I have an interesting story to share with you guys and I am curious if anyone else has encountered this.

My daughter (3 years old) has a medical condition that requires the use of a valve implanted in her lumbar region to expel excess spinal fluid from her spinal cavity to her stomach. The valve is adjustable via a electro-magnet at the doctors office. The valve can adjust from releasing a small amount of fluid to a very large amount.

The valve was installed about twelve months ago and for the first 6 months we had no issues. Coincidentally (possibly) we began having problems with the valve shortly after taking delivery of our new Camry Hybrid. The valve seems to magically shift almost 330 degrees out from the lowest setting to the highest setting. I have spoken with the valve manufacturer and they assure me this is not possible without the presence of a relatively strong magnetic field (about 80 gauss). I have seen a CAD of the valve and agree that this is probably correct.

now for the interesting part. My daughter sits in a car seat in the center of the back seat. I presume this is in close proximity to the battery pack and high voltage cables running to the traction motor. Given the nature of the electric pulse required to power the traction motor i am beginning to think it is highly likely that this is the source of the magnetic field. what do you guys think?

Has anyone else ever run across a hybrid interfering with a medical device? The valve manufacturer is sending over a gauss meter so we can run some tests as well as performing their own independent test.

any input is greatly appreciated!

Brian

One other thing I forgot to mention is that we have already audited her environment for anything with a gauss measurement around 80. We removed all magnets and most household appliances don't create that strong of a field

Beckel — The two high-voltage cables (one for the '+' and one for the '-' side of the NiMH battery) run right next to each other from the rear to the front of the car. Since their currents are equal but of opposite direction (because the high-voltage system is electrically isolated with respect to chassis ground for safety reasons), this means that their magnetic fields almost exactly cancel everywhere except very close to the wires — that is, close relative to the spacing between the two wires. This is done both to reduce the external magnetic field and also to reduce the inductance of this loop (they are related to each other). I can't imagine that there is any significant magnetic field from this source.

Stan

Stan,

thanks for the reply. That makes sense. I figured there was no "shielding per say except via a semi twisted pair arrangement.

Is it possible the cables are actually separated near the rear of the back seat and don't come together until close to the chassis? Is it possible the cables run very close to the back seat trunk divide?

Thanks!

Beckel — The cables are close together all the way. I think there's a better diagram somewhere, but this one will do. See page MO-10 of the attached excerpt from the New Car Features Guide.

Stan

Attached Images

MO-10to17.pdf (181.3 KB, 39 views)

See pages 22 and 32 of the TCH owner's manual. Toyota recommends that people with implanted pacemakers and cardiac defibrillators keep a reasonable distance between themselves and the "Smart Key" antennas because the operation of those devices may be affected by the radio waves. They go on to state that users of any electrical medical device should consult with the manufacture to see if radio waves could affect it's operation. I have no idea whether radio waves could interfere with the operation of the valve, but I thought I would bring this to your attention. On page 10 Toyota states the high voltage parts and cables on the TCH emit approximately the same amount of electomagnetic waves as a conventional gasoline powered vehicle. Hope you find out what the problem is. I wish you and your daughter well.

Beckel — Here's some more information on the high-voltage cables from the New Car Features Guide. See page TH-35 in the attached file. I suspect that your daughter's valve may simply be physically vibrating to a different setting. Perhaps the valve mechanism is loose.

peapod1 — I don't think that electromagnetic radiation is a possible cause of the problem here. I also believe that the disclaimer in the Toyota Owner's Manual is there simply for legal reasons, and that the risk of any interference with medical devices from any TCH electromagnetic radiation is negligible.

Stan

Attached Images

TH-19to35.pdf (312.1 KB, 8 views)

I would tend to agree that it is unlikely that passengers are exposed to high enough magnetic field inside Camry to affect anything, the meter will prove it either way, but I did read stories that even Ipod can interfere with pacemakers, when held close to it, but I'm not sure if it was magnetic field, radio frequency or some other type of interference responsible for it.
Here is the link http://www.newsfactor.com/news/Pacem...d=023001BY3XS8
If iPod can do it, then TCH has enough electronics and computers to also be suspect.
Either way please post the follow up.

Ok...received the Gauss meter and started doing some probing. According to the device manufacturer a Gauss reading of greater than 80 is enough to begin affecting the valve settings. I was only able to test the vehicle with ignition on but stationary. In that mode I probed about and did not get any where near an 80 Gauss reading. My next step is to have my wife drive the vehicle and probe around.

Interestingly, we also probed the environment around the house and found very few items with a Gauss reading even over 20. There was however one device, my wife and my Blackberry 8800's that both had a Gauss reading over 150! We need to test other cell phones to determine if it is just the Blackberry or if all cell phone have that high of a reading.

More to come....


Thanks for all the help.

Brian

Beckel — I think you're probably measuring the external magnetic field of the loudspeaker magnet when you test near a portable telephone of any type. (Try near your hi-fi loudspeakers or headphones.) This is not unusual or unexpected. They probably aren't magnetically shielded.

Stan