Model |
1210 |
1215 |
1220 |
1230 |
1240 |
Products |
VW Spot weldable strain gage |
VW Soilnail
strain gage |
VW Weldable strain gage |
VW Shotcrete strain gage |
VW Concrete embedment strain gage |
Main uses |
Measurement of strain in
steel member
after spot welding/or epoxy potting |
Measurement of strain in
steel member
after arc welding |
Measurement of strain in
tunnel shotcrete |
Measurement of strain in
mass concrete |
Range
(με: microstrain) |
3,300 |
3,000 |
3,000 |
3,000 |
Initial setting value(Hz) |
2,100 |
900 |
1,800 |
900 |
Gage Factor
(GㆍF) |
0.3911 |
4.062 |
0.7756 |
3.304 |
Coefficient of linear expansion |
11 × 10-6 strain/℃ (where, 10-6 = 0.000001) |
Readout unit |
Readout and Data logger which can measure VW sensor or any products of any company can be interchanged, and when you use the readout which has the rate of transformation mode, measuring with the rate of transformation which has the same Gage Factor is very convenient. If it doesn't has the rate of transformation mode or you use the Readout which was produced by other companies, measure it by Hz or μsec and substitute a following calculation formula. |
[ Calculation method ]
Section |
In case of measuring
by frequency Mode(Hz) |
In case of measuring
by period Mode(μsec) |
Calculating strain(με) |
GㆍF × 10-3 × F2
GㆍF = Gage Factor
10-3 = 0.001
F = Measured value by Hz(Frequency) |
GㆍF × 10-3 ÷ N2
GㆍF = Gage Factor
10-3 = 0.001
N = Measured value by μsec(period) |
Calculation of real(Δ) strain(με) |
Current(με) - initial(με) - (Tcc-Tcs) × (Tcurrent-Tinitial)
Tcc : Coefficient of linear expansion of concrete (10×10-6/℃)
Tcs : Coefficient of linear expansion of metal goods (11×10-6/℃)
Tcurrent : Measured values of current temperature
Tinitial : Measured values of initial temperature |
Correction temperature |
1. When the long term measurement or the precision measurement is needed, as above calculation formula, you have to revise temperature to reduce an error by an expansion coefficient.
2. In the case of steel materials and concretes, when their temperature is not stable, you can make a mistake that stress is strong by temperature's instability.
3. In the case of steel materials, as the sensors' expansion coefficient and steel materials' expansion coefficient is same, you don't need to revise the temperature of the sensors. |
[ Calculation of stress or press ]
Stress
(σ:kg/cm2) |
σ = Δμε × 10-6 × E
Δμε = Current(με) - initial(με)
E = Elastic modulus of object material (kg/cm2) |
Press
(P:kg) |
P = σ × A
A= Area of object (cm2) |
Elastic modulus of metal : 2.1 × 106 (= 2100000 kg/cm2)
Elastic modulus of concrete : Must confirm correctly the concrete elastic modulus, because it is various from 1.4 × 105 to 2.6 × 105(g/cm2). |
[ Calculation example ]
| Install the device of vibration rate of transformation that can be attached by welding on a metal plate that has area of 300cm2 (elasticity coefficient: 2.1×106kg/cm2), and then measure the incipient value(1,000Hz) and the present value(1,050Hz). And you can find out press(kg/cm2) and load(kg) as the following.
* Microstrain(με) = GㆍF × 10-3 × F2 = 4.062 × 0.001 × 10502 = 4478.35
1. Real microstrain(Δμε) = Current strain(με) ― Initial strain(με) = 4478.35 - 4062 = 416.35
2. Stress(σ:kg/cm2) = Δμε × 10-6 × E = 416.35 × 0.000001 × 2100000 = 873.43
3. Press(P:kg) = σ × A = 873.43 × 300 = 262300.5 |
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