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Using input impedance to measure current

Posted on Wednesday, August 19th, 2015 in measurement by DP

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Using input impedance to measure current, see the detailed blog post here from Sigzig:

Input impedance on measurement equipment is usually kept as high as it can in an effort to prevent loading down the signals the equipment is measuring. For example most general purpose digital multimeters aim for an input impedance of at least 1M ohm. The Zig-4 has a lower input impedance of 330k ohms but this is still high enough for many/most situations. That being said it is still important to understand input impedance and its affect on your measurements.
In this post I thought it would be fun to actually take advantage of the 330k input impedance of the Zig-4 as a sort of low current sensing.
The goal: To see if we can use the Zig-4 to detect a change in current in the very low nA range.

This entry was posted on Wednesday, August 19th, 2015 at 11:39 pm and is filed under measurement. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.

2 Responses to “Using input impedance to measure current”

  1. Drone says:

    “Input impedance on measurement equipment is usually kept as high as it can in an effort to prevent loading down the signals the equipment is measuring.”

    Maybe in your alternate universe. Here back on Earth for example, my Vector Network Analyzer’s input impedance is matched to the desired 50+j0 Ohm system characteristic Impedance.

  2. Realwork says:

    Maybe it should have said “When you are not worried about impedance matching” Also we already know he was not talking about power transfer out of the equipment.

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