably a 500 or 1000 gain will be okay.
Could someone reccommend me something?

[Buechsenschuetz]

NI seems not to be specialised in pure instrumentation equipment. Maybe you will find the device you need in catalogues from companies specialised in making general purpose instrumentation equipment, like Omega (omega.com). A quick search revealed this one:    http://www.omega.com/pptst/OMNI-AMPIIA.html, if a factor of 100 is sufficient. Anyhow, measuring voltages in the sub-mV range requires very careful setup of grounding, shielding and power supply issues to avoid noise. You did not tell us which bandwidth you need but it is always a good idea to limit the bandwidth as far as possible. Most DAQ boards offer digital filtering but you always should integrate a hardware filter circuit at the input of the DAQ board. 

[EBL]

Many NI products include enough gain to make measurements at very low levels, so that external amplifiers are not required (having internal amplifiers also means you don't have to manually calibrate your measurement system). If you can give us an idea of what kinds of signals you'd like to measure (e.g. what frequencies, levels), and how much dynamic range (or noise performance) you need, we might be able to suggest a product that already has enough amplification built-in.

Hope this helps,

Ed

[dsafdsafa]

My aim is to measure active resistance (several hundred microohm), therefore DC current will be used (10 to 50 Amp). Current measurement is okay, but voltage drop is quite small.
We have already some DAQs, which are used for other purposes, so buying additional hardware is not a prefferable option.
At least now I know that I shall not seek amplifiers from NI. I'll check the omega.com, in case they have representatives in my country.

[Buechsenschuetz]

You will hardly find any DAQ suitable for measuring voltages in the mV- or sub-mV range. The reference voltage of all DAQs I know is in the 1 to 5V range which also sets the full scale sensitivity. Since DAQ boards usually are designed as general purpose devices most manufacturers do not integrate preamplifiers on their boards, in almost any case you have to use external hardware for very low signals. 

[Henrik_Volkers]

Please provide more specs:

Frequency range

Noise

Linearity

Offset

Drift ...

Z_in 

Robustness (Lab or field)

Prefered power source (Main or AD card, 5 or +-15/12 or ???)

Just to name some...  

Another spec is max$$ 😉

Sometimes a simple OP (evaluation board) from NS,TI or Linear can do the job.. or

5B Modules  (look if you can adapt TC amps)

Next are aktive probes (Tek, Agilent .... )

or scientific amps from Preston (they will build/sell everything you want ...   to pay!)

[EBL]

There are indeed NI boards that can handle your measurements. Let me assume a typical scenario in your case: suppose you have 200 microohms and excite it with 20 A. That would produce 4 mA. If you used, for example, a 6030E or a 6032E, your accuracy with the +/- 100 mV range would be 0.0461% of reading, plus 12.7 uV offset, plus 1.8 uV of quantization error when noise is averaged away. For 4 mV, that comes to 16.3 uV, or 0.4% error. I don't know what specs you're shooting for, but it will be a bit of a challenge to find an external amplifier that will give you a total system accuracy as good as that.

You might also look at one of the DMM boards, such as the 4065. On the 100 mV range, that board will read a 4 mV signal with an accuracy of better than 3.86 uV.

Hope this helps,

Ed

[dsafdsafa · Accepted solution]

Thanks to all of you! Now, when I know NI does not manufacture such amplifiers I found another company to manufacture me one. 

[Candy Yu]

deae sir, you can check the website:www.szsunyuan.com.maybe you can find goods that you need. Candy