Select and use strain gauge

 There many kind of strain gauge with different performance. We should consider many reasons to select and use the best strain gauge, first, we need to consider the terms of experiment and usage(Use precision,Environment conditions: temperature,humidity, atrocious environments, interference, stick area, install condition, specification of the materials etc., ); Second, we should consider the parameters of the goods(Expansion Coefficient, Elastic Modulus, Forced or Stress Distribution etc.,). The ways to select and use as below:

一、The principles:

1.  Types to select.

We should select strain guage according to the tested purpose, the materials and precision demands of the tested goods. For example, the sense organ of the load cell , then it need to select the Foil strain gauge which is small P andθ; If the sensitivity of the load cell need to be large,then we should select Semiconductor strain gauge;  We should select Foil strain gauge if we test the dynamic weighing.

2. The fundus materials of the Sensitive Grids.

How to select the best and suitable Sensitive Grids or fundus materials? First, we should according to the environment, temperature, tested time and the utimate straining, then we also need to condider the precision demand of the strain gauge, like if test goods in normal temperature, in long time, and the largest straining below 10, then you need to use CuNi,     strain gauge; and if in mid-tempperature, used NnCrAlCu alloy,    strain gauge; In normal temperature, the high precision load cell usually use CuNi alloy or NnCrAlCu alloy

3. The resistance of strain gauge.

We consider and select the resistance of strain gauge according to the demands which  the test equipment require to the resistance and sensitivity of strain gauge etc..For example, in the stress test, we usually use 120Ω strain gauge to match the resistance equipment; To the load cell, we use high resistance (350Ω、500Ω、1000Ω even larger etc..) to improve its stability and sensitivity, sometimes we also consider the performance and the values and the function, we use high resistance strain gauge.

4. Dimension of strain gauge.

We decide the dimension of strain gauge according to the materials, stress and the sticked area.For example, we use longer grids strain gauge if the stress is proportional or the changing is small, and it allow to stick on a larger area, in this condition, we suggest to use 3-6mm’s grids; but we use the grids length≤1mm, if the stress is collected in area or the sticked area is small. The long grids strain gauge is good for stick, connection and good cool function, it also can improve the performance of the strain gauge. The dimension of the strain gauge is smaller,the demands of  sticked quality are higher,and the cool function is weaker, so on conditions of insure the precision and have enough sticked area, it is better to use long grids strain gauge.

5. The configuration of the Sensitive Grids.

We select the configuration of the Sensitive Grids according to the stress and other demands. Like when the main stress is unknown or shear strain, then we can select multi-axes strain gauge, We use these strain gauge which Triaxial angle are 45°、60°or 120°for the first sitution; and use Triaxial angle is 45°for another sitution. If we test the known stress strain, then we can select Uniaxial strain gauge; the circle multi-axes strain gauge is used in Pressure sensor.

6. Temp. self-compensation and Elastic Modulus self-compensation.

We should select different Temp.self-compensation or Elastic Modulus self-compensation strain gauge according to its materials, working Temp.and the precision. Like some common steel or spring steel, then use Temp. self-compensation strain gauge with the 11×10-6/℃ expansion coefficient; and to the Aluminium alloy, then use strain gauge with the 23×10-6/℃ expansion coefficient.

7. Creep Grade.

The user should select the matching Creep Grade according to the configuration,capacity and Elastomer of the load cell. First time we can select one or two kind of diffenent Creep Grade’s strain gauge to test, and according to the last test data,then select the best Creep Grade.