The situation leading to the question

In the Quick Tips #8 // Precision Helping Hands YouTube Video, a "helping hands" with various names such as "Magnetic Base Adjustable Metal Test Indicator Holder" is used with oscilloscope probes on a breadboard circuit, similar to this:

Magnetic Base Adjustable Metal Test Indicator Holder

I am planning on using a separate one of those holders for each oscilloscope probe with my own breadboard (a total of 4 probes for the 4-channel oscilloscope). But, for convenience of quickly rearranging these holders all around the breadboard, I am considering mounting both the breadboard and the holders with their magnetic bases all on top of some plate steel (needs to ferromagnetic for the magnetic bases to clamp down onto, so cannot be aluminum) from the local big box hardware store. I reason that the steel plate needs to be just large enough to move the mag bases around for clamping down, and just thick enough to avoid the "lever arms" of the base bending up the steel (can't use the 22-gauge el cheapo stuff from the store for this; gotta have something like 1/8" thick steel I believe).

The question

Will this setup shown above cause electromagnetic interference (or actual improvements to isolation against such interference), on the circuit under test, or surrounding equipment such as cables (I doubt the cables will be affected if they have proper shielding), leading to distortion or other artifacts at the oscilloscope?

I'm considering the following possible contributions:

  1. Metal in the arms (probably mostly aluminum but not sure).
  2. Metal in the magnetic bases.
  3. Magnetic fields emanating from the magnetic bases themselves.
  4. Metal in the plate steel.

Extra credit (can we do that in SE??) goes to anyone who can identify how the dimensions (length, width, and thickness) of the plate steel I use as the base for this setup affects the readings.

Oscilloscope is one of the Rigol 4-channel scopes. The scope is not owned by me, so if the specific make/model of scope is relevant, add a comment and I'll update this question with that detail. All scope probes are set to 10x setting.

The circuit under test is a op-amp based circuit similar to the one given by Pulsing Led for Competition - Elektor LABS and thus is not at all a high-frequency circuit. So, my naive bias here is "No, it ain't gonna matter, so go for it!"


1 Answer 1


A current can be induced in a wire by a time-varying magnetic field. If the field itself is not time-varying you can also induce a current by moving a wire with respect to the magnetic field.

In your case there appears to be no movement so no current would be induced. Furthermore, if you place the magnets onto a steel base most of the magnetic field will be contained within the gap, if any, between the magnet and the plate so you would need to have wires very close to the magnets to see any effect at all.

The circuit you want to build does not appear to have any components that are themselves influenced by a constant magnetic field, such as Hall effect sensors. (I couldn't see the schematic without registering and I'm not going to do that.)

So, don't worry. Have fun.


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