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Ben W

2008 Roadster, 2017 M3, 2022 MY
Feb 27, 2009
Santa Barbara, CA
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. :biggrin: Thought some of you might like to know!


Ben W

2008 Roadster, 2017 M3, 2022 MY
Feb 27, 2009
Santa Barbara, CA
I wonder what the measurement would be near a Bluetooth headset that I see so many people wearing around nowadays.

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.


Supreme Premier
Supporting Member
Aug 17, 2006
Slovenia, Europe
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 :|
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.

It's great to see this topic. It seems the EMF concern is one that is not adequately discussed in the EV arena. A week ago, I actually asked Tesla Client Advisor Mike Falcone about this in relation to their Model S. His response:
I've been asked about the safety of the electronics before and I've been told that they generate less radiation than a microwave oven.
So apparently they have made an effort to make sure the EMFs are well within safe levels for the Model S as well. Which, since I'm on the waiting list, is something I'm very happy to hear!


Well-Known Member
May 23, 2008
Winchester, UK
We were trying out a new spectrum analyser in the office recently when someone switched on a microwave on the other side of the room (about 30ft away). It completely swamped the signals from an adjacent phone that we were using to check it with, the background cellular networks and the nearby wifi access point which were also showing up. Something for the campaigners (and people working in kitchens) to consider.

But like Tesla Dave says, you wouldn't sit near a microwave for a couple of hours, so perhaps they need to get a better comparison.
@dpeilow: Maybe the microwave has faulty seals? A new microwave with good seals should have very little microwave leakage - but the EMFs from its transformer is another matter!

Come to think of it, I remember at the Menlo Park event when Elon got too close to the car it caused some bad static in his microphone. (Anyone else noticed that?)
But then it is just a prototype, and they are aware of their customers' concerns regarding EMFs - so hopefully this won't be a problem in the production model.
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