Appendix
Calculation Example
When Determining the Shunt Resistance (Rs) from the Strain (ε)
Given a gauge factor (K) of 2,
Detailed equation (equation B) Rs = R × (1 − ε)/(2 × ε) .........................(6)
General equation (equation A) Rs = R × (1 − 2 × ε)/(2 × ε) ...................(7) Degree of error of 1 to 2%
Desired Strain
ε (μSTR)
Rs Value (Ω) Derived from
the Detailed Equation (6)
Rs Value (Ω) Derived from
the General Equation (7)
R = 120 Ω R = 350 Ω R = 120 Ω R = 350 Ω
1 000 59 940 174 825 59 880 174 650
2 000 29 940 87 325 29 880 87 150
5 000 11 940 34 825 11 880 34 650
10 000 5 940 17 325 5 880 17 150
When Determining the Strain (ε) from the Shunt Resistance (Rs)
If we derive ε from equations (6) and (7),
Detailed equation (equation B) ε = 1/(1 + 2 × Rs/R) ..............................(8)
General equation (equation A) ε = 1/{2 × (1 + Rs/R)} ............................(9) Degree of error of 1 to 2%
• When the Bridge Resistance R is 120 Ω
RS Value (Ω) Strain ε (μSTR) Derived from
the Detailed Equation (8)
Strain ε (μSTR) Derived from
the General Equation (9)
60 000 999 998
30 000 1 996 1 992
12 000 4 975 4 950
6 000 9 901 9 804
• When the Bridge Resistance R is 350 Ω
RS Value (Ω) Strain ε (μSTR) Derived from
the Detailed Equation (8)
Strain ε (μSTR) Derived from
the General Equation (9)
180 000 971 970
90 000 1 941 1 937
36 000 4 838 4 814
18 000 9 629 9 537
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