Temperature Correction on Crackmeters

The crackmeter working elements are made primarily of steel and stainless steel and are affected by changing temperature to a certain predictable degree. In case of large temperature changes application of temperature correction will improve the accuracy of the measurements. The approximate temperature effect on the gauge is -0.02mm per degree Celsius. Hence for a temperature increase of 10°C a crackmeter will indicate (-0.02 x 10) -0.2mm to the result indicated by the crackmeter reading. A fall in temperature will result in a positive change in linear measurement which can be corrected accordingly. Physical dimensional changes due to temperature in the crackmeter and the structure on which it is mounted are of the order of 10-6mm/m/°C and can be neglected.

For strain gauges installed on concrete with no loads are acting, the thermal concrete strains are given by:

µɛ(thermal) = (T1-T0)xCF1

CF1 represents the coefficient of expansion of concrete. Unless this figure is known, assume a nominal value of +10.4 microstrain/DegC. As assumptions are made for the thermal coefficients of concrete the equation should be considered as a general guide.