Using the NI USB-6008 to measure high voltages

[bmihura]

I want to use my NI USB-6008 to measure up to 100 volts. The problem is that its input impedance is only 144k, and I'm afraid that a resistor divider would interfere with that.

I'd like a 10:1 resistor divider, so I'm considering a 1M and 100k resistor, but I'm afraid the current would be so low it would be susceptible to noise.

What's the best way to do this?

[Joe_S]

bmihura,

Thanks for posting. If you are looking to measure up to 100 V with a USB-6008, the short answer is that there really is no good way to do that. The device specifies a ±10 V operating range (±20 V for differential inputs). You can try using a voltage divider and it may reduce the current of the signal significantly, but the 6008 is just not designed to work with voltages that high. There are some other products that we sell, such as the NI 9225, that could handle voltages that high that you could consider using instead of the USB-6008. I hope this helps!

[SnowMule]

Could try a high voltage probe... they come in 10x and 100x flavors... input impedance of the DAQ may present a problem... and it may not. 

[taper]

We do this all the time.  Simple resistor divider on an in-house analog mux/conditioner pcb.  You'll want an active buffer between the divider and the DAQ, see https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z000000P84RSAS&l=en-US for more info.  Between the buffer and maybe some zeners the card will be protected against high inputs.

Having a 10:1 divider will reduce your effective resolution by 10.