Terms/Explanations General Force Strain Strain STRAIN-MATE Axial Load Strain l ε= ∆ l Strain is defined as the non-dimensional ratio of length change / initial length. Microstrain is often used as strain unit. 1 microstrain [µε] = 10 -6 Mechanical strain µm m = 1 m m The mechanical strain results of the strain of the E-modulus of the material respectively of the force per area. s = ε *E (in the flexible span) MaterialE-modulus (typical) bzw. s = F/(E*A) Steel 210 kN/mm2 Aluminium 70.5 kN/mm2 Example: 250 µm/m strain equals to a mechanical strain of 52,2 N/mm2 respectively (52,5 MPa) on steel. Output range The output voltage is the difference between the output signal at zero load and the output signal at nominal load. Nominal characteristic value Specified output signal at nominal load (nom. output voltage). Characteristic value Actual (measured) output range. Measuring range Load range in which the specified errors are not exceeded. Hysteresis Hysteresis signifies the hysteresis error Fh. ∆Smax is the largest difference between the increasing and decreasing calibration curve up to the nominal load. Hysteresis is expressed in % of full scale. ∆Smax FN Δ S max Measuring range 11.2 www.baumer.com Output signal at nominal load = Output signal Fh L N (Nominal load) Terms/Explanations General Force Strain Strain STRAIN-MATE Axial Load The characteristic curve deviation signifies the maximum deviation of the calibration curve to the specified straight line. The specified straight line passes through the origin. The end point results from the origin + nominal output voltage. The characteristic curve deviation contains hysteresis, linearity error, repeatability and deviation of real to nominal output voltage. Δ S max Measuring range L N (Nominal load) Linearity error FL is the largest difference ∆Smax between the increasing calibration curve and the straight line through the origin with slope CL. CL is selected such that ∆Smax is minimized. The linearity is expressed in % of full scale. FL = ∆Smax CL · LN Δ S max Output signal Linearity Output signal at nominal load ∆Smax FS Output signal FCom = Full scale Characteristic curve deviation Measuring range L N (Nominal load) 11 www.baumer.com 11.3 Terms/Explanations General Force Strain Strain STRAIN-MATE Axial Load Micro strain [µε] See strain. Zero, bridge balance Generally all S/G bridges exhibit an initial offset which can be tared by different means. After the installation the offset of STRAIN MATETM sensors may be quiet large due to the press-on technique. Baumer amplifiers and display instruments are equipped with a reset circuit which allows fast and convenient zeroing over a large range. For static applications, amplifiers with zero balance potentiometers or digital taring are used. Repeatability The difference in reference to the characteristic value between the max. and the min. display value of equal measuring points in case of repeatation of identical load cycles. TestOUT RC TEST + OUT + SIGNAL OUT RC RESET The non-tared signal is available at the output TestOUT. To prevent saturation of subsequent stages, TestOUT should ideally read between -2 V and +2 V when the sensor is installed and no load is applied. During operation this value may then be between -5 V and +5 V. The TestOUT output can furthermore be used to check the measuring chain. In case of an open bridge circut, TestOUT goes into saturation. Output signal TC of zero signal T +1 K FS T Measuring range L N (Nominal load) Output signal TC of output range T +1 K FS T Measuring range The maximum temperature coefficient (TC) of the zero signal is the largest variation of the zero signal which occurs during a change in temperature by 1 Kelvin. It is expressed in percent of full-scale per Kelvin. The largest temperature coefficient (TC) of output range is the largest variation in output range which occurs during a change in temperature by 1 Kelvin. It is expressed in percent of FS*) per Kelvin. L N (Nominal load) *) FS = Fullscale of output range 11.4 www.baumer.com