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
 
· Strain Gages
· Piezometers
· Water Pressure(Water Level)
· Soil Pressure
· Displacement
· Temperature
· Inclinometers
· Settelment
· Testing Meters
· Calibration Devices
· Datalogger Devices
· Datalogger System
· Cables and Attachments
· Mud-Rock Flow Monitoring System
 
On Jan, 2009, our company has moved to the new address where locates in the city-centre district of Nanjing. The improvement of our working environment will propel the development of our company. Furthermore, the convenient traffics help us to fulfill a better after-sale service. NGN Instrument, Inc. expects your visiting!
 
Products
 

Model VWR Vibrating Wire Rebar Meter

 

1Application

Model VWR Vibrating Wire Rebar Meter is applicable to be embedded in hydraulic or other concrete structures to measure the inner rebar strain. Meanwhile, the temperature value of the embedding point can be measured. By adding accessories, it can be constituted to be anchor dynamometer, baserock strain gauge and so on instruments that measure the strain. This rebar meter has the intelligent identification function.

2Technical Specifications

 

R-20

R-25

R-28

R-32

R-36

R-40

Size

Rebar Diameter d (mm)

20

25

28

32

36

40

Cross Sectional Area

of steel tube A (cm2)

3.14

4.90

6.30

8.05

10.2

12.6

Length of steel tube L (mm)  

120

 

 

Perfor

mance

Range

Stretching (MPa)

300

Compressing(MPa)

200

Sensitivity k (MPa/F)

≤0.10

Accuracy (F.S)    

 ±0.1%

Temp. 1 Measure. 2 Range ()

 -40+150

Temp. Measure. Accuracy()

 ±0.5

Water Pressure Resistance (MPa)

 ≥1

Insulation Resistance ()

 ≥50

Remark: Frequency Modulus F= Hz2×10-3

1: Temperature

2: Measurement

 

3The Theory of Operating

3.1Constitution 

Model VWR Vibrating Wire Rebar Meter consists of strain transducer, connecting steel covers (standard parts), signal transmission cable, etc.

3.2Mechanism

The rebar meter suffers the stretching or compressing when the inner rebar of the measured structure has the changing of the strain. Then the steel cover will be deformed synchronously. The deformation will let the rebar meter sense the stretching or compressing deformation. And then this deformation is transferred to the vibrating wire to change to the changing of the strain. Thus the vibration frequency of the vibrating wire will be changed. The electromagnetic coils excite the vibrating wire and measure the vibration frequency. The frequency signal is transferred to the readout device via cable. As the result, the suffered strain of the rebar inside the measured structure will be obtained. Meanwhile, the temperature value of the embedding point can be measured.

3.3Calculation

  a)The strain value σ has a linear relationship with the output frequency modulus F as the gauge is bearing the axial deformation under environmental temperature as constant:

                             ε= kF

                            F = F - F0

Herewith,

k: Sensitivity with the unit of 10-6/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 gauge is not affected by external force, 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:

                       σ´= kF´+ bT = 0

                    kF´= -bT

                     T = T - T0

Herewith,

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

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

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

T0: Reference temperature value with the unit of ;

  c)The gauge setteled in the hydraulic or other concrete structures is subject to the effects of deformation and temperature. Thus, the general calculation formular is:

                σm = kF + b′T = k (F - F0)+ b(T - T0)

Herewith,

σm: Strain value of the measured structure with the unit of MPa;

Remark:

The Rebar Meter has the automatic temperature compensation. Experiment shows that the temperature correction coefficient is smaller than the minimal reading value, and the calculation formula a) is applicable for general situation.


 

 
Back
 
 

 NGN Instrument, Incorporated Email: njgn@njgn.com 
 26 Majiajie street Website: www.njgn.com
 Nanjing, Jiangsu Tel:86(25)84443850/1/2/3
 CHINA 210009 Fax:025-58705973 
 Copyright ©1998-2013 NGN Instrument, Incorporated. All Rights Reserved.