A bit of historical info: For several decades the "zero-length" springs of long(ish) period seismometers with large (gt. 5kg) masses were shipped with a stretcher rod on the inside of the coil spring. (These seismometers are too large to be shipped with the mass and spring installed). The length was the working length of the spring, and although it was quite necessary just to get the spring installed, the main reason was to pre-stress the spring to minimize creep after the instrument was installed. The sensors still needed several days to stabilize. Newer VBB leaf-spring designs are "factory aged" before final determination of constants is done. Some are still notorious for needing a "settling in" period of several days to weeks every time they are installed. Regards, Sean-Thomas _____________________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>