15
IM 701957-01E
6 Calibrating Using a Shunt Resistor
Calculation Example
• When Determining the Corresponding Shunt Resistance (Rs) from the Strain (
ε
)
Given a gauge factor (K) of 2,
Detailed equation
Rs = R
×
(1–
ε
)/(2
×
ε
)
(6)
(equation B)
General equation
Rs = R
×
(1–2
×
ε
)/(2
×
ε
)
(7): Error of 1 to 2% present
(equation A)
Desired Strain
Derived by the Detailed Equation (6)
Rs value (
Ω
) Derived by the
ε
(
µ
STR)
Rs Value (
Ω
)
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 Corresponding Strain (e) from the Shunt Resistance (Rs)
If we derive e from equation (6) and (7),
Detailed equation
ε
= 1/(1+2
×
Rs/R)
(8)
(equation B)
General equation
ε
= 1/{2
×
(1+Rs/R)}
(9): Error of 1 to 2% present
(equation A)
When the Bridge Resistance R is 120 W
RS Value (
Ω
)
Strain
ε
(
µ
STR) Derived by
Strain
ε
(
µ
STR) Derived by
the Detailed Equation (8)
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 W
RS Value (W)
Strain
ε
(
µ
STR) Derived by
Strain
ε
(
µ
STR) Derived by
the Detailed Equation (8)
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
For the procedures related to performing the shunt CAL, see the manual that came with
the strain module that you are using.
Shunt CAL may not operate correctly on some strain measurement instruments. Check
this with the manual that came with the strain measurement instrument.
