As you can see, stainless steel has a negligible coefficient. So, I feel vindicated. Stainless steel is exotic by the way. It is just mass produced and used for construction, thus making it pretty cheap.Richard
Wednesday, August 19, 2009
Temperature Coefficient for Electrical Resistivity
I remember telling someone in a forum about using stainless steel bolts as a shunt for use as a cheap current measurement. Someone else said that shunts are made with exotic (aka expensive) materials with very low thermal coefficients of resistance. I found this chart not too long ago and thought I would post it.
As you can see, stainless steel has a negligible coefficient. So, I feel vindicated. Stainless steel is exotic by the way. It is just mass produced and used for construction, thus making it pretty cheap.
Richard
As you can see, stainless steel has a negligible coefficient. So, I feel vindicated. Stainless steel is exotic by the way. It is just mass produced and used for construction, thus making it pretty cheap.Richard
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Good blog by the way. A detail that will help if you have not already caught it: The above chart is thermal resistivity, not thermal coefficient of electrical resistivity. Aluminum resistance is 2.82 x10 (-8) ohm/meter (don't care at the moment) and the thermal coefficient of resistivity is 0.0039 /deg. K. The simple math is 0.0039 x delta T x 2.82. But the easy thing is to consider the 0.0039 as a variation on percent change. So we look at the coefficient of resistivity of the neat alloy Manganin - 0.000002 or about 2000 times better than aluminum or many other metals. 18-8 Stainless steel has a Tcoef of 0.00094, 4 x better than many metals but not great if the temperature varies too much. Decent shunts are available cheap on ebay.
ReplyDeleteNeat stuff you do. Much appreciated.
I retract my misinterpretation of your choice of graphs. Too many distractions. I need a shed or office. But real shunts are still better for tight tolerance measurements over wide temperatures. Feel free to dump both comments :)
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