NI 9223 - current input range

[DatLe]

Hi,

The datasheet at http://sine.ni.com/ds/app/doc/p/id/ds-260/lang/en just talks about the range of voltage to the analog input. I don't see any places else having the information on the limit on current. I would assume that we have a current range for these analog inputs. Could anyone give the document for this?

Thanks

[johnsold · Accepted solution]

The input impedance is >1E9 ohms. From Ohm's Law and the input voltage range of ~10 V you can calculate the input current as <10 pA.

Lynn

[Buechsenschuetz]

The input in question is a true voltage input. Its input resistance is very high and can be supposed to be infinite for most calculations.

So it does not really have a maximum input current. Of course it might be possible to destroy the input circuitry by overcurrent. Also you cannot force more current into an analog input than it actually consumes. The so-called bias current, as mentioned, is in the pA range.

Even if you make the input a part of a circuit with usually high current (let' s say 1 A), the current in a closed loop is always determined by the component with the highest resistance/impedance. Again, since the input resistance is very high, the current in such a circuit would be limited to the input current mentioned. (This is rather theoretical but with an ideal current source the input voltage might exceed the limits. A photomultiplier is close to a ideal current source and the voltage across the input might raise higher than the voltage limit given.)