(1) Direct reading method
Measurement of steel Tape 0 scale alignment of the starting point of measurement, the appropriate tensile force (pull the strength of steel tape to identify the pull or the calibration of the pull on the ruler, measured by spring balance), directly read the measurement of the end point of the corresponding ruler scale.
(2) Indirect reading method
In some parts of the steel tape can not be directly used, ruler or square, so that the 0 scale alignment of the measurement point, the ruler body and the direction of measurement, the use of steel tape to the ruler or square on a whole scale of the distance, redundency measured by reading method.
(3) Some errors in measuring steel tape
The more accurate steel tape is manufactured and used for a period of time and must be calibrated to indicate the temperature, tensile strength and length of the test. The length of the mark on the ruler is nominal length, and the difference between the actual length and the δl is called the ruler length correction, and the ruler changes with different pulling force. To avoid this change, a steel tape measure is required to be marked with a pull on the ruler.
The length of the steel tape is changed at different temperatures, so the function of the temperature T as the variable must be used to denote the length of the ruler, which is the formula of the length of the ruler.
Lt=l+δl+α L (t-t0)
The actual length of the measuring tape of the LT steel in the type of temperature T;
L Steel tape nominal length;
Δl length correction number, namely the difference between the actual and nominal length of the steel tape measure at the temperature t0;
Coefficient of thermal expansion of alpha steel tape;
T0 Steel Tape test when the temperature; T steel Tape is used when the temperature.