Impedance Clamp Meter

Watch this project on GitHub

A brief introduction to ICM:

ICM is "just" an impedance-measuring device, which is capable of measuring impedance In-Circuit and in each conducting path (branch) independently.

Easier impedance measurements:

We will start with a discussion of the benefits of this method of impedance measurement.

Using an ICM the user is capable of measuring the impedance of a single branch of the circuit when many branches are connected in parallel. Let's consider the circuit below:

In order to measure the impedance in the branch where R1 resides we would have to disconnect at least one of its nodes from that circuit if we consider the use of the usual multimeter. The situation is different if we use the ICM - no disconnections are required for the measurement of the impedance of R1, R2, or R3! We will have to put a clamp on top of the branch of interest and supply the circuit as it is shown on the diagram above. Yes, you heard it right, in order to make a measurement we would need to supply the circuit and that is the major downside of such a method (we will discuss disadvantages later on).

How does it work (brief):

The main physical principle used in the ICM is Ampère's circuital law. By measuring a magnetic field around the conductor we are able to determine the magnitude of the current flowing through it. Next, by knowing the magnitude of the voltage at the ends of this conductor we now can calculate Impedance between nodes with simple Ohm's law.

How does it work (deep dive):

The main problem in the idea described above is NOISE. The naive approach with direct measurement of the magnitude of a magnetic field in the conductor by a clamp, without a major signal processing phase, would give a resolution of around 1kOhm.

Implementation: