PSN-L Email List Message

Subject: Steel vs. other materials
From: JimT nyponen@.........
Date: Sun, 25 Jan 2009 11:07:13 -0800

I'm a newbie and have never built seismometer.  I'm wondering why
steel is used so much in seismometer construction when other materials
have much less thermal expansion.  Spruce wood, for example, has about
1/7 the thermal expansion of steel.  Other materials expand even less,
quartz, graphite, some glasses and ceramics, etc.  Some of the
materials with low CTEs (Coefficient of Thermal Expansion) are
expensive (invar, tungsten, polyimide, diamond), but others are
affordable.  Spruce is inexpensive and widely available.  Here are a
couple of sources of graphite rods and other shapes:

Simax glass is cheap and has an extremely low CTE.  I wonder what kind
of seismometer a good glassblower would make?

Jim Turner

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