混凝土应变的测量
混凝土应力的测量
混凝土温度的测量
混凝土开合度测量
岩石应变量的测量
钢筋应力值的测量
渗透水压力的测量
测压管水压力测量
水库水位值的测量
锚索预应力的测量
静荷载承压力测量
结构表面应变测量
结构位移量的测量
结构倾斜量的测量
刚性构件应变测量
土体应变量的测量
土体应力值的测量
土体多点位移测量
土体多点沉降测量
土体分层沉降测量
地基多点位移测量
地基水平位移测量
地基垂直位移测量
自动采集测量数据
 
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Products
 

Model VWD Vibrating Wire Displacement Meter

 

1 Application

Model VWD Vibrating Wire Displacement Meter is applicable to measure the extension/deformation of hydraulic structures or other concrete structures. It also can be used to measure the displacement, settlement, strain, sliding of structures such as the soil dams, soil embankment, side slopes and so on. Meanwhile, it also measures the temperature of the embedding point synchronously. By adding accessories, it can be formed to be the Baserock Displacement Meter, Multiple point Extensometer, Earth Strain Gauge and so on instruments which measure the deformation. And this gauge has the intelligent identification function.

2 Technical Specifications

 

VWD-20

VWD-50

VWD-100

Measurement Range (mm)

020

050

0100

Sensitivity k (mm/F)

≤0.01

≤0.02

≤0.04

Accuracy (F.S)

±0.1%

±0.1%

±0.1%

Temperature Range ()

-40+150

-40+150

-40+150

Temperature Accuracy ()

±0.5

±0.5

±0.5

Outer Diameter (mm)

30.5

30.5

30.5

Length (mm)

300

340

400

Water Pressure Resistance (MPa)

≥1

≥1

≥1

Insulation Resistance (MΩ)

≥50

≥50

≥50

Remark: Frequency Modulus F= Hz2×10-3

3 Theory of Operation

3.1 Constitution

The model VWD Displacement Meter consists of Cardan joints, stainless steel protecting tube, two-level mechanical negative amplification mechanism, signal transmission cable, vibrating wire and excited electromagnetic coils,                         

3.2 Mechanism

The deformation of the measured structure will cause the displacing of the displacement meter. Then it is transferred to the two-level mechanical negative amplification mechanism. The negative amplified displacement value is transferred to vibrating wire and it turns to be the changing of the strain. Thus the vibration frequency is changed. And the electromagnetic coils excite the vibrating wire and measure the vibration frequency. Afterwards, the frequency signal is transferred to the readout device via cable. As the result, the displacement value of the measured structure is thereby obtained. Meanwhile, temperature of the embedding point can also be measured synchronously.

3.3 Calculation

  a) The displacement value L has the following linear relationship with the output frequency modulus F when the displacement meter is only bearing the axial deformation under the outside environmental temperature as constant.

                              L = kF

                            F = F - F0

Herewith,

k: Sensitivity with the unit of mm/F;

F: Difference between the measured real-time value and the reference one with the unit of F;

F: Real-time measured value with the unit of F;

F0: Reference value with the unit of F.

  b)When the displacement meter is not affected by external force (gauge length between both ends is unchanged), there is an output value F´ if the temperature is increased by T. This output is only caused by the changing of the temperature, thus it should be deducted in calculation.

Experiment shows that F´ and T has the following linear relationship:

                      L´= kF´+ bT = 0

                    kF´= -bT

                     T = T - T0

Herewith,

b: Temperature correction coefficient with the unit of mm/;

T: Difference between the measured real-time value and the reference one with the unit of ;

T: Real-time measured temperature value with the unit of ;

T0: Reference temperature value with the unit of ;

  c)The displacement meter settled in the hydraulic or other concrete structures is subject to the effects of deformation and temperature. Thus, the general calculation formula is:

                Lm = kF + bT = k (F - F0) + b(T - T0)

Herewith,

Lm: Deformation value of the measured structure with the unit of mm;

Remark:

The material linear expansion coefficient of the sensible measurement component is close to the fixed machine framework. Experiment shows the temperature correction coefficient is very small and thus generally the calculation formula a) can be used.

 
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