Ben W

I've seen in several blogs now where a commenter has stated that the Roadster is like "strapping a bag of cell phones to your head", in terms of the EMF radiation. So I picked up an EMF detector, sensitive in the 30-300Hz range (serendipitously equivalent to 1800 - 18000RPM), and took my Roadster for a spin.

For calibration, the meter shows around 100 milligauss when placed next to my iPhone on a call, in the position my head would be.

In the Roadster, I found that the only place in the cabin with noticeable EMF levels is just above the headrest; the reading peaked there at 50 milligauss (half the strength of a cell phone) for a couple seconds during peak acceleration. While cruising, the EMF reading there was around 3-4 milligauss, and dropped to imperceptible levels throughout the rest of the cabin.

In other words, the kinetic energy of the Roadster is a far greater concern than the electromagnetic energy. Thought some of you might like to know!

-Ben

TEG

Thanks for some real data. I figured those reports were trumped up sensationalism, but I had no way to disprove it myself.

WarpedOne

This post should be made sticky so we have it at hand when someone somewhere starts to spread this FUD again.

Thank you!

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DaveD

I wonder what the measurement would be near a Bluetooth headset that I see so many people wearing around nowadays.

vfx

I wonder what other motorized devices get placed near the body.

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Ben W

Zero. (Unmeasurable.) At least a thousand times less than the cell phone itself. Remember, the cell phone has to broadcast its signal a few kilometers; the bluetooth no more than 10 meters, and broadcasting power increases with the square of distance. My detector wasn't able to pick up any trace of EMF from my Jawbone bluetooth headset.

Ben W

Probably not what you're thinking of, but hair dryers put out at least as much EMF as cell phones.

Those other gadgets -- well, no risk, no reward.

dpeilow

Good idea. Done.

WarpedOne

It looks to me this case was closed a little bit too fast.

According to Wikipeda, variable-frequency drives have something called Carrier Switching Frequency (CSF), a frequency of the current going through the stator windings which is completely different from the frequency of rotating magnetic field in this same stator. This one varies from 0 to 430Hz (at 13.000 rpm of a 4-pole motor).

30-300Hz EMF detector is as such completly inadequate for the job at hand. CSFs are usually in tens of kHz so one should get a detector with suitable range and repeat the measurements.

Not that I'm afaird of EMF, I would just like to have correct results :|

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DRM

A couple of thoughts:
the EMF meter you're using won't be able to detect the (primary) emissions from the car due to its limited bandwidth (300Hz). Main emission frequency will likely be in the >10kHz range due to the PEM module's primary switching frequency (which should be many times higher than the motor's RPM).

Bluetooth runs at 2.4GHz and ~0dBm (1mW). You could not detect it with a 300Hz detector.

Cellular runs at ~900MHz/1.8GHz at +24dBm max, but typically around +18dBm -- less than 100mW.

If a San Diego-based roadster owner wants to stop by Sorrento Valley, I'll volunteer the use of a good Spectrum analyzer to sniff around the car.

Dan.