Electromagnetic wave propagation when blocked by metal

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Discussion Overview

The discussion revolves around the behavior of electromagnetic waves when encountering a flat metal surface, specifically in the context of building a thermal chuck with a Peltier device for measuring very small currents. Participants explore the implications of electromagnetic interference and noise in the setup.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant inquires about the effects of a metal plate on electromagnetic waves, expressing concern about potential interference with measurements from a Peltier device.
  • Another participant suggests that if the frequency of the electromagnetic waves is not too high or too low, the metal surface will reflect most of the intensity while absorbing a small fraction.
  • The original poster questions whether the absorbed electromagnetic energy by the grounded metal plate will be 'drained' to ground and if grounding is necessary.
  • A different participant argues that constant direct current does not produce electromagnetic waves, questioning the initial premise of the inquiry.
  • The original poster raises concerns about potential capacitive noise from the metal-dielectric-metal configuration and asks if grounding all metal plates could help mitigate this issue.
  • One participant responds that the impact of grounding on noise depends on the specific setup and acknowledges that grounding may not eliminate high-frequency noise.

Areas of Agreement / Disagreement

Participants express differing views on the presence of electromagnetic waves in the context of a direct current setup, leading to unresolved questions about the implications of grounding and noise in the proposed configuration.

Contextual Notes

There are uncertainties regarding the specific frequencies involved, the nature of the noise generated by the Peltier element, and the effectiveness of grounding in reducing interference.

Who May Find This Useful

This discussion may be of interest to individuals working on experimental setups involving electromagnetic wave interactions, grounding techniques, and noise reduction in electronic measurements.

vincenttswong
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Dear all,
I am a newbie in electromagnetic wave. Can you educate me, what will happen when an electromagnetic wave is blocked by a piece of flat metal placed in front of it?

My intention is to build a thermal chuck using peltier for to measure femto amps from my device.
I am worried if EMF created from peltier will affect my measurement.

Below is my stack(top-down):
Device under test -> Metal plate(for conductivity) -> ceramic ->metal plate(connect to ground) -> Peltier -> Heatsink

Please feel free to comment if there is any potential problems.

Look forward to hearing suggestion from you.

Thank you


Regards,
Vincent
 
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If the frequency is not too high (below visible light should be fine) or too low (with a wavelength larger than the device), the metallic surface will absorb some small fraction and reflect most of the intensity.
 
mfb,
Thank you for your prompt reply. Instead of PWM, I am using a steady current source. Therefore frequency is not high.
You did mention about absorbance of small fraction of EM wave by the metal plate. Will the absorbed EM by metal plate(connect to ground) be 'drained' to ground? Am I overdoing it by connecting this plate to a clean ground?

Look forward to hearing from you.

Thank you

Regards,
Vincent
 
I don't see where you expect electromagnetic waves at all. Constant, direct current does not lead to the emission of electromagnetic waves.
 
mfb,
Thanks for your prompt response. I was out of town last week and has got no internet access.
Last question I have here:
Will the sanwiched metal-dielectric-metal layer caused capacitive noise? If yes, is there any ways that I can eliminate them? Can I simply ground all metal plates to drain the charges?

Look forward to hearing from you.

Thank you


Regards,
Vincent
 
I think that will depend on details of the setup. Grounding metal plates makes them immune to low frequencies, but you can still have some HF-noise.
I don't know which kind of noise your peltier element generates.
 

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