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On 23 Sep 2002, at 23:03, Jens Vagelpohl wrote: > > That's about .003", if they are Tungsten, it would be a pretty tough > > wire. > they're made of platinum according to my literature Any idea why? Platinum is a LOT weaker than Tungsten in wire form. Perhaps it has something to do with the change in electrical conductivity as a function of temp, which is what this system uses. Most metals increase their resistivity as the temp goes up, and I know that Tungsten does this dramatically, but it may happen at a higher temp than Bosch wanted to operate. Maybe Platinum changes at a lower temp. I finally found RTD (resistance-temperature dependence) data on both W (tungsten) and Pt (platinum.) At least within the 0-100C range W has the stronger response. Pt is much more widely used as a RTD, however, because it is more linear. In this application linearity is irrelevant because the temp is held constant. I think I would have been tempted to use W instead, for the reasons of cost, temp dependence, and strength, but maybe Pt is more inert in air and hence more stable over time. - Jim Adney jadney@vwtype3.org Madison, WI 53711-3054 USA ------------------------------------------------ To unsubscribe, E-mail to: <type3-off@vwtype3.org> For more help, see http://vwtype3.org/list/