* Temperature correction factors for rod extensometers
Posted by on 09 January 2012 03:49 PM
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Temperature correction values for rod extensometers Figure 1. Rod extensometer 1. Introduction The single rod extensometer employs a rod, anchored at one end of a drillhole, passing into a reference tube fixed in the drillhole collar (see Figure1.). Relative movement between the end anchor and the reference tube is measured with either a dial depth gauge or a vibrating wire displacement transducer inserted through the reference tube and registering on to the free end of the rod. Due to the materials used during the manufacturing of the both the rods and the vibrating wire displacement transducers there are individual temperature correction values for the transducers and the extensometer rods. 2. Temperature correction values Below you can find the temperature correction values for the vibrating wire displacement transducers as well as the values for the stainless steel extensometer rods and the fibreglass extensometer rods.
-0.02 x 10 = -0.2mm In this case, the value is then subtracted from the mm reading taken from the resultant vibrating wire rod extensometer reading. A fall in temperature will result in a positive change in linear measurement which can be corrected accordingly.
There are two types of extensometer rods that we provide with our extensometer systems, these are stainless steel and fibreglass
dl = L0 (E^-6 x α) (t1 - t0) where dl = change in length (m, inches) L0 = initial length (m, inches) α = temperature expansion coefficient t0 = initial temperature (oC) t1 = final temperature (oC) If you are using fibreglass rods the formula is: dl = L0 (E^-6 x α) (t1 - t0) where dl = change in length (m, inches) L0 = initial length (m, inches) α = temperature expansion coefficient t0 = initial temperature (oC) t1 = final temperature (oC)
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