The force measurement of tensile strength testing machine is measured by force sensor, amplifier and data processing system, and the most commonly used force sensor is strain gage sensor.
The so-called strain gage sensor, is composed of strain gauges, elastic elements and some accessories (compensation components, shields, wiring sockets, loading parts), can be a certain amount of mechanical energy into the output of the device. Strain gauges of tensile and pressure sensors at home and abroad a wide range of types, including cylindrical force sensor, spoke force sensor, s double-hole sensor, cross-beam type sensor and so on. From the mechanics of materials, it is found that under the condition of small deformation, the strain ε of a certain point of a elastic element is proportional to the force of the elastic element, and is also proportional to the deformation of the elasticity. Taking the S-type sensor as an example, when the sensor is subjected to tensile force P, the surface of the elastic element has a strain gage
Because the strain of the elastic element is proportional to the size of the external force p, the strain gauges are connected to the measuring circuit, and the output voltage can be measured to determine the force size. For tensile strength testing machine sensors, general use of differential full-bridge measurement, will be pasted strain gauges to form the Bridge Road, R1, R2, R3, R4, the actual value of the equivalent of 4 (or 8) strain gauges, that is, R1=R2=R3=R4, when the sensor is subjected to external forces (tension or pressure), The sensor elastic element produces the strain and causes each resistance value to change, its change value is R1, R2, R3, R4, the result originally balanced bridge, now unbalanced, Bridge Road has voltage output, set E e= [r1r2/(R1+R2) 2] r1/r1-r2/r2+ R3 /r3-r4/r4) U-type middle u for external power supply bridge voltage further fluidized with E=[R2/4R2] (r1/r-r2/r+ r3/r-r4/r) u will ri/ri=kεi on behalf of the E=[UK/4] (ε1-ε2+ε3-ε4)
Simply put, the external force P causes deformation of the strain gauges inside the sensor, resulting in the imbalance of the bridge, resulting in the electronic tensile testing machine sensor output voltage changes, we can know the magnitude of the force by measuring the output voltage changes. In general, the output signal of the sensor is very faint, usually only a few MV, if we measure this signal directly, it is very difficult, and can not meet the high precision measurement requirements. Therefore, the weak signal must be amplified by the amplifier, the amplified signal voltage can reach 10V, when the signal is an analog signal, The analog signal is transformed into a digital signal via a multi-switch and A/D conversion chip, and then the data is processed, at which point the strength measurement of the adhesion test machine is over.
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