Increasing DAQ impedence to measure current.

[ASheldon]

I wish to increase the impedance of my circuit which incorporates the DAQ. I understand that the impedance is 144kOhms, is it possible to place a 10MOhm resistor is series and a 100kOhm in parallel? I wish to measure currents of the order 10nanoAmps to 1microAmp where the voltage will exceed 20Volts if a spike occurs.

[TheWay]

Hi there,

If you let me know what specific DAQ device you are using I can look into this issue further.

Regards,

Way S.

NI UK Applications Engineer

[ASheldon]

Thank you for your reply,

I have the NI USB-6008 12-Bit, 10kS/s Low-cost Multifunction DAQ.

Andrew Sheldon

[TheWay]

Hi Andrew,

The USB 6008 can only only measure voltages up to +-10 V with respect to ground on its analog inputs in single-ended mode. In differential mode however, you can measure up to +-20V in the +-20V range.  You can add any external circuitry outside of the 6008 to condition the input signals. Refer to the manual for more specifications on the 6008:

http://www.ni.com/pdf/manuals/371303h.pdf

Way S.

[ASheldon]

Thank you very much for your help.

Andrew Sheldon