Magnets

Well, the scale method is the "standard" way to know differences between magnets. There's also a "pro" way, that is, with a magnetic field meter (Gauss meter). There's a copulpe of chips, 3515 / 3516 from Allegro (no advertising aim) with a direct output reading of 1mV/Gauss and 2.5mV/Gauss respectively. You just need a +5v power supply t ofeed the chip, and a (preferred digital) voltmeter to know the exact magnetic field strength for each magnet. You can even search for the best magnet to be installed into motors to reach maximum torque. These chips usually cost around 10-12€.

Cons: Since magnetic field is very variable, it depends on magnetic conductors around the magnet (case, rails...) and meter window in this case is very small, you have to run several readings to get an average. This problem is not so important with the scale method but you will get small differences depending on magnet position.

Hope this info's not boring anyone.

QUOTE (Fergy @ 16 Apr 2004, 05:39)...Absolute measurements really don't matter if you have a system in place that is consistent - relative measurements are all you need!
Fergy,

Since one of the illegal tricks done in Spain is replacing motor magnets for more powerful ones, people who verify cars need a tool to read an accurate value to be measured anywhere and create a "standard".

They tried to use DS but, as I said before, it's not accurate enough to create a limit value, two different DS magnet meters show different values for the same motor.

Last november Ninco used the scale system to detect illegal motors in the "11th slot-rally de Lloret-Costa Brava", but no one at home can reproduce the same value unless they have exactly the same pieces used on the scale used as "standard".

Of course I agree with the idea that you don't need an absolute magnet meter... unless the race regulation says that "limit value for magnet in the motor is 250Gauss faced to the track", and this happens in Spain.

QUOTE (Fergy @ 16 Apr 2004, 17:38)Nep, I understand the dilemma ...To get accuracy, you need a proper gauss meter, properly calibrated, and good ones can be a bit expensive for most racers....One trick used in HO racing was to specify that the magnets could not pick up a specific metal object ...
Sorry, Fergy, I didn't explain correctly my idea.

I fully agree with you, for anyone a relative measuring is enough. Problem is when regualtions try to normalize this: they measure with one Gauss meter, I use another. With mine, motor is OK but with them motor is illegal. Which one is correct? It's hard -not to say impossible- to create an exact rule for magnets.

Best solution to use DS pocket checker is, IMHO, check first sensor position: it must be flat agaist cover, or even remove cover to keep sensor in contact with the motor/magnet. This way you will get the best, highest value. Of course you can use mechanical systems, but for 90€... well, maybe it's not as expensive as the Kelvin Bench (and Kelvin's system does not measure magnets-and will not do it)